Evolution & Variation in Human Diet, Energy Expenditure & Metabolism       ARCHIVE

https://mindandmatter.substack.com/p/early-access-diet-hunting-culture?utm_source=publication-search 

I. Mind and Matter Podcast Overview and Host Background by Eugene Morin

1. The Mind and Matter podcast explores how food, drugs, and ideas influence human development, featuring insights from top scientists and thinkers.

   • The podcast delves into how the mind and body react to various inputs, drawing from the host's extensive scientific background.

   • The host, with a PhD in neuroscience focusing on neuroendocrinology and behavior, uses their expertise to interpret complex scientific discussions.

2. The podcast host spent a decade in academia conducting scientific research before starting the Mind and Matter podcast.

   • Their academic journey included specializing in molecular, developmental, and evolutionary genetics.

   • This background enables the host to effectively translate and integrate scientific findings from podcast guests.

3. In addition to the podcast, the host produces long-form written content inspired by episodes and a free weekly newsletter.

   • The newsletter includes upcoming guest information, links, and commentary on scientific studies.

   • The written content integrates insights across episodes, offering deeper analysis of discussed topics.

4. The podcast relies on audience support through paid subscriptions to the Mind and Matter Substack for sustainability.

   • For $5 a month, subscribers gain early access to episodes, full transcripts, and prioritized responses to questions.

   • Support can also come from purchasing products from affiliate partners, which offer discounts and help fund the podcast.

5. The podcast aims to provide information from primary sources, such as researchers, and is not intended as medical advice.

   • It focuses on knowledge from those actively producing new scientific insights.

   • Listeners are encouraged to share episodes to help grow the podcast's reach through word-of-mouth.

II. Guest Background and Research Focus

6. The guest, Eugene Morin, is a paleoanthropologist specializing in animal bones, primarily in Europe, focusing on France and Montenegro.

   • He has been researching for about 20 years, concentrating on Neanderthals and early modern humans.

   • His work emphasizes diet, subsistence, foraging, ethnography, and ethnohistory to interpret past human behaviors.

7. Morin’s research primarily focuses on humans from 200,000 to 50,000 years ago, with some studies extending to 600,000 years ago.

   • This period encompasses the Lower, Middle, and Upper Paleolithic.

   • He occasionally studies later periods but focuses mainly on the later Paleolithic.

III. Paleolithic Era Definition and Timeline

8. The Paleolithic era spans from about 3.3 million years ago, when cultural objects first appeared, to 12,000 years ago, with the advent of agriculture.

   • It began in Africa with the creation of tools designed to assist human activities.

   • The era ended in the Near East with the emergence of agricultural practices.

9. The Paleolithic was characterized by a hunter-gatherer lifestyle with no agriculture.

   • Humans relied on foraging and hunting for sustenance throughout this period.

   • The absence of agriculture defined the subsistence strategies of Paleolithic populations.

10. Human migration during the Paleolithic started in Africa, with expansions to Southeast Europe and Asia around 2.5 million years ago.

• By 2 million years ago, humans reached Southeast Asia, followed by Australia (45,000–60,000 years ago) and the Americas (25,000–30,000 years ago).

• Early hominids, possibly early Homo populations, began these migrations, though their exact classification is debated.

IV. Physical Adaptations in Homo

11. Early Homo species grew taller than Australopithecines, approaching modern human height.

• This increase in stature was evident before their migration out of Africa.

• Their postcranial skeleton showed features similar to modern humans, facilitating movement.

12. A key adaptation in Homo was a significant increase in brain size, occurring later in human evolution.

• Tools were used long before large brains developed, contrary to earlier assumptions.

• Brain enlargement is a hallmark of Homo evolution, distinguishing it from other mammals.

13. Humans developed a high capacity to sweat, enabling heat dissipation during prolonged activities.

• This adaptation prevented overheating during extended physical exertion, unlike many mammals.

• For example, cheetahs can sprint but cannot sustain activity due to heat buildup.

14. Humans have a higher proportion of slow-twitch muscle fibers, supporting endurance over power.

• Slow-twitch fibers rely on oxygen for sustained activity, unlike fast-twitch fibers used for sprinting.

• This contrasts with chimpanzees, which have more fast-twitch fibers, making them stronger but less enduring.

15. These adaptations enabled humans to engage in long-distance running, crucial for hunting and scavenging.

• The ability to run for extended periods gave humans a niche in pursuing large prey.

• Stamina, rather than power, was selected for, distinguishing humans from other mammals.

V. Digestive and Metabolic Adaptations

16. Human stomach pH is similar to that of wolves and hyenas, suggesting an adaptation for scavenging.

• This low pH allows humans to process partially rotten meat, similar to other scavengers.

• Unlike vultures, humans cannot tolerate extremely low pH for highly decayed meat.

17. The human gut likely enlarged to process complex carbohydrates, possibly linked to increased plant consumption.

• Fire use, starting around 400,000–500,000 years ago, helped reduce plant toxins through cooking.

• This adaptation may have facilitated the digestion of a broader range of plant-based foods.

18. Evidence of fire use is robust from 400,000 years ago, though occasional use may date back to 2 million years ago.

• Regular fire use was mastered by multiple Homo species, including Homo erectus.

• Earlier fire use is debated due to the ephemeral nature of archaeological evidence.

VI. Diet and Hunting in the Paleolithic

19. Early humans hunted medium-sized game like gemsbok and antelope, with scavenging likely for larger animals.

• Archaeological evidence shows tool marks on bones from 2.5 million years ago, indicating marrow extraction.

• Medium-sized animals, similar to caribou, were within the hunting capabilities of early humans.

20. Meat was likely more than an occasional treat, as evidenced by frequent tool marks on bones.

• Marrow extraction for fat was a primary incentive, as fat was more valued than muscle tissue.

• The presence of cut marks suggests meat was a regular part of the diet by 500,000 years ago.

21. Isotopic studies indicate early hominids ate mostly plants, with meat becoming more significant in Neanderthals and Homo sapiens.

• Neanderthals are described as hyper-carnivorous, though this may be an exaggeration.

• By 500,000 years ago, meat was a staple in human diets, based on isotopic evidence.

22. Cave art, starting around 50,000–60,000 years ago, often depicted animals, suggesting their cultural significance.

• Early cave art included dots and hand stencils, with animal depictions appearing around 40,000–45,000 years ago.

• The focus on large animals like bison and cave lions may reflect hunting or symbolic importance.

VII. Neanderthal and Homo sapiens Interactions

23. Neanderthals and Homo sapiens coexisted for at least 50,000 years in regions like Southeast Europe and the Near East.

• Genetic evidence shows introgression, indicating interbreeding between the two populations.

• Stone tools from both groups are indistinguishable, suggesting cultural exchange.

24. Neanderthals and Homo sapiens had similar diets, focusing on the same animals and fat sources.

• Both transported marrow and subcutaneous fat, showing comparable subsistence strategies.

• In southern Europe, nuts may have supplemented fat intake for both groups.

25. Interbreeding between Neanderthals and Homo sapiens was likely rare but sufficient to prevent complete genetic divergence.

• Gene exchange occurred perhaps once per generation, maintaining some genetic similarity.

• Modern humans carry Neanderthal genes, evidence of this limited interbreeding.

26. Neanderthal extinction around 35,000–40,000 years ago may be linked to environmental factors rather than cultural inferiority.

• A climatic deterioration around 45,000 years ago likely reduced Neanderthal population sizes.

• Small population sizes may have led to genetic collapse due to insufficient gene flow.

VIII. Neanderthal Culture

27. Neanderthals used symbols, as evidenced by raptor claw ornaments with cut marks, suggesting symbolic use.

• These claws, from large birds like vultures and eagles, were not edible, indicating non-utilitarian purposes.

• Over 30 European sites show consistent use of raptor claws, excluding other animals’ claws.

28. Neanderthals used mineral pigments like ochre and manganese, possibly for body decoration.

• Pigments are found from France to South Africa, indicating widespread use.

• Some evidence links pigments to bone tools, suggesting decorative applications.

29. Neanderthal cave art, including hand stencils and dots, dates to around 50,000 years ago.

• This art predates modern human presence in some regions, indicating Neanderthal creation.

• Recent challenges suggest possible modern human incursions, but this remains controversial.

30. Neanderthal burial sites, like those at La Chapelle-aux-Saints, indicate intentional burial practices.

• Fully articulated skeletons contrast with scattered faunal remains, supporting deliberate burial.

• Some argue these burials lack symbolic meaning, but this is debated as a double standard compared to modern human burials.

IX. Cultural and Cognitive Evolution

31. Neanderthal cognitive abilities were underestimated, but recent evidence shows symbolic behavior and speech capacity.

• Over the past 50 years, research has shifted to recognize Neanderthals’ complex cognitive abilities.

• Symbolic artifacts like raptor claws and cave art challenge earlier assumptions of cognitive inferiority.

32. The idea of a single “Paleolithic diet” is considered nonsense by archaeologists due to regional dietary diversity.

• Diets varied based on local flora and fauna, with some regions lacking plants or large game.

• Human flexibility in diet was a key adaptation, contradicting the notion of a uniform diet.

33. Endurance hunting was likely common due to humans’ physiological adaptations for stamina.

• Ethnographic records show endurance hunting across diverse environments, from tundras to tropics.

• This method had higher success rates by exhausting prey, leveraging human heat dissipation and slow-twitch fibers.

34. Communal hunting was significant, requiring cooperation and creating collective action problems for meat distribution.

• Ethnographic studies highlight communal hunts targeting gregarious species like bison, increasing success rates.

• These hunts necessitated social coordination, likely driving the evolution of cooperation.

35. Socialization and cooperation were key to human survival, distinguishing Homo sapiens from other mammals.

• Humans shared food with non-kin, a rare behavior among mammals.

• Cooperation in hunting and plant knowledge transmission enhanced survival and cultural development.

X. Ethnography and Ethnohistory Insights

36. Ethnographic studies reveal that recent hunter-gatherers are not static proxies for ancient ones due to colonial impacts.

• Colonization reduced large game populations and altered hunting practices, like horse use in North America.

• Early firearms were less effective than bows, affecting traditional hunting methods.

37. Endurance hunting was underestimated until recent ethnohistorical research revealed its global prevalence.

• Initially considered marginal, it was found in diverse environments like boreal forests and tropical settings.

• Its decline coincided with the introduction of rifles, which changed hunting dynamics.

38. Native knowledge of animals was extensive, but metapopulation-level impacts were hard to assess.

• Local knowledge guided hunting decisions, but large-scale population trends were not considered.

• Rituals ensured animals “returned,” reducing concerns about extinction.

39. Rituals and spiritual beliefs may have served to reduce stress and secure hunting success.

• Sympathetic magic helped manage the uncertainty of food procurement in harsh environments.

• These practices had emotional and cultural roles, potentially aiding survival.

40. Modern cultural constructs, like three meals a day, would seem strange to many hunter-gatherers.

• Some groups ate sporadically or had variable meal patterns, unlike modern schedules.

• Hygiene obsession, such as sterile environments, contrasts with hunter-gatherer practices.

XI. Changing Perspectives in Paleoanthropology

41. The assumption that the Middle Paleolithic was exclusively Neanderthal has been challenged.

• Recent findings suggest possible modern human incursions, prompting a reevaluation.

• This shift reflects the dynamic nature of paleoanthropological interpretations.

42. The discovery of the “hobbit” (Homo floresiensis) in Southeast Asia was a surprising find.

• Its Australopithecine-like features at 50,000–100,000 years ago defied expectations.

• This discovery highlighted the diversity of hominid species in recent prehistory.

43. DNA studies have revealed Neanderthal kinship patterns, such as patrilocality, previously thought unknowable.

• Males stayed in groups while females migrated, a pattern identified through genetic analysis.

• This finding opened new avenues for understanding social structures in the Paleolithic.

44. The importance of dietary fat over muscle tissue was a significant shift in understanding hunter-gatherer diets.

• Ethnographic accounts emphasize fat, like marrow, as a primary nutritional goal.

• Western focus on meat overlooked this preference, altering dietary interpretations.

45. Rotten meat consumption, once considered taboo, is now recognized as a common practice among hunter-gatherers.

• Ethnographic evidence shows preference for maggot-filled meat for easier digestion.

• This challenges modern biases and highlights dietary adaptability.

XII. Modern Implications and Research Directions

46. Studying human evolution influences modern dietary perspectives, questioning cultural constructs like food spoilage.

• Awareness of hunter-gatherer practices reduces concerns about consuming “high” meat.

• It highlights how cultural norms shape modern food preferences.

47. Collective action problems in hunting highlight challenges in managing endangered species today.

• Without metapopulation data, hunter-gatherers lacked the concept of extinction.

• This informs modern conservation efforts, emphasizing the need for scientific data.

48. Current research by Morin focuses on rethinking hunting models beyond the stereotype of individual spear hunters.

• Ethnography reveals a range of context-specific hunting methods.

• This aims to create richer, more accurate models of Paleolithic hunting practices.

49. The past was more varied than modern forager studies suggest, necessitating ethnohistorical perspectives.

• Accounts from missionaries and travelers reveal lost practices and diversity.

• Simplistic models of population replacement overlook this complexity.

50. Human flexibility and adaptability were key to surviving diverse environments.

• Regional variations in diet and hunting reflect humans’ ability to adapt to local conditions.

• This adaptability likely contributed to Homo sapiens’ global success.

XIII. Additional Key Points

51. Early hominids used tools before significant brain enlargement, challenging earlier assumptions.

• Tools date back to 3.3 million years ago, predating large brains by millions of years.

• This suggests cognitive complexity developed alongside tool use, not after it.

52. Slow-twitch muscle fibers enabled humans to outlast prey in endurance pursuits.

• Unlike fast-twitch fibers in other mammals, these supported prolonged activity.

• This adaptation gave humans a competitive edge in hunting large game.

53. Fire use by 400,000 years ago facilitated dietary shifts by detoxifying plants.

• Cooking reduced plant toxins, expanding the range of edible flora.

• This likely supported the dietary flexibility of Homo species.

54. Neanderthal extinction may have been driven by ecological factors, not competition with Homo sapiens.

• Climatic changes reduced habitable areas, isolating Neanderthal populations.

• Small populations were vulnerable to collapse without sufficient gene flow.

55. Cave art’s symbolic meaning remains debated, possibly reflecting hunting, fear, or spiritual beliefs.

• Depictions of large animals may symbolize power or cultural significance.

• Early art’s sophistication suggests advanced cognitive abilities in both species.

56. Communal hunting required complex social coordination, fostering human cooperation.

• Driving prey toward designated areas increased hunting success rates.

• This likely reinforced social bonds and group survival strategies.

57. Ethnographic records highlight the impact of colonization on traditional hunting practices.

• Introduction of horses and firearms altered how game was procured.

• These changes disrupted long-standing ecological balances.

58. Neanderthal symbolic artifacts, like raptor claws, suggest cultural sophistication.

• Their selective use indicates intentional symbolic or ornamental purposes.

• This challenges earlier views of Neanderthals as culturally inferior.

59. The absence of a universal Paleolithic diet underscores human dietary adaptability.

• Diets varied by region, from plant-heavy to meat-focused, based on availability.

• This flexibility allowed humans to thrive in diverse environments.

60. Mental stamina, possibly culturally transmitted, complemented physical stamina in hunting.

• Ethnographic accounts describe teachings of persistence in pursuit of prey.

• This mental toughness was critical for endurance hunting success.

61. Warfare in the Paleolithic likely selected for running ability in both genders.

• Running was essential for survival in competitive resource conflicts.

• Ethnographic evidence shows women were trained to run for safety.

62. Hunter-gatherer rituals around animals reflect a belief in their regeneration.

• Respectful treatment was thought to ensure animals’ return, negating extinction concerns.

• This worldview supported sustainable hunting practices.

63. The skeletal record shows less robust bones with agriculture, linked to reduced mobility.

• Increased plant consumption led to more dental cavities.

• Genetic adaptations, like lactose tolerance, emerged post-agriculture.

64. Neanderthal and Homo sapiens stone tools suggest cultural diffusion or convergence.

• Indistinguishable tools indicate shared techniques or knowledge transfer.

• This complicates distinguishing the two groups archaeologically.

65. The concept of extinction was foreign to hunter-gatherers due to their spiritual beliefs.

• Rituals ensured animals’ souls returned, perpetuating their presence.

• This limited awareness of long-term population declines.

66. Early spears, dating to 300,000–400,000 years ago, were key hunting tools.

• Evidence of bow and arrow use is indirect, possibly from 60,000 years ago.

• Traps and snares, though likely used, leave little archaeological trace.

67. Ethnographic studies reveal diverse meal patterns among hunter-gatherers.

• Unlike modern three-meal schedules, some ate sporadically or once daily.

• This variability challenges modern assumptions about eating habits.

68. Rotten meat consumption reflects human digestive adaptability to scavenging.

• Ethnographic examples show preference for maggot-filled meat for taste and digestion.

• This aligns with humans’ low stomach pH, similar to scavengers.

69. Paleoanthropology has shifted from viewing Neanderthals as primitive to recognizing their complexity.

• Evidence of art, burials, and ornaments supports their cognitive sophistication.

• This challenges biases favoring Homo sapiens’ uniqueness.

70. Human evolution was shaped by cooperation, flexibility, and environmental adaptation.

• Socialization and dietary versatility enabled Homo sapiens to outlast other hominids.

• These traits, rooted in Paleolithic practices, continue to define human resilience.

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GROK

I. Adaptable by Herman Pontzer - Human metabolism is significantly higher than that of other primates.

Humans burn approximately 20% more calories per day than chimpanzees and bonobos, even when controlling for body size.

This higher metabolic rate allows humans to support energetically expensive traits like larger brains and longer lifespans.

II. Life history reflects energy expenditure differences across species.

Life history encompasses the pace of development, reproduction, and aging, all of which require energy.

Variations in energy expenditure shape how quickly organisms grow, reproduce, and age.

III. Humans exhibit a metabolic paradox with high fertility and long lifespans.

Despite high reproductive rates and large babies, humans live longer than other primates.

This paradox is supported by a higher total energy expenditure, providing more energy for these costly traits.

IV. The human brain is energetically expensive.

The human brain consumes about 300 kilocalories per day, equivalent to running a 5K daily.

This high energy demand distinguishes humans from other apes with smaller brains.

V. Smaller gut size in humans may free up energy for other functions.

A 1995 paper by Leslie Aiello and Peter Wheeler proposed that humans evolved smaller guts to allocate energy to larger brains.

Reduced gut size is linked to a diet including meat and cooked foods, which are easier to digest.

VI. Total energy expenditure includes all calories burned daily.

Total energy expenditure encompasses basal metabolic rate, digestion, and activity energy expenditure.

Over half of daily energy is spent on background physiological tasks like maintaining the immune system and heartbeat.

VII. Basal metabolic rate accounts for the majority of energy expenditure.

Basal metabolic rate represents about 60% of daily energy use, even in active individuals.

It covers essential functions like maintaining organ activity during rest or sleep.

VIII. Activity energy expenditure includes more than physical movement.

Activity energy expenditure includes overt movement and heightened nervous system activity, such as during mental engagement.

For example, chess players burn significant calories due to mental alertness, not just physical activity.

IX. Doubly labeled water is a precise method for measuring total energy expenditure.

This isotope-tracking technique measures carbon dioxide production to calculate daily calorie burn.

It allows organisms to go about their daily routines without lab confinement.

X. Humans have a higher total energy expenditure than other great apes.

Studies using doubly labeled water show humans burn more calories daily than orangutans, gorillas, chimpanzees, and bonobos.

This was measured in captive apes to ensure comparable activity levels.

XI. Orangutans have one of the lowest metabolic rates among mammals.

Orangutans’ metabolic rates are lower than most placental mammals, except for sloths and pandas.

This low rate contrasts with humans’ high-energy metabolism.

XII. Body size affects metabolic rate, following Kleiber’s law.

Larger animals burn more calories due to having more cells, but the relationship is not linear.

A tenfold increase in body size results in about seven times more energy expenditure.

XIII. Humans carry more body fat than other apes.

Healthy human males carry 15-25% body fat, and females 20-30%, compared to less than 10% in apes.

This higher fat mass misled early studies into underestimating human metabolic rates.

XIV. Fat-free mass is a better measure for metabolic comparisons.

Fat-free mass excludes metabolically inactive fat, providing a more accurate measure of metabolic size.

Differences in fat proportions between humans and apes necessitate this adjustment.

XV. Hunting and gathering provided humans with a metabolic advantage.

The combination of hunting animal foods and gathering plant foods increased dietary energy availability.

Sharing food within groups maximized the benefits of both food types.

XVI. Cooking enhances energy extraction from food.

Cooking increases the energy yield per bite, supporting humans’ high metabolic demands.

This complements the hunting and gathering strategy.

XVII. Other apes cannot adopt human dietary strategies.

Unlike humans, other apes lack the social and technological adaptations for hunting and gathering.

This limits their ability to increase metabolic rates like humans.

XVIII. Human guts are smaller due to dietary shifts.

The human large intestine is smaller than in other apes, reflecting a diet with less fibrous plant material.

This is inferred from fossil evidence like rib cage shape.

XIX. Humans evolved an external nose for water conservation.

The external nose helps recapture water vapor from breath, reducing water loss.

Humans use about one-third less water than expected for their body size compared to other apes.

XX. Humans require daily water intake, unlike other apes.

Other apes obtain sufficient water from plant foods, while humans need to drink due to drier diets and higher activity.

This adaptation suits humans’ active lifestyles in varied climates.

XXI. Human stomach pH is highly acidic, resembling scavengers.

Human stomach acid is more acidic than that of carnivores or herbivores, similar to vultures.

This likely evolved to kill bacteria in rancid meat consumed by early humans.

XXII. Early humans likely consumed rancid meat.

Ethnographic accounts show traditional populations worldwide ate putrid meat.

This suggests scavenging was a significant dietary strategy in human evolution.

XXIII. The genus Homo emerged with dietary and anatomical changes.

Around 2.5 million years ago, stone tools and smaller teeth indicate a shift toward more animal-based foods.

These changes correlate with larger brains and tool-making abilities.

XXIV. Sharing food was critical to human evolution.

Evidence like cut marks on large animal bones suggests food sharing among early hominins.

This social behavior enhanced the benefits of hunting and gathering.

XXV. Metabolic flexibility allows humans to process diverse foods.

Humans can digest a wide range of foods, reflected in smaller guts and versatile teeth.

This adaptability supports a mixed diet of plants and animals.

XXVI. Traditional hunter-gatherer diets vary by environment.

Populations near the equator eat a balanced mix of plants and animals, while those near the poles consume more animal foods.

This variation reflects food availability in different climates.

XXVII. Arctic populations are relatively recent adaptations.

Humans only inhabited Arctic regions full-time about 8,000 years ago, less ancient than farming.

This challenges claims that high-meat diets are ancestral for all humans.

XXVIII. Dietary adaptations can occur relatively quickly.

Genetic adaptations, like lactose tolerance, show humans can adapt to new diets in 10,000 years.

Non-genetic adaptations, like microbiome changes, can also facilitate dietary shifts.

XXIX. Ketosis is not a default state for traditional populations.

Measurements in the Hadza show no evidence of ketosis, even during low-carb periods.

Arctic populations like the Inuit have evolved to resist ketosis despite high-fat diets.

XXX. Carnivorous animals do not always enter ketosis.

Species like dogs, which eat high-meat diets, often avoid ketosis through gluconeogenesis.

This challenges assumptions that meat-heavy diets inherently lead to ketosis.

XXXI. Obesity is primarily driven by diet, not exercise.

Exercise is crucial for health but does not significantly reduce body weight alone.

Caloric intake is the primary factor influencing fat gain or loss.

XXXII. Hadza hunter-gatherers burn similar calories to sedentary Westerners.

Despite higher physical activity, the Hadza burn comparable calories to Americans when adjusted for body size.

This suggests the body adapts to conserve energy despite activity levels.

XXXIII. Exercise reduces metabolically expensive processes.

Increased exercise lowers immune function, inflammation, and stress hormone production.

These reductions free up energy for physical activity without increasing total expenditure.

XXXIV. Reproductive hormones decrease with high exercise.

High physical activity lowers testosterone and estrogen levels, contrary to popular belief.

This is a healthy adaptation to limited energy availability.

XXXV. Overtraining can disrupt hormonal balance.

Excessive exercise, as in Olympic athletes, can suppress hormones excessively, leading to health issues.

This represents the extreme end of energy allocation trade-offs.

XXXVI. Ultra-processed foods drive overeating.

Populations consuming more ultra-processed foods have higher body fat percentages.

Their palatability encourages overconsumption despite satiety signals.

XXXVII. Caloric source does not significantly affect body weight.

Fat, carbohydrate, and protein calories have similar effects on body weight once consumed.

The key difference lies in how foods affect satiety and eating behavior.

XXXVIII. Palatability influences overeating.

Highly palatable foods like potato chips encourage continued eating compared to less palatable foods like broccoli.

This is due to sensory enjoyment overriding satiety signals.

XXXIX. Ultra-processed foods are defined by complex ingredients.

They involve multiple ingredients and processing steps, unlike whole foods like vegetables or home-made bread.

This complexity contributes to their hyper-palatability.

XL. Energy expenditure increases with economic development.

People in developed countries burn more calories due to larger body sizes.

This counters the assumption that sedentary lifestyles reduce energy expenditure.

XLI. Basal metabolic rate is slightly higher in less developed countries.

Higher pathogen loads in less developed countries increase basal metabolic rate slightly.

This effect is small compared to within-population variability.

XLII. Lifestyle has minimal impact on energy expenditure.

Hunter-gatherers and sedentary populations show similar energy expenditure when adjusted for body size.

This indicates metabolic adaptations balance activity levels.

XLIII. Energy expenditure explains little of obesity differences.

Global variations in energy expenditure account for only about 10% of obesity differences.

Dietary intake is the primary driver of body fat differences.

XLIV. Genetic predisposition affects obesity risk.

Genes expressed in the brain influence hunger and satiety, affecting obesity likelihood.

Some individuals are naturally more resistant to weight gain.

XLV. GLP-1 and GIP drugs aid weight loss.

These drugs reduce hunger and reward sensitivity, helping control overeating.

They mimic natural hormones and show a promising safety profile.

XLVI. Weight loss drugs require careful monitoring.

Despite their promise, long-term effects of GLP-1 and GIP drugs need ongoing evaluation.

Obesity’s health risks may justify their use in severe cases.

XLVII. Diet is the primary lever for weight loss.

Reducing caloric intake is more effective than exercise for weight loss.

High-fiber and high-protein diets promote satiety, aiding calorie control.

XLVIII. Intermittent fasting works by reducing calories.

Time-restricted feeding reduces overall caloric intake, not through metabolic magic.

It can be an effective strategy for some individuals.

XLIX. Personal dietary preferences vary widely.

Individual tolerances, like lactose or gluten intolerance, do not dictate universal dietary rules.

Diets should be tailored to personal needs and satiety responses.

L. Body fluency empowers better health decisions.

Understanding how bodies work helps individuals make informed lifestyle choices.

This knowledge fosters constructive discussions on health and societal issues.

ERNIE

I. Understanding Energy Expenditure and Metabolism

Title: Adaptable
Author: Herman Pontzer

• Total Energy Expenditure (TEE) in Humans vs. Other Primates:

  • Humans burn 20% more calories daily compared to chimpanzees and bonobos, even after accounting for body size.

  • This higher energy expenditure supports our larger brains, longer lifespans, and higher reproductive rates.

• Basil Metabolic Rate (BMR) Differences:

  • Humans have a higher BMR than other apes, which means we burn more calories just to maintain basic bodily functions.

  • This higher BMR is partly due to our larger fat-free mass, which is more metabolically active than fat tissue.

• Impact of Physical Activity on Energy Expenditure:

  • Despite being more physically active, hunter-gatherers like the Hadza burn the same number of calories per day as sedentary Westerners when adjusted for body size.

  • The body adjusts to increased physical activity by reducing energy expenditure on other processes like immune function and stress reactivity.

• Diet and Energy Intake:

  • The primary factor in weight gain and obesity is energy intake, not energy expenditure.

  • Ultra-processed foods, which are high in calories but low in satiety, contribute significantly to overeating and weight gain.

• Metabolic Flexibility and Diet:

  • Humans have a unique ability to switch between burning fats and carbohydrates for energy, known as metabolic flexibility.

  • This flexibility allows us to adapt to a wide range of diets, from high-fat to high-carb, without compromising our energy balance.

• Evolutionary Adaptations in Human Diet:

  • The shift to hunting and gathering around 2.5 million years ago marked a significant change in human diet, leading to increased consumption of animal foods.

  • This dietary shift was accompanied by anatomical changes, such as smaller teeth and guts, and physiological adaptations, like a higher BMR.

• Hunter-Gatherer Diets:

  • Traditional hunter-gatherer diets vary widely depending on the environment, ranging from high-animal food diets in the Arctic to high-plant food diets near the equator.

  • Despite these differences, all hunter-gatherer populations exhibit a remarkable ability to maintain energy balance and avoid obesity.

• Role of Sharing in Human Evolution:

  • Sharing food, especially meat, played a crucial role in human evolution by allowing early humans to access a wider range of nutrients and energy sources.

  • This cooperative behavior also facilitated the development of social bonds and cultural practices that are unique to humans.

• Water Conservation in Humans:

  • Humans have evolved to conserve water more efficiently than other apes, which is reflected in our lower water turnover rates.

  • This adaptation is thought to be related to our ability to survive in diverse environments, including arid regions where water is scarce.

• Impact of Economic Development on Energy Expenditure:

  • People in more developed countries tend to have higher TEE due to their larger body size, but when adjusted for body size, there is little difference in energy expenditure between populations.

  • The small differences in energy expenditure between populations are largely due to variations in BMR, which can be influenced by factors like pathogen load and immune function.

• Genetic Factors in Obesity:

  • Genetic studies have identified several genes that are associated with obesity, many of which are expressed in the brain and affect hunger and satiety signaling.

  • These genetic factors can influence an individual's likelihood of developing obesity, but lifestyle factors like diet and exercise still play a significant role.

• Effectiveness of Weight Loss Drugs:

  • New classes of weight loss drugs, such as GLP-1 and GIP agonists, have shown promise in helping individuals lose weight by reducing hunger and increasing satiety.

  • These drugs mimic hormones that are naturally produced in the body and have a relatively safe profile, but long-term monitoring is necessary to ensure their safety and effectiveness.

• Importance of Diet Quality:

  • The quality of the diet, including the balance of macronutrients and the presence of fiber and protein, plays a crucial role in weight management and overall health.

  • High-fiber and high-protein foods can help increase satiety and reduce overall calorie intake, making it easier to maintain a healthy weight.

• Role of Fasting and Time-Restricted Feeding:

  • Fasting and time-restricted feeding can be effective strategies for weight loss by reducing overall calorie intake.

  • These approaches can be particularly useful for individuals who struggle with portion control or late-night snacking.

• Metabolic Health and Disease Prevention:

  • Maintaining a healthy weight and metabolic function is crucial for preventing chronic diseases like diabetes, heart disease, and certain types of cancer.

  • Regular physical activity, a balanced diet, and adequate sleep are all important factors in maintaining metabolic health and reducing the risk of disease.

• Adaptability of the Human Body:

  • The human body is remarkably adaptable, capable of thriving in a wide range of environments and dietary conditions.

  • This adaptability is a result of millions of years of evolution and has allowed humans to become one of the most successful species on the planet.

• Future Directions in Obesity Research:

  • Ongoing research is needed to better understand the complex interplay between genetics, lifestyle, and environmental factors in obesity.

  • By gaining a deeper understanding of these factors, researchers can develop more effective strategies for preventing and treating obesity.

• Practical Tips for Weight Management:

  • For individuals looking to lose weight, focusing on diet quality, portion control, and regular physical activity are key strategies.

  • Incorporating high-fiber and high-protein foods, staying hydrated, and getting enough sleep can also support weight loss efforts.

• Role of Technology in Health Monitoring:

  • Advances in technology, such as wearable devices and breath analyzers, are making it easier for individuals to monitor their metabolic health and track their progress.

  • These tools can provide valuable insights into how diet and exercise affect the body, helping individuals make more informed decisions about their health.

• Importance of a Holistic Approach to Health:

  • Achieving and maintaining good health requires a holistic approach that considers diet, exercise, sleep, stress management, and social connections.

  • By addressing all of these factors, individuals can improve their overall well-being and reduce their risk of chronic disease.

Evolution and Variation in Human Metabolism

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The podcast episode features Dr. Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University and author of "Adaptable," who discusses human metabolism and evolution. He explains the "human paradox," where humans, despite having large brains, long lifespans, and larger, more frequent offspring compared to other apes, exhibit higher total energy expenditure. Dr. Pontzer explores historical and current theories about this, including the "expensive tissue hypothesis" (smaller gut leading to bigger brains), and his own research using doubly labeled water to measure energy expenditure in various populations. The discussion also covers human adaptations to diet, fat storage, and the impact of modern lifestyles on health and obesity, emphasizing the discrepancy between exercise and weight loss.

I. Human Diet and Its Influence on Mind and Body Title: Evolution Variation in Human Diet Energy Expenditure Metabolism Author: Herman Pontzer

Whether food, drugs, or ideas, what you consume influences who you be.

We learned together from the best scientists and thinkers alive today about how your mind body reacts to what you feed it.

II. Herman Pontzer's Professional Background

I'm Herman Poner, a professor of evolutionary anthropology and global health at Duke University.

He is also the author of a new book called Adaptable.

III. The Premise of "Adaptable"

Adaptable is all about how your body works and why you ought to care.

Many big topics wrestled with in society today fundamentally rest on how we understand our bodies and how they work differently.

IV. Herman Pontzer's Academic Identity

I would consider myself a physiologist, basically a physiologist who works on humans.

In today's academia in the US, if you work on humans, you're either in a medical program or an anthropology program.

V. Definition of Life History

Life history is the pace at which an organism develops, grows up, reproduces, grows old, and eventually dies.

This pace of life is something that evolves, such as shorter or longer development periods.

VI. Interrelation of Life History and Energy Expenditure

To grow up takes energy, to reproduce takes energy, and to keep your body from breaking down as you grow older all take energy.

We can think about life history and energy expenditure as really tightly related phenomena.

VII. Energy Allocation Trade-offs in Organisms

There's only so much energy an animal is going to be able to obtain, create, and utilize.

If a species allocates a lot to reproduction, producing many babies early in life, there is less energy left over for other things.

VIII. The Human Paradox in Life History

Humans have a lot of babies compared to other creatures like us, such as other primates.

Despite having bigger babies with extended developmental periods and living a long time, the expected energy trade-offs are not seen in humans.

IX. Energetically Expensive Human Traits

Humans have long lives and many big babies compared to other apes, both of which take energy.

The human brain is incredibly expensive, burning 300 kilocalories a day, which is equivalent to running a 5K every day.

X. The Traditional Expensive Tissue Hypothesis

The classic idea, dating back to the 1800s, posits that to evolve a big brain, humans had to evolve a smaller gut.

This idea became canon after a significant 1995 paper by Leslie Aiello and Peter Wheeler.

XI. Mechanism of the Expensive Tissue Hypothesis

Different organs burn calories at different rates, with brains, digestive tracts, and liver being energetically expensive.

Humans evolved a smaller gut, likely because they eat meat (easier to digest, more energy-dense) and cooked food, freeing up energy for big brains.

XII. Limitations of the Expensive Tissue Hypothesis

The 1995 paper did not focus on the fact that humans have bigger babies and more of them.

It also did not address the lifespan issue, which is known to be energetically expensive.

XIII. Definition of Total Energy Expenditure (TEE)

Total energy expenditure is all the calories your body burns over a 24-hour period.

It includes everything from background physiological tasks like immune system function and heartbeat to noticeable activities like moving around and digesting food.

XIV. Definition of Basal Metabolic Rate (BMR)

More than half of the energy burned daily is for the background basic stuff your body does to keep you alive, even while sleeping.

This lowest level of maintenance energy expenditure is called your basal metabolic rate.

XV. Major Components of Daily Calorie Expenditure

About 60% of your energy expenditure, even for active people, is spent on basic body maintenance not involving movement or exercise.

Another 10% or so of your daily calories burned goes to digesting your food.

XVI. Activity Energy Expenditure Includes More Than Movement

The leftover chunk of energy expenditure, not BMR or digestion, includes a lot of movement but also other activities.

Being alert, aware, and engaged, such as talking, increases energy expenditure above basal metabolic rate and is lumped into activity.

XVII. Doubly Labeled Water Technique for TEE Measurement

To measure total energy expenditure, researchers use a technique called doubly labeled water, which is an isotope tracking method.

This is the only way to precisely measure total daily energy expenditures outside of a laboratory setting.

XVIII. Practical Advantages of Doubly Labeled Water

The doubly labeled water technique allows for measuring energy expenditure during normal daily life without being confined or hooked up to contraptions.

Researchers only need a couple of urine samples over a week or two weeks to gather the necessary data.

XIX. Comparative TEE in Great Apes and Humans

Researchers measured total energy expenditures in all great ape genuses, including orangutans, gorillas, chimpanzees, and bonobos, all captive.

When accounting for body size, humans burn 20% more energy every day; our metabolic rates are just faster.

XX. Humans as the "High Energy Ape"

Humans have the fastest metabolic rate and are considered the high energy ape compared to all other ape relatives.

Orangutans have one of the lowest metabolic rates ever measured for any placental mammal, excluding sloths and pandas.

XXI. The Relationship Between Metabolic Rate and Body Size (Kleiber's Law)

All cells burn energy constantly for their daily functions, so more cells mean more energy burned.

The total energy burned daily increases with metabolic rate to the .75 power, following a power law known as Kleiber's law since the 1930s.

XXII. Necessity of Body Size Control in Metabolic Analysis

It is crucial to control for body size in any analysis of energy expenditure because species like bonobos and chimpanzees are much smaller than humans, while male gorillas are much bigger.

This control must be done smartly because the relationship between metabolic rate and body size is a power law curve, not one-to-one.

XXIII. Higher Human TEE as an Explanation for Expensive Traits

Controlling for body size, humans have about 20% higher total energy expenditure compared to other apes.

This higher energy availability provides a physiological explanation for how humans can afford energetically expensive traits like large brains, numerous offspring, and long lifespans.

XXIV. Fat-Free Mass as a Key Metabolic Measure

Fat-free mass is the body mass minus fat, and it is a better measure for metabolic comparisons than total body weight.

Fat is metabolically quiet, burning hardly any energy, making it a poor indicator of metabolic size.

XXV. Humans Are the Fattest Ape

Humans carry a lot of fat and are not only the highest energy ape but also the fattest ape.

A healthy adult human male might carry between 15% and 25% body fat, while females might carry 20% to 30%.

XXVI. Leanness of Other Apes

Even sedentary apes in zoos typically carry 10% or less body fat, making them very lean.

Their large potbellies are due to their big digestive systems, not fat.

XXVII. Humans Have a Higher Basal Metabolic Rate

When carefully and correctly accounting for body size differences and distinguishing between total body mass and fat-free mass, humans also have a higher basal metabolic rate.

This suggests a generally faster metabolic rate across human physiology.

XXVIII. The Cost of High Energy Availability

If having more energy is so good, the question arises why other apes don't also ramp up their metabolic rates.

The answer is that having more energy available is also a cost, requiring more food to fuel the higher metabolic rate.

XXIX. Hunting, Gathering, and Sharing as Human Energy Acquisition Strategy

Humans gain extra energy through hunting and gathering, combined with sharing, forming a mixed portfolio of food acquisition.

This strategy allows for the benefits of both carnivore and plant-eater diets, contributing to human success.

XXX. Dietary Contrasts: Apes vs. Humans

Plant eaters, such as chimpanzees and gorillas, pursue low-risk, low-reward foods like leaves and fruit, which offer less energy per unit of time.

Meat, in contrast, provides much more energy than plant foods.

XXXI. The Critical Role of Sharing in Human Diet

Relying solely on meat is risky because hunters often come home empty-handed.

Sharing plant and animal foods maximizes benefits, ensuring calories are available even when hunts are unsuccessful.

XXXII. Hunter-Gatherer Activity Levels Compared to Western Humans

Even a sedentary human with a desk job, getting 5,000 to 10,000 steps, can be considered quite active compared to a chimpanzee in the wild.

Chimpanzees in the wild often sit and rest a lot, covering only a couple of kilometers a day.

XXXIII. Origin of Genus Homo and Dietary Shift

The major change launching the genus Homo, around 2.5 million years ago, was the advent of hunting and gathering.

Archaeological evidence like stone tools and cut marks on animal bones indicates frequent hunting.

XXXIV. Anatomical Changes Correlated with Dietary Shift in Homo

The shift to hunting and gathering is correlated with anatomical changes, such as tooth size getting smaller, presumably because foods require less chewing.

These changes, along with an increase in brain size and association with stone tools, define the origin of the genus Homo.

XXXV. Human Gut Size Reduction

Human guts became somewhat smaller, specifically the large intestine, as our ancestors shifted away from purely fibrous plant diets.

While no fossilized intestines exist, reconstruction of rib cage and belly shapes supports this reduction.

XXXVI. Evolution of the External Human Nose for Water Conservation

An external nose began to evolve in early Homo, preserving bone structures visible in skulls.

This adaptation helps conserve water because water vapor in breath can recollect against the internal surfaces of the nose when breathing out.

XXXVII. Human Water Conservation and Daily Water Needs

Humans are water conservers, using about one-third less water than expected for their body size compared to other apes.

Unlike most apes who get sufficient water from plants in humid forests, humans need to drink water daily because their foods are drier and they are more physically active in hot climates.

XXXVIII. Refuting the Aquatic Ape Hypothesis

The fact that human bodies are built to conserve water contradicts the aquatic ape hypothesis, which suggests humans evolved in freshwater environments.

It makes little sense for a species constantly in water to have evolved mechanisms for water conservation.

XXXIX. Human Stomach pH Indicates Scavenging Adaptation

Humans have an incredibly low, very acidic stomach environment.

Our stomach acidity resembles that of scavengers like vultures, rather than carnivores or herbivores.

XL. Historical Practice of Eating Rancid Meat

Ethnographic accounts from the 1500s and 1600s, and even modern observations of groups like the Hadza, show people eating rancid and putrid meat across the globe.

This widespread practice suggests it was a general characteristic of human diet for a long time.

XLI. Low Stomach pH for Bacterial Killing

The primary reason for such an extremely low stomach pH in humans is likely to kill bacteria.

While low pH aids protein digestion, the even lower acidity compared to carnivores suggests a specific adaptation for bacterial defense.

XLII. Global Diversity in Traditional Hunter-Gatherer Diets

Ethnographic accounts of over 200 hunter-gatherer populations worldwide show an incredible mix of animal and plant food intake.

Diet varies geographically, with warmer climates featuring more plant foods and arctic environments favoring more animal foods.

XLIII. The Recent Adaptation of Inuit Diets

Full-time human presence in the Arctic only dates back about 8,000 years, making the Inuit diet a relatively recent adaptation.

This timeline means the Inuit diet is less ancient than farming as a model for human dietary origins.

XLIV. Rapid Metabolic Adaptation: Lactose Tolerance

Adaptations to specific nutrients can happen relatively quickly if there's sufficient evolutionary pressure.

The ability to digest milk as an adult (lactose tolerance) evolved quickly after the development of dairy farming, independently in Northern Europe and Northern Africa.

XLV. Absence of Ketosis as a Standard State in Traditional Populations

There is no evidence that ketosis is the standard normal state of affairs for any traditional population, including the Hadza where it has been measured.

Even populations on high-protein, high-fat, very low-carb diets, such as some Arctic groups, have adaptations to prevent readily entering ketosis.

XLVI. Exercise as an Ineffective Tool for Weight Loss

Exercise is crucial for health but does not correlate easily with body weight control.

By itself, exercise is a pretty poor tool for trying to reverse obesity and does not work for most people seeking weight loss.

XLVII. Surprising Energy Expenditure of Hadza Hunter-Gatherers

Hadza hunter-gatherers, despite being much more physically active, burn the same number of calories per day as average Americans or Europeans.

This finding was surprising because the Hadza get more physical activity in a day than most Americans get in a week.

XLVIII. Body's Metabolic Adjustment to Physical Activity

Human bodies adjust to lifestyles, so even with increased physical activity, the total calories burned might not increase as much as expected.

Increased exercise can lead to lower basal metabolic rates, reduced inflammation from immune function, and decreased stress reactivity, which are all metabolically expensive processes.

XLIX. Diet as the Primary Driver of Obesity

Body weight is fundamentally a balance between calories eaten and calories burned.

Since variation in energy expenditure only explains a small fraction of obesity differences, the rest must be attributed to energy intake and diet.

L. Ultra-Processed Foods Correlate with Obesity

The most obese populations, those with the highest body fat percentages, are also eating the most ultra-processed food.

Analyses based on available literature show a clear correlation between the percentage of ultra-processed food in a community's diet and body fat percentages.

1. Introduction: Understanding the Human Body Through an Evolutionary Lens

Herman Pontzer's work centers on understanding "how your body works and why you ought to care." He emphasizes that many societal questions, from diet to health, fundamentally rely on our understanding of human biology and its variations. Pontzer, a physiologist working on humans within an anthropology framework, uses his background to unravel the complexities of human metabolism and its evolutionary trajectory, often comparing humans to other primates.

2. Life History and the "Human Paradox"

2.1. Defining Life History and Energy Expenditure

• Life History: "the pace at which an organism any organism develops, grows up and then reproduces... and then grows old and eventually dies." This pace is a product of evolution and is intrinsically linked to energy expenditure.

• Energy Expenditure: The total energy an organism expends to grow, reproduce, maintain bodily functions, and physically interact with its environment. There are inherent trade-offs in energy allocation; more energy invested in one area (e.g., reproduction) often means less for others (e.g., longevity).

2.2. The Human Paradox

Humans present a "human paradox" because they seem to defy typical life history trade-offs seen in other animals, particularly other apes:

• High Fertility: Humans have "a lot of babies compared to other creatures like us, like other primates."

• Large Offspring: Human babies are "bigger" and have "extended developmental periods."

• Long Lifespan: Despite high reproductive costs, humans "live a long time."

• Expensive Traits: Humans possess other energetically demanding traits:

• Big Brains: The human brain "burns 300 kilocalories a day," equivalent to a 5K run daily, making it "incredibly expensive."

• Higher Physical Activity: Historically (and even today, compared to wild apes), humans are "more physically active... than other apes are."

• "It seems like all of the kind of traits that make us different from other apes and special are energetically expensive all of them."

This paradox suggests that humans somehow access or utilize "extra energy."

3. Traditional Explanations and the "Expensive Tissue Hypothesis"

3.1. The Classic Idea: Gut-Brain Trade-Off

The prevailing explanation for the energetically expensive human brain, prior to Pontzer's work, was the "expensive tissue hypothesis," popularized by Iello and Wheeler (1995):

• Smaller Gut: To support a large brain, humans evolved a "smaller gut," specifically a smaller large intestine.

• Dietary Shift: This gut reduction was enabled by a shift to a "more energy dense" diet, particularly "meat," which is "easier to digest." More recently, cooking food is also considered a factor.

• Energy Reallocation: The energy saved from a smaller, less metabolically demanding digestive tract was "freed energy up for something else," which in humans was directed towards evolving "big brains."

• Limitations: This hypothesis primarily focused on brain size and did not fully account for other expensive human traits like increased fertility or longevity.

4. Measuring Energy Expenditure: Vocabulary and Techniques

4.1. Key Terms

• Total Energy Expenditure (TEE): "all the calories that your body burns over a 24-hour period," encompassing all physiological tasks, movement, and digestion.

• Basal Metabolic Rate (BMR): The "background basic stuff that your body does to keep you alive," representing over half of daily energy expenditure, even for active individuals. It's the "lowest level of of just maintenance energy expenditure."

• Activity Energy Expenditure (AEE): The energy spent on movement and other forms of engagement beyond BMR and digestion. This includes overt physical activity (e.g., exercise) but also cognitive alertness (e.g., "talking to you... my nervous system tone is a little bit higher").

• Fat-Free Mass: Body mass minus fat mass. This is a crucial measure for metabolic comparisons because fat is metabolically "quiet" and doesn't burn much energy, unlike other tissues.

4.2. Doubly Labeled Water Technique

• This "isotope tracking technique" is the "only way to measure total daily energy expenditures outside of a laboratory setting."

• Individuals drink "isotopically enriched water," and the rates at which hydrogen and oxygen isotopes are flushed out via urine allow calculation of carbon dioxide production and, thus, calories burned. This method allows for measurement during "normal daily life," without restrictive lab conditions.

5. Human-Primate Metabolic Comparison: The High-Energy Ape

Pontzer's research using doubly labeled water to measure TEE in great apes (orangutans, gorillas, chimpanzees, bonobos) revealed a significant finding:

• Higher Human TEE: "humans are burning 20% more energy every day. Our metabolic rates are just faster." This holds true even "controlling for body size" (accounting for Kleiber's Law, which describes the non-linear relationship between metabolic rate and body size).

• "High Energy Ape": Humans have the "fastest metabolic rate" compared to all other ape relatives.

• Fatness: Humans are not only the "highest energy ape" but also the "fattest ape." A healthy human male carries 15-25% body fat, and a female 20-30%, whereas apes in zoos carry "10% or less body fat." This higher fat percentage in humans had previously misled some early BMR studies into thinking human metabolism was similar to apes.

• Higher Human BMR: When properly accounting for body size and fat-free mass, humans also exhibit a "higher basal metabolic rate" compared to other apes.

5.1. Implications of Higher Energy Expenditure

• Explaining the Paradox: This higher energy availability provides a physiological explanation for the "human paradox"—the ability to support big brains, long lives, and multiple large offspring without obvious energetic trade-offs. "More energy. That's that's the how."

• Why Not Other Apes?: Other apes do not "ramp up their metabolic rates" because doing so requires consistently obtaining "more energy" to "feed that machine every day."

6. The Evolution of Human Diet and Metabolism

6.1. The Advent of Hunting and Gathering

• Origin of Genus Homo: The "big change that really launches our genus" and differentiates us from other apes is "hunting and gathering," beginning "around 2 and a half million years ago."

• Archaeological Evidence: This shift is marked by the appearance of "stone tools" and "cut marks on animal bones" in archaeological sites.

• Anatomical Changes: Correlated anatomical changes include "tooth size getting smaller" (less chewing for fibrous plants) and "brain size getting a little bit bigger." This suite of changes defines the genus Homo.

• Importance of "And": Hunting "and" gathering is crucial, as "hunting and gathering don't work without sharing." Sharing diverse food sources (high-risk, high-reward meat and low-risk, low-reward plant foods) maximizes caloric intake and ensures consistency, launching "adaptations that we see in humans today."

6.2. Water Conservation and the External Nose

• Water Conservation: Humans are "water conservers," using "about a third less [water] than you'd expect for our body size compared to other apes."

• Dietary and Behavioral Drivers: Unlike most apes, who get sufficient water from humid plant-rich diets in low-activity forests, human diets are "drier (especially when we cook them)" and humans are "more physically active in hot climates," necessitating water drinking.

• External Nose: The evolution of an "external nose" in early Homo is thought to aid water conservation by allowing water vapor in breath to "recollect against the internal surfaces of your nose." This contrasts with the "aquatic ape idea," which Pontzer dismisses, arguing that water conservation adaptations would be counterintuitive for an aquatic environment.

6.3. Stomach pH and Scavenging

• Low Human Stomach pH: Humans have "incredibly low, very acidic stomach acid," resembling "scavengers" like vultures, rather than carnivores (e.g., cats) or herbivores.

• Interpretation: This highly acidic stomach is thought to primarily "kill bacteria," suggesting that early humans may have consumed "dead and rancid meat" to a significant degree, an observation supported by ethnographic accounts of various traditional populations worldwide eating putrid meat.

6.4. Metabolic Flexibility and Ketosis

• Dietary Adaptability: Humans are highly adaptable in their diet, consuming a wide "range of foods." This is evident in our teeth and guts.

• Ketosis Misconceptions:Not a Standard State: There is "no evidence that... ketosis being the standard normal state of affairs for any traditional population."

• Hodza Data: Measurements in the Hodza hunter-gatherer population do not show ketosis.

• Arctic Adaptations: Intriguingly, some high-protein, high-fat, very-low-carb Arctic groups (like the Inuit) have evolved "to prevent ketosis," suggesting adaptations for efficient gluconeogenesis rather than reliance on ketones.

• Starvation Response: Ketosis is observed in other apes (e.g., orangutans) during "starving" periods, indicating it's a general mammalian response to energy deficit, not unique to humans or high-meat diets.

• Dietary Choice vs. Natural State: While individuals can induce ketosis through diet, there's no evidence it represents a "natural" or universally healthy baseline for humans.

7. Obesity and Modern Human Metabolism

7.1. Critiquing the "Eat Less, Move More" Model

• Obesity as a Public Health Problem: Standard public health guidelines frame obesity as a "50-50 kind of problem" of diet and activity.

• Exercise's Limited Role in Weight Loss: While exercise is "really important for your health," it "doesn't correlate to... body weight control in a an easy way." Exercise "by itself is a pretty poor tool for trying to reverse obesity. Doesn't work for most people."

• Hadza Study: Pontzer's research on the Hodza hunter-gatherers, who are "much more physically active than the standard American adult," found they "burn the same number of calories as Americans do and Europeans do" when controlling for body size.

• Metabolic Adjustments: This "mind-blowing" finding suggests that the body "somehow adjust[s] to our lifestyles." When physical activity increases, the body reduces other "metabolically expensive things at baseline," such as:

• Immune Function: "background inflammation" gets "tamped down."

• Stress Reactivity: Cortisol and epinephrine responses decrease.

• Reproductive Hormones: Testosterone and estrogen levels tend to go down (though this can reach unhealthy extremes in "overtraining syndrome").

• Energy Reallocation: The energy saved from these baseline reductions is redirected to fuel physical activity, resulting in little to no change in TEE. "If I burn more with my muscles, then, you know, I'll just burn less with other stuff."

7.2. The Primacy of Diet in Weight Control

• Energy Balance: "your body weight really is a balance between how many calories you eat every day and how many calories you burn off."

• Dietary Energy is Key: Given the limited impact of activity on TEE, "the energy that you're eating, the dietary energy is really what's pushing obesity."

• Macronutrients and Satiety:Calorie Equivalence: In terms of pure body weight, "a fat calorie is going to do versus a carbohydrate calorie once it's in your bloodstream floating around it's just as likely to get burned or stored."

• Overeating Driver: The key difference between foods lies in their effect on satiety and palatability. "Eating higher fiber foods make you feel full on fewer calories. Higher protein foods can make you feel full on fewer calories." Highly palatable (often ultra-processed) foods "are actually built to be a little bit addictive" and override satiety signals, leading to overconsumption.

7.3. Ultra-Processed Foods

• Definition: Defined by "the number of ingredients and the way they're combined," often coming in "colorful package[s] and the ingredient list is a paragraph."

• Link to Obesity: In analyses across global populations, "the most obese populations the highest body fat populations are eating the most ultra processed food." This suggests a strong correlation between ultra-processed food availability/consumption and obesity rates.

• Mechanism: While not fully understood, the "hyper palatability" and impact on brain reward centers are considered major drivers of overeating, rather than insulin response or specific macronutrient ratios.

7.4. Global Energy Expenditure Study (PNAS Paper)

• Large-Scale Data: The Doubly Labeled Water database, an international collaboration, now contains "over 10,000 measurements" of TEE from diverse populations, from hunter-gatherers to individuals in developed countries.

• Key Findings:Body Size and Development: In "richer your country, the more developed the country you're in on average, the taller and heavier you are and the more body fat you carry." This also means people in more developed countries "burn more calories every day on average... because you're bigger."

• Limited Lifestyle Effect on TEE: When controlling for body size, there is "no clear evidence of lifestyle effects on any of this stuff." Hodza hunter-gatherers' TEE is "exactly like us men and women."

• Small BMR Effect: A very small effect of economic development on BMR was detected: "people in less developed countries probably because they have more like pathogens more germs that they're fighting every day... have higher basal metabolic rates." This slight increase in BMR in less developed countries only contributes a "tiny whisper" to overall TEE differences.

• Variability Within vs. Between Populations: "the variability within a population is much bigger than the differences between populations."

• Obesity Explanation: Variation in energy expenditure "at most... explains maybe a tenth of the obesity differences across the globe." The remaining 90% "must be intake and diet."

8. Practical Advice for Weight Management

• Prioritize Diet: "don't stop exercising. It's really important for a lot of aspects of health, but when you want to move the number on the bathroom scale, it's got to be diet."

• Focus on Satiety: Aim to "eat fewer calories without being miserable." High-fiber and high-protein foods can help achieve satiety on fewer calories.

• Dietary Flexibility: There's no single "human diet." "Any range of diets might work for any individual person." Individuals should "shop around and try" different approaches to find what works for them.

• Fasting: Intermittent fasting and time-restricted feeding are effective because "they cut how many calories you eat every day." They are "good strateg[ies] that they find easy to follow" for some individuals.

• Mindful Eating: Pay attention to habits like "snacking... while watching TV at night" that contribute to excess caloric intake.

• Weight Loss Drugs (GLP-1 and GIP): For those struggling with obesity despite lifestyle interventions, new weight loss drugs are "really promising" and "work by keeping your brain quiet and not... pushing you to overeat." They appear to reduce general "reward sensitivity," not just food rewards. While long-term monitoring is crucial, the benefits may outweigh the risks for individuals with serious obesity.

9. Genetic Predisposition to Obesity

• Genetic Influence: There is a genetic component to obesity, with individuals being "wired in a way that makes you less or more likely to struggle with that."

• Brain Wiring: Evidence "points to the brain and how the brain is wired as being... the organ where this is happening." This involves "hunger and satiety signaling and reward centers within the brain."

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Summary

This excerpt from the "Mind and Matter" podcast features an insightful conversation with Dr. Herman Pontzer, a professor of evolutionary anthropology and global health. The discussion delves into the intricacies of human metabolism and its evolutionary context, contrasting human physiology with that of other great apes. Key themes include the "human paradox"—how humans manage energetically expensive traits like large brains, long lifespans, and frequent reproduction—and the surprising finding that humans have a higher total daily energy expenditure than other apes, even when controlling for body size. The conversation also explores the impact of diet, particularly the shift to hunting and gathering and the consumption of animal foods, on human evolution and health, challenging common misconceptions about exercise and modern obesity. Dr. Pontzer emphasizes that while exercise is crucial for health, dietary intake, especially ultra-processed foods, is the primary driver of obesity, suggesting that modern lifestyle changes have profoundly altered our metabolic landscape.

Human metabolism is a complex system that dictates how our bodies use and burn energy, influencing our health, lifestyle, and evolutionary trajectory. Researchers study it by examining various components of energy expenditure, comparing humans to other species, and analyzing historical and modern dietary patterns.

Key Components of Metabolism and Measurement

Total Energy Expenditure (TEE) refers to all the calories your body burns over a 24-hour period, encompassing everything from basic physiological tasks to physical movement and food digestion. Its major components include:

• Basal Metabolic Rate (BMR): This accounts for more than half of daily energy expenditure and covers the background, maintenance physiological tasks to keep you alive, even while sleeping. It's the energy cost of running your body when not doing much.

• Digestion: Approximately 10% of daily calories are burned to break down and absorb food.

• Activity Energy Expenditure (AEE): This comprises the remaining energy, largely movement, but also includes other forms of engagement, such as being alert, talking, or shivering.

Measuring TEE accurately outside a lab setting is done using the doubly labeled water technique. This method involves drinking isotopically enriched water and measuring the rates at which hydrogen and oxygen isotopes are flushed out of the body through urine samples over a week or two, allowing for calculation of carbon dioxide production and, thus, calories burned.

Human Metabolism Compared to Other Apes

Research using doubly labeled water has revealed significant differences in human metabolism compared to other great apes (orangutans, gorillas, chimpanzees, and bonobos), even in captive settings.

• Higher Total Energy Expenditure: Humans burn approximately 20% more energy daily than chimpanzees and bonobos, and even more compared to gorillas, when accounting for body size. Orangutans, in contrast, have some of the lowest metabolic rates among placental mammals. This makes humans the "high energy ape".

• Higher Basal Metabolic Rate: Humans also exhibit a higher BMR than other apes, which becomes evident when properly accounting for body size and fat-free mass. Earlier studies were sometimes misleading because they didn't correctly adjust for body size or the significant differences in body fat.

• "Fattest Ape": Humans naturally carry a higher percentage of body fat (15-30% for healthy adults) compared to other apes, which typically have 10% or less, even in captivity. This higher fat mass means total body weight alone is not the best measure for metabolic comparisons; fat-free mass provides a more accurate representation of metabolically active tissue.

The Human Paradox and Evolutionary Adaptations

The "human paradox" refers to the fact that humans possess energetically expensive traits—long lives, many large babies with extended developmental periods, big brains, and historically higher physical activity—without obvious energy trade-offs seen in other species. The explanation is that humans simply have more energy available.

This increased energy availability is linked to major evolutionary shifts, particularly the advent of hunting and gathering around 2.5 million years ago, which marked the origin of the genus Homo.

• Dietary Shift: Our ancestors moved away from predominantly plant-based diets, common for early hominins for millions of years, towards incorporating more energy-dense animal foods.

• Smaller Gut: This shift, aided by easier-to-digest meat and eventually cooking, led to the evolution of a smaller digestive tract, particularly the large intestine, as less energy was needed for digestion.

• Food Sharing: The ability to share food between hunters and gatherers provided a critical metabolic boost, combining the benefits of low-risk plant foods with high-reward animal foods, ensuring a more consistent energy supply.

• Water Conservation: Humans also evolved adaptations for water conservation, such as an external nose, allowing us to thrive in hotter, drier environments while being more physically active. Unlike other apes, humans need to drink water daily because their foods are drier and they are more active.

• Stomach Acidity: Human stomachs are highly acidic, similar to scavengers like vultures, suggesting an adaptation for consuming potentially bacteria-laden or rancid meat. This indicates that eating rotten meat was likely a part of human diet in the past.

• Metabolic Flexibility: Humans exhibit remarkable metabolic flexibility, able to process a wide range of foods. However, despite popular assumptions, studies on traditional populations like the Hadza indicate that ketosis is not a standard or natural metabolic state for humans, even those on high-fat, high-protein diets like the Inuit. Some Arctic populations even show adaptations that prevent rapid ketosis.

Modern Human Metabolism and Obesity

In modern contexts, the global increase in obesity is primarily attributed to energy intake (dietary calories), rather than a significant reduction in energy expenditure.

• Activity vs. Expenditure: While modern populations are generally more sedentary than hunter-gatherers, studies show that total daily energy expenditure (TEE) in physically active hunter-gatherers (like the Hadza) is comparable to or even lower than that of sedentary Westerners, especially when adjusted for body size. This suggests that the body adjusts its energy budget: increased activity may lead to reduced energy expenditure in other background processes like immune function or stress reactivity, minimizing the overall change in TEE. Therefore, exercise alone is not a highly effective tool for weight loss.

• Dietary Impact: Calorie intake has increased in developed countries. Ultra-processed foods are strongly correlated with obesity rates. These foods, often engineered for hyper-palatability through specific combinations of ingredients and flavors, override satiety signals and encourage overeating.

• Genetics and Predisposition: There is evidence from genetic studies that individuals have varying predispositions to obesity, largely linked to brain wiring that influences hunger, satiety, and reward processing. This highlights that weight management is not solely about willpower but also involves complex biological mechanisms.

For weight loss, the primary focus should be on dietary changes that reduce caloric intake without leading to misery, which would hinder adherence. Strategies like consuming higher fiber and protein foods, or using time-restricted feeding, can aid satiety and reduce overall intake. Newer weight loss drugs, such as GLP1 and GIP drugs, are also showing promise by influencing brain-based hunger and satiety signals, and reducing reward sensitivity.

The evolution of the human diet has played a fundamental role in shaping our species, leading to unique anatomical, physiological, and metabolic adaptations that distinguish us from other primates.

Here's an overview of diet evolution in humans:

• Early Hominin Diet: For the first four to five million years after the human lineage split from chimpanzees and bonobos (around six or seven million years ago), our ancestors, such as Australopithecus afarensis (like the Lucy skeleton), predominantly consumed plants. Their large, sharp cheek teeth (molars) were well-suited for a plant-based diet, similar to modern gorillas who also have large, sharp plant-eating molars.
  
  

• The Major Shift: Hunting and Gathering: A significant change occurred approximately 2.5 million years ago with the origin of the genus Homo. This period saw the emergence of stone tools and other archaeological indicators suggesting that our ancestors began hunting frequently enough to incorporate animal foods into their diet. This marked the beginning of a hunting and gathering subsistence strategy, which fundamentally differentiated early humans from other apes.
  
  

  • Emphasis on "and": The "and" in "hunting and gathering" is crucial. While individual hunting or gathering occurred, the human strategy involved both, along with sharing of food resources. This mixed portfolio provided the benefits of both carnivory (energy-dense meat) and herbivory (reliable plant foods), a combination not utilized by other apes.

  • Role of Cooking: Cooking food also played a role in increasing the energy available per bite, making digestion easier and further contributing to the dietary shift.

• Correlated Anatomical and Metabolic Adaptations: The shift to hunting and gathering and a more diverse diet was accompanied by a suite of evolutionary changes:
  
  

  • Smaller Gut and Teeth: Humans evolved a smaller digestive tract, specifically the large intestine, and smaller teeth (molars). This "expensive tissue hypothesis" suggests that consuming easier-to-digest foods (like meat, which is more energy-dense, and later cooked food) reduced the energetic demands of the digestive system, freeing up energy for other metabolically expensive organs.

  • Bigger Brains: The energy "saved" from a smaller gut is hypothesized to have been redirected to fuel the growth of our large, energetically expensive brains. The human brain burns approximately 300 kilocalories a day, equivalent to running a 5K daily.

  • Higher Metabolic Rate: Humans exhibit a faster overall metabolic rate compared to other great apes. When controlling for body size, humans burn about 20% more energy per day than chimpanzees and bonobos, and even more compared to gorillas and orangutans. This includes a higher basal metabolic rate (the energy needed for basic maintenance functions). This increased energy budget is proposed as the physiological explanation for how humans can afford multiple energetically expensive traits simultaneously, such as long lifespans, large brains, and frequent reproduction with bigger babies, traits that appear to contradict typical life-history trade-offs seen in other species (the "human paradox").

  • Increased Body Fat: Humans are uniquely the "fattest ape," carrying significantly more body fat (15-30% for healthy adults) compared to other apes (10% or less, even in captivity). This evolved predisposition to store fat further supports an increased energy reserve for our demanding physiology.

  • External Nose and Water Conservation: The evolution of an external nose in early Homo is linked to water conservation. Humans consume about one-third less water than expected for their body size compared to other apes. This adaptation became crucial as humans started eating drier foods (especially cooked) and became more physically active in hot climates, unlike forest-dwelling apes who obtain most of their water from plants and live in humid environments.

  • Low Stomach pH: Human stomachs are remarkably acidic, similar to scavengers like vultures, but significantly more acidic than carnivores or herbivores. This low pH is thought to be an adaptation to kill bacteria, suggesting that human ancestors, at least to some degree, consumed less fresh or even rancid meat. Historical accounts of traditional populations worldwide, including the Hadza, confirm the consumption of meat considered "rancid" by Western standards.

• Dietary Flexibility in Modern Hunter-Gatherers: Despite the historical shift towards animal foods, traditional hunter-gatherer populations exhibit an incredible diversity in diet, with the mix of animal and plant foods varying significantly based on geography and resource availability.
  
  

  • Populations near the equator tend to eat a more balanced 50/50 mix of plants and animals, while those closer to the poles (like the Inuit) consume a much higher proportion of animal foods (e.g., 80% or more).

  • Humans demonstrate remarkable metabolic flexibility, adapting to a wide range of available foods.

  • Despite popular assumptions, there is no evidence that ketosis is a standard or natural state for traditional hunter-gatherer populations, even those consuming high-meat diets like the Inuit. In fact, some Arctic groups show adaptations that prevent ketosis. This suggests that metabolic flexibility does not necessarily mean constant shifting into ketosis as a default.

  • Adaptations to specific nutrients, like lactose tolerance in adults, can evolve relatively quickly (e.g., within a few thousand years) when there is sufficient evolutionary pressure, as seen with the development of dairy farming.

Energy expenditure refers to all the calories your body burns over a 24-hour period, encompassing every physiological task from background maintenance to physical movement and food digestion.

Here are the major components of energy expenditure:

• Basal Metabolic Rate (BMR): This is the lowest level of energy expenditure for basic maintenance functions, such as your immune system, heartbeat, and nervous system, even while sleeping. It accounts for more than half (around 60%) of your daily energy expenditure, even for active individuals. It is often referred to as resting metabolic rate or basal energy expenditure.

• Digestion: Approximately 10% of daily calories burned are used to break down food, absorb nutrients, and traffic them into cells.

• Activity Energy Expenditure (AEE): This component includes energy spent on overt movement, like playing basketball or walking, but also encompasses other forms of engagement, such as being alert, aware, or engaged in tasks like talking or playing chess. Shivering and the body's response to fear are also included in AEE, as they are not part of BMR measurements.

Measurement of Total Energy Expenditure (TEE)

Measuring TEE outside a laboratory setting was not possible until the 1980s. The most precise method for measuring total daily energy expenditure in a free-living context is the doubly labeled water technique. This isotope-tracking technique involves drinking water enriched with hydrogen and oxygen isotopes. By measuring the rates at which these isotopes are flushed from the body over one to two weeks through urine samples, researchers can calculate carbon dioxide production and, consequently, calories burned. This method allows individuals to go about their normal daily lives without being confined or hooked up to equipment.

Energy Expenditure in Humans vs. Other Apes

Humans present a "paradox" in terms of life history and energy expenditure. While there are typically trade-offs where allocating more energy to one aspect (like reproduction) leaves less for others (like longevity), humans exhibit traits that are all energetically expensive yet co-exist:

• Long Lifespan: Humans live a long time.

• High Reproduction: Humans have many babies, and they are larger than those of other apes, requiring significant energy.

• Large Brains: The human brain is incredibly expensive, burning 300 kilocalories daily, equivalent to running a 5K.

• Physical Activity: Historically, and even compared to wild chimpanzees, humans are more physically active.

These unique human traits are all energetically costly, leading to the question of where this "extra energy" comes from.

Early hypotheses, like the "expensive tissue hypothesis" by Aiello and Wheeler (1995), suggested that to evolve a large brain, humans reduced the size and energetic cost of their gut, possibly due to eating more digestible meat and cooked food. However, this hypothesis didn't account for other expensive traits like longer lifespans or more babies.

Research using the doubly labeled water technique has shown that humans have a higher total energy expenditure compared to other great apes, even when controlling for body size. This means human metabolic rates are simply faster, churning through calories about 20% more than chimpanzees and bonobos.

• Body Size and Kleiber's Law: Metabolic rate generally increases with body size, but not in a one-to-one linear fashion. Instead, it follows a power law (Kleiber's law), where larger animals burn energy with an economy of scale. Therefore, accounting for body size is crucial when comparing metabolic rates across species.

• Fat-Free Mass: Fat-free mass (body mass minus fat) is a better measure for metabolic comparisons because fat is metabolically "quiet".

• Human Fatness: Humans are not only the highest-energy ape but also the "fattest ape," carrying significantly more body fat (15-25% for healthy males, 20-30% for females) compared to other apes (10% or less, even in zoos). Earlier studies focusing only on total body mass for BMR comparisons were misleading because they didn't account for this higher human fat percentage. When fat-free mass is considered, humans also have a higher basal metabolic rate compared to other apes.

• Evolutionary Explanation: This increased energy availability in humans is linked to the evolution of hunting and gathering, which began around 2.5 million years ago with the genus Homo. This mixed foraging strategy, involving both plant and animal foods, allows access to higher energy density foods (meat) and more reliable, lower-risk foods (plants). Crucially, the sharing of food within groups is what provides the metabolic boost, maximizing the benefits of both types of food acquisition. Cooking also increased the energy extracted per bite.

• Metabolic Adaptations: The shift to hunting and gathering is correlated with anatomical changes, including smaller teeth (less chewing needed for less fibrous food), a slightly smaller gut (especially the large intestine), and a more external nose (aids in water conservation, as human foods are drier and activity is higher in warmer climates). Humans also have an exceptionally acidic stomach pH, similar to scavengers like vultures, which suggests an adaptation for processing potentially rancid or bacteria-laden meat, a common practice among traditional human groups.

Energy Expenditure in Present-Day Human Populations

A large study leveraging the doubly labeled water database, which includes over 10,000 measurements from diverse populations worldwide (hunter-gatherers, pastoralists, farmers, and people in various economic contexts), investigated how energy expenditure varies across human lifestyles.

• Body Size and Economic Development: More economically developed countries tend to have taller, heavier populations with higher average BMIs and more body fat. Consequently, people in more developed countries, on average, burn more total calories per day largely because they are bigger.

• Lack of Lifestyle Effect on TEE: When controlling for body size, the study found no clear evidence of lifestyle effects on total energy expenditure across different human populations. For instance, despite being significantly more physically active than Western adults, Hadza hunter-gatherers burn the same number of calories per day as Americans or Europeans when body size is accounted for.

• Basal Metabolic Rate Adjustments: While the overall effect is small, a slight difference in BMR was observed: people in less developed countries tend to have slightly higher BMRs, possibly due to a higher pathogen load requiring more immune system activity. The immune system is metabolically expensive, and physical activity can tamp down background inflammation and stress reactivity (which are also metabolically costly), potentially freeing up energy for activity.

• Implications for Obesity: These findings suggest that differences in energy expenditure explain only a small fraction (at most one-tenth) of global obesity differences. Instead, energy intake (diet) is the primary driver of obesity. Populations with the highest body fat percentages consume the most ultra-processed foods, which are engineered for hyper-palatability, encouraging overconsumption despite satiety signals. While exercise is crucial for health, it is a poor tool for direct weight loss because the body tends to adjust its energy expenditure.

Obesity is a complex health issue influenced by a combination of dietary patterns, physical activity, evolutionary predispositions, and genetic factors. While the traditional, simplified view often attributes obesity solely to eating too much and moving too little, research provides a more nuanced understanding, emphasizing the primary role of diet.

Here's a breakdown of the causes of obesity based on the provided sources:

• Critique of the "Eat Less, Move More" Model
  
  

  • The common public health guideline often frames obesity as a 50-50 problem of diet and activity. However, exercise alone is a poor tool for preventing or reversing obesity. While crucial for overall health, increased physical activity doesn't necessarily lead to significant weight loss.

  • Studies, including those on Hadza hunter-gatherers, reveal that despite being much more physically active than Western adults, their total energy expenditure (TEE) is comparable. This suggests that the human body can adjust its energy expenditure in other areas (e.g., basal metabolic rate, immune function, stress responses, reproductive hormones) to compensate for increased activity. Essentially, if more calories are burned through physical activity, fewer are spent on other background physiological processes, leading to a relatively stable TEE.

• Primary Role of Dietary Intake
  
  

  • Caloric Balance: All calories stored as body fat must have been consumed and not burned. Therefore, body weight is fundamentally a balance between calories consumed and calories expended. Since exercise has a limited impact on increasing overall caloric expenditure, dietary energy is the main driver of obesity.

  • Food Type and Palatability: While a calorie is a calorie once absorbed, the type of food consumed significantly influences how much you eat. Foods with higher fiber and protein content tend to promote satiety, making it easier to consume fewer calories without feeling miserable.

  • Ultra-Processed Foods (UPFs): These foods are a significant contributor to overeating and obesity.

    • Definition: UPFs are generally defined by the number and combination of ingredients and extensive processing steps, often coming in colorful packages with long ingredient lists.

    • Impact: They are often "hyper-palatable", meaning they taste so good that they can override satiety signals, making individuals more likely to keep eating even after consuming sufficient calories. The exact mechanisms are still being researched, but it's thought to be related to how these foods affect the brain's reward centers.

    • Correlation with Obesity: Research indicates a strong correlation between higher consumption of ultra-processed foods and higher body fat percentages in populations.

• Evolutionary Predisposition
  
  

  • Humans are described as the "fattest ape," naturally carrying a higher percentage of body fat (15-30% for healthy adults) compared to other apes (10% or less). This evolved predisposition to deposit fat means our "normal" level of body fat is higher than that of our primate relatives.

  • This inherent tendency, combined with the abundance of easily accessible, hyper-palatable foods in modern environments, contributes to the current obesity epidemic.

• Genetic Factors
  
  

  • Individuals enter the world with a genetic predisposition that can make them more or less likely to struggle with weight.

  • Evidence suggests that these genetic factors primarily affect the brain's wiring related to hunger, satiety, and reward centers. This can influence an individual's drive to eat and their response to food cues. The success of new weight-loss drugs like GLP-1 and GIP drugs, which target these brain pathways, further supports this idea.

• Economic Development
  
  

  • On average, people in more economically developed countries tend to be taller and heavier, with higher BMIs and more body fat.

  • While individuals in developed countries may be more sedentary, their total energy expenditure is generally higher than in less developed countries, primarily because they are larger in body size.

  • The variability in energy expenditure across the globe explains only a small fraction (around 10%) of the differences in obesity between populations; the remaining differences are attributed to energy intake and diet. This indicates that the environment of readily available, often ultra-processed food plays a more significant role than differences in activity levels or inherent metabolic rates between populations.

In summary, while physical activity is vital for health, dietary intake, particularly the increased consumption of hyper-palatable ultra-processed foods, is identified as the primary driver of the obesity epidemic. This is compounded by an evolutionary predisposition for humans to carry higher body fat, and individual genetic variations influencing hunger and reward pathways in the brain.

Metabolic adaptations refer to the evolutionary changes in an organism's energy expenditure and utilization that enable it to survive and thrive in its environment. Humans have undergone significant metabolic adaptations that set us apart from other primates, largely driven by shifts in our diet and lifestyle.

Here's a discussion of key metabolic adaptations in human evolution:

• The "Human Paradox" and Increased Energy Expenditure: Humans exhibit a "paradox" in life history, possessing several energetically expensive traits simultaneously, such as long lifespans, large brains, frequent reproduction with bigger babies, and higher physical activity levels compared to other great apes. This challenges the typical evolutionary trade-offs where energy allocated to one trait limits others. Research indicates that humans burn significantly more energy per day than other great apes, even when controlling for body size. Our metabolic rates are approximately 20% faster than those of chimpanzees and bonobos, and even higher compared to gorillas and orangutans. This higher total energy expenditure (TEE) and higher basal metabolic rate (BMR) provide the physiological basis for affording these energetically costly traits.
  
  

• Dietary Shift and Gastrointestinal Adaptations:
  
  

  • Hunting and Gathering: A major metabolic shift occurred approximately 2.5 million years ago with the origin of the genus Homo, marked by the adoption of a hunting and gathering strategy. This involved not just hunting or gathering, but a combined approach with sharing of resources, offering the energy benefits of both carnivory (meat) and herbivory (plants). Before this, early hominins like Australopithecus afarensis (e.g., Lucy) primarily ate plants for millions of years.

  • Smaller Gut and Teeth: This dietary shift, along with the advent of cooking, which increases available energy per bite and aids digestion, led to anatomical and metabolic adaptations. Humans evolved a smaller digestive tract, particularly the large intestine, and smaller cheek teeth (molars). This is consistent with the "expensive tissue hypothesis," suggesting that consuming easier-to-digest, energy-dense foods reduced the metabolic demands of the gut, freeing up energy for other organs.

  • Bigger Brains: The energy savings from a reduced gut size are hypothesized to have directly contributed to the evolution of our large, energetically expensive brains, which burn about 300 kilocalories daily (the equivalent of running a 5K every day).

• Increased Body Fat: Humans are uniquely the "fattest ape," with healthy adults typically carrying 15-30% body fat, significantly more than other apes (10% or less, even in captivity). This evolved predisposition to store fat provides a crucial energy reserve to support our high metabolic demands and energetically expensive traits. This higher fat mass initially made it seem as though human metabolic rates were not that different from other apes when comparing total body mass, but accounting for fat-free mass reveals the true difference.
  
  

• Water Conservation and External Nose: The evolution of an external nose in early Homo is linked to water conservation. Humans are unique among apes in needing to drink water daily, consuming about one-third less water than expected for their body size compared to other apes. This adaptation became vital as humans began eating drier, often cooked foods and became more physically active in hotter, less humid climates, unlike forest-dwelling apes who obtain most of their water from plants.
  
  

• Low Stomach pH: Humans possess an incredibly acidic stomach pH, similar to scavengers like vultures, but significantly lower than that of carnivores or herbivores. This adaptation is believed to be crucial for killing bacteria in consumed food, suggesting that early humans likely consumed meat that was not always fresh or pristine. Historical ethnographic accounts support that people across the globe, including hunter-gatherer populations, have eaten rancid meat.
  
  

• Metabolic Flexibility and Ketosis: While humans are adaptable, the idea that humans are naturally in a state of ketosis is not supported by evidence from traditional populations. Even high-meat, low-carb Arctic groups like the Inuit do not consistently go into ketosis; in fact, some have adaptations to prevent ketosis. Ketosis is observed in apes when starving, not as a standard state with high-meat diets.
  
  

• Speed of Adaptation (Lactose Tolerance): Metabolic adaptations can occur relatively quickly. The ability to digest milk as an adult (lactose tolerance) evolved independently in different populations within a few thousand years after the development of dairy farming, demonstrating that strong selective pressures can lead to rapid genetic adaptations related to diet. Furthermore, the body can adapt through non-genetic means, such as changes in the microbiome or enzyme production.
  
  

• Modern Human Energy Expenditure Adjustment: Despite drastic lifestyle changes, including reduced physical activity in industrialized societies, overall total energy expenditure in modern humans, when body size is accounted for, is comparable to that of physically active hunter-gatherer populations like the Hadza. This suggests a background adjustment where increased energy expenditure from physical activity is offset by a reduction in other metabolically expensive background processes. These include lower immune system activity (reduced inflammation), reduced stress reactivity (lower cortisol and epinephrine responses), and decreased reproductive hormone levels in more active individuals. This adaptive capacity means that merely increasing exercise does not necessarily lead to a proportional increase in total calories burned or significant weight loss, as the body adjusts its energy allocation. This inherent adjustment of the body's energy budget plays a significant role in understanding why exercise alone is often ineffective for reversing obesity.
  
  

TRANSCRIPT

Whether food, drugs, or ideas, what you consume influences who you be. Come on the mind and matter podcast. We learned together from the best scientists and thinkers alive today about how your mind body reacts to what you feed it. Before starting mind and matter, I spent 10 years in academia doing scientific research. I got a PhD in neuroscience where I focused on neuroendocrinology and the neurobiology of behavior. And before that, I specialized in molecular, developmental, and evolutionary genetics. I use my scientific background to help parse and translate the information that guests share on the podcast. In addition to the podcast, I write long form written content inspired by the show, where I integrate what I've learned across episodes. I also have a free weekly newsletter where I provide you with upcoming guests, share links, and provide commentary on scientific studies and research that I'm reading and more. Visit mind and matter.substack.com to find all of my content. Thank you very much for joining me. Glad to be here.

You want to just start off by telling everyone a little bit about who you are and what you do?

Sure. Hold on. Let me just make sure this is not crazy. Uh, good. So, I can't do self view while I'm doing this because otherwise it's like a weird

Yeah.

Pablovian thing. I can't not look at myself. My shiny head.

You're

Hi, I'm Herman. Oh,

go ahead. I was You're centered. You're fine.

Good. Uh, I'm Herman Poner. I'm a professor of evolutionary anthropology and global health at Duke University. and the author of a new book called Adaptable.

Adaptable. And so what's the basic premise of the book?

Yeah. So Adaptable is all about how your body works and why you ought to care. Uh because so many of you know the big questions we wrestle with in society today, whether it's race or gender or IQ or when does life begin or what should I eat for dinner? Um all of these big topics that we are wrestling with uh fundamentally rest on how our how we understand our bodies and how you know, we think they work um and how they work differently. And so to have some fluency in that and get into some of those discussions, that's the the focus of the book.

Yeah. I think a lot of what we'll talk about today is how different bodies work differently, different human bodies within the species homo sapiens, but how that's also changed over time and then how we compare to other animals like other primates. And you've written a lot about

lots of different topics um on these different subjects. What what do you consider yourself academically as your back are mostly in anthropology. Were you a primatologist? What's sort of your your academic history here?

Sure. So, um, undergraduate and graduate degrees are all in anthropology in sort of with the focus on biological anthropology. Uh, but I would consider myself a physiologist, basically a physiologist who works on humans. Um, and what that means is, you know, in today's academia, um, in the US anyway, if you work on humans, you're either in a medical program or in an anthropology program because biology departments generally don't have uh human biology researchers.

And you've written a lot about primate evolution, how humans compared to that. I actually want to start out on a paper uh that you wrote, you know, a number of years ago now, but it's basically a comparison of metabolism between humans and our closest most closely related living primate cousins, chimps, gorillas, and so forth. And the first sentence in that paper says, "Variation in life history reflects differences in energy expenditure. Can you break that down for us? What is life history? What is energy expenditure and what does that statement mean?

Yeah. So life history is the pace at which an organism any organism uh develops, grows up um and then reproduces because that's the sort the evolutionary goal of any organism and then grows old and eventually dies. And so that kind of the pace of life is life history and um you know it's not it's something that evolves, right? So you can have shorter development periods or longer development periods. Uh life expecties of a different of different species are not just sort of you know random they they evolve as well. So um so to to grow up takes energy to reproduce takes energy to keep your body from breaking down as you grow older all of that takes energy. And so we can think about life history and energy expenditure as really tightly related phenomena.

Yeah. And when we think about that we immediately notice that there's some pretty clear trade-offs. that we tend to see, you know, across animals and organisms. You know, there's only so much energy an animal is going to be able to obtain and create and utilize

um depending on, you know, what it's doing. And, you know, if you put more energy into one thing, that's going to leave less in your energy budget to do other things. And so, in general, when we think about these trade-offs, we might notice that, okay, if if a species allocates a lot to reproduction, producing a lot of babies early on in life, there's le less left over to do other things. And so, those species tend to say live less long. than other species. And so, you know, different different life histories reflect those trade-offs. But then we come to this what you call the human paradox, which is, okay, we're a naturally fertile population. At least we were until pretty recently. Uh we have a lot of babies compared to other creatures like us, like other primates. They're bigger. They uh you know, and there's more of them, so that's more energy. So then you would think, oh, there's less energy left over to say have a big long life. And yet that's not what we see in humans. We we are fertile compared to other primates. Our babies are bigger. They have extended developmental periods, but we also live a long time. So, so what is this human paradox here?

Yeah. Well, that's just it. You know, you some somehow rather than seeing trade-offs when we look at humans, uh we're seeing that, you know, not only do we have long lives, which must take energy. We also have lots of babies and they're big compared to other apes. Uh so that must take energy. And then, you know, you might think, well, maybe we're saving energy in other ways, but actually we also have big brains. Right. Brains are incredibly expensive. Um the human brain, you know, burns 300 kilo calories a day, uh which is the equivalent of running like a 5K, um every day. And um you know, we also are more physically active, at least, you know, until very recently, um than other apes are. So yeah, there there doesn't seem to be anywhere that we're saving energy. And instead, it seems like all of the kind of traits that make us different from other apes uh and special are energetically expensive all of them.

So, so it's not obvious at first blush where this trade-off is being spoken for. We're not we don't seem to be taking the energy from one part of our life history and putting it somewhere else. So, it's almost as if there's extra energy here somehow. You know, before we get to sort of the work that you've done and what your answer is today, what have some of the traditional explanations or hypothesis been around how you might start to explain this?

Sure. So, the classic um idea, and this actually goes back to the 1800s. This is sort of an early post Darwin idea. Um the first uh I mean even kind of pre-Darwin like Gerta talks about this but anyway um not with humans specifically but the idea that there are these trade-offs and so um the first anthropology human evolution kind of version of this comes out in the 1800s but it really becomes uh kind of canon with a really important paper in 1995 uh by Leslie uh uh Leslie Ielo and um Peter Wheeler. Uh and it's this idea that to grow a big brain, to evolve a big brain, I should say, humans have had to evolve a smaller gut. And so your gut, you know, different organs are sort of different in how many calories they burn per minute. Um some energy, some organs are really expensive. We we talk about some organs are less. So uh fat, for example, burns hardly any energy at all. Um skin is pretty quiet, but brains are really active. and really energetically expensive and so are your your digestive tract and liver. And so the idea in this Iel and Wheeler paper 1995 uh they say well humans have evolved a smaller gut um probably because we eat meat and which is easier to digest and more energy dense um and now more recently because we cook our food as well. So that both of these things have shrunk how much our work our need our digestive tracts need to do and that has freed energy up for something else. And in our case, you wouldn't expect this in every species case, but in our case, those extra calories, the the the, you know, selection evolution has favored those extra calories to go to big brains.

Mhm.

Uh and so for a long time, um I guess now for 30 years, right, 30 years ago, uh that became just canon, right? That was accepted as the reason and and the why and how that humans have evolved these expensive traits.

So the basic idea is okay, we've got these big brains to explain and we've got this human paradox to explain. So the basic idea here is to have a bigger more expensive brain you got to take that energy from somewhere else and perhaps humans took it away from organs in the GI tract. And so you basically have a let's just call it a smaller gut overall. It's using less energy and then that energy is taken and used to create a big brain. That's the idea.

That's the idea. And importantly, you know, they didn't talk about the fact that we have bigger babies and more of them. They didn't talk about the lifespan issue, right, in that paper. That wasn't the focus of the paper. That's not a that's not a

a cut on that paper, but it's they just didn't focus on those things, which we know are also expensive things. So, even that paper didn't explain everything. Um, but it's it was a first crack at at this question about how do we do this? How do we have an expensive brain for example?

Yeah. Yeah. And so, I mean, to answer this, um, you know, at the end of the day, uh, eventually people can just look at these things, you know, how anatomically and physiologically what what do the energetics of these different organs look like how how big are they so to speak literally and you know in other ways in terms of how energy intensive they are.

Let's build uh some vocabulary for people because one one of the things you've done in your research is you've looked at things like basil metabolic rate total energy expenditure and so forth across species. So

we've got this human paradox to explain. We've got these long lives. We got these big brains. Um we have to explain you know where where the energy is coming from this. Are we taking it away from certain organs? Are we do we change something about our metabolism and how it's working in other ways.

Let's start with total energy expenditure. What is that and what are its major components?

Right? So, total energy expenditure is kind of what it sounds like. It's all the calories that your body burns over a 24-hour period. And that includes everything your body needs to do from the kind of background, you know, maintenance kind of physiological tasks like an immune system and your heartbeat and keeping your nervous system going and every everything uh to the stuff that we kind of notice like moving around. found um you know staying warm if you're cold, shivering, that kind of thing. Any anything you do digesting your food, all of it is included in total energy expenditure. Now um more than half of that energy that you burn every day is spent on just the background basic stuff that your body does to keep you alive, stuff that you don't notice, stuff that you're doing while you're sleeping, for example. Uh and we call that lowest level of of just maintenance energy expenditure. We call that your basil metabolic rate. Um, and it it has different terms and so people will see things like resting metabolic rate, basil metabolic rate, basil energy expenditure. Um, so it does get a little confusing. Uh, and there sort of different flavors of of criteria that people use to sort of make these sort of fine distinctions, but we don't need to worry about that for this discussion. We we'll just call it all basil metabolic rate.

Yeah. How much it costs to run your body when you're not really doing much.

Exactly. Exactly. Um, and then, you know, so there that's that's something like 60% of your energy expenditure, even if you're an active person, even if you exercise most days.

Yeah.

You know, over half of your energy is still being spent on stuff that's not movement, that's not exercise.

Um, another 10% or so of your energy expenditure is is burned to digest your food, right? Because you've got a breakdown of the the bites of food you take have to get broken down into their constituent parts and absorbed. And then those nutrients have to get trafficked into your cells. All that takes energy. So about 10% of your daily calories burned goes to that. Um, and then the rest is is a little complicated. Well, we can call that active, sorry, we can call it activity energy expenditure. That's often what it's called. But it's important to recognize that that leftover chunk, it's not basil metabolic rate. It's not digestion. A lot of it is movement. Um, but it includes other stuff, too. So, right now, talking to you, for example, I'm not really moving,

right?

But my body's on alert,

right? My nervous system tone is a little bit higher than it would be if I was sleeping surely

right

and so my energy expenditure right now talking to you is higher than it would be if I was sleeping higher than my basil metabolic rate and if I just do a simple subtraction exercise to get activity energy expenditure if I just take my total energy expenditure I subtract basil metabolic rate I subtract digestion whatever I have left I call activity well what we're doing right now is going to get lumped into that activity

right so activity includes overt movement like if I go play basketball or just walk around but it also just includes uh being alert aware engaged. Uh this is where you know famously you know chess players when they're competing they burn an incredible amount of calories. So when you are doing something in that sense whether it's overtly physical or not that's the active component.

Exactly. Exactly. And and also I should say things like staying if you're outdoors shivering right we you're not allowed to be shivering while we measure your basil metabolic rate. So something like shivering it's never included in BMR. Um yeah if you're scared uh you know the sort of fluctuation that this kind of cadian rhythm in your organ activity isn't really captured in this because we always measure basil metabolic rate in the mornings when you're at your most quiet.

So, you know, there's a lot that goes into activity, energy expenditure that isn't just physically walking around playing basketball, that kind of thing.

Okay, so we've got ba basil metabolic rate. We've got active energy expenditure, which includes overt movement and just other forms of engagement. And we've got total energy expenditure, which is everything.

When we think about total energy expenditure and its component piece, is now we can just simply ask the question uh how do humans compare to primates like gorillas and bonobos and things like that. Let's talk about that next and maybe to do that you should talk about how you guys actually measure these things in in species.

Yeah. So um you would think you could just go and measure it, right? Uh and and until the 1980s there actually wasn't a way to just go and measure it. Uh to measure total energy expenditure you need this technique called um doubly labeled water which is an isotope tracking technique. You drink some topically enriched water and we measure those isotopes of hydrogen and oxygen as they flush out of your body over a week or two weeks and from the rates at which you flush out the hydrogen versus the oxygen isotope we can calculate how much carbon dioxide your body makes and therefore how many calories you burn it's a very precise good way to do it in fact it's the only way to measure total daily energy expenditures outside of a laboratory setting

um and so there was no way to do total energy expenditures you know for apes for sure and even really to do it well for humans until the 80s when this technique finally got good enough for that.

So, it sounds like by allowing animals to drink this doubly labeled water, it's got a specific composition that has to do with the isotopes that you can find in water. I don't think we need to dig into the the hardcore details there, but basically what you're saying is you can measure total energy expenditure, but still allow the organism to basically go about its day and not just be hooked up to a bunch of contraptions in a lab.

Precisely. You're not locked in a room. You're not don't have a mask on. You're just doing it's just normal daily life. We just need to get a couple of your urine samples over the course of the sort of, you know, a week or two weeks. Exactly.

Okay. So, let's let's get into some of the the topline results here. So, when you do these types of experiments across primate species, what are the species you guys looked at and what did you what did you see? What was total energy expenditure like in humans compared to other species?

Right. So, we looked at all of the great ape uh genuses. So, we did orangutans, gorillas, uh chimpanzees, and bonobos. They're the same genus, but they're different species.

And these are all captive. They're all captive. That's right. Um and so, you know, these are all like good zoos or sanctuaries where they can move around as much as they want. They're not like, you know, in a medical cage or something like that. They're they're out free ranging, but they're they are in a zoo. That's right. So, they're captive.

Uh we use this technique. Um nobody had ever measured total energy expenditures in apes before, so this was a first for that. Um and yeah, so we had at the end of the day, it's took years to do and was with my good collaborator Steve Ross at Lincoln Park Zoo. and Mary Brown, some others. Um, we finally had total energy expenditures, calories burned per day for all of the great apes, plus of course humans. There's lots of human data out there that we were able to use.

So, so what did you see?

Yeah. So, um, when you compare how many calories we burned for how big we are, right? Because you have to account for body size and all these analyses,

you find that humans are burning 20% more energy every day. Our our metabolic rates are just faster. We're burning we're churning through calories at about 20% more. per day than chimpanzees and bonobos, which are the most closely related group to us. And then we're also burning even more energy compared to gorillas. Gorillas are a bit lower than chimps and bonobos. And then orangutans are their own really interesting story. Orangutans seem to be one of the lowest metabolic rates ever measured uh for any any placental mammal. So marsupials are kind of strange. That's a fun conversation for maybe for another day.

But if you look at non-marupial mammals, uh Uh, orangutans are the lowest ever measured except for sloths and pandas. So really low metabolic rates in orangutans. But humans the the human story is we have we're the fastest metabolic rate uh we're the high energy ape compared to all of our other ape relatives.

And you said so we have high total energy expenditure compared to other primates controlling for body size. Maybe we should briefly mention what is the when you just look across the animal kingdom. What's the general relationship between metabolic rate and body size and why is that important to consider here?

Yeah. So um you know where does your metabolic rate come or more why do you burn calories at all? Well, you all of your cells are burning energy all the time just to do their their daily functions. Um, and so, you know, the more cells uh there, the more energy you're going to burn. Um, so, you know, mice don't burn as many calories every day as an elephant does, right? Just because a mouse is tiny, doesn't have many cells compared to an elephant, elephant's made up of many more cells and therefore just burns more calories just just by virtue of being bigger.

Mhm.

Uh, And so there's a it's an interesting sort of relationship actually. It's not one to one. So you might think that let's just use some toy numbers. If a 1 kilogram animal burns 100 calories a day, you might expect that a 10 kg animal would burn a,000 calories a day, 10 times more. But that's not actually what you see.

There's like an economy of scale. So yeah,

the the animal that's 10 times bigger

will only burn like seven times more energy,

right? So somehow they're kind of saving energy there. There's like an economy of being bigger.

Um, and it's so it follows a power law that's very well known since the 30s, 1930s,

um, called Clberers's law. So that the total energy you burn every day increases with metabolic rate to the 75 power. Yeah,

we do the math that we want to anyway. But so we have to control for body size in any analysis we do because bonobos and chimpanzees are much smaller than your typical human. Gorillas, male gorillas are much bigger. Um, orangutans are, you know, can be kind of the same size or bigger or smaller. So you have to control for body size in any analysis of energy expenditure

and you have to do it in a smart way because that power law kind of curve relationship

not one to one.

Exactly.

Yeah. This is and this this is very consequential, right? Like if you were to just naively scale things one to one and say dose an animal with a drug and say ah it's 10 times bigger. Let's give it 10x the dose. That's going to become very consequential and even life-threatening.

Oh 100%. That's exactly right. So there's all sorts of reasons that we have to understand this relationship. Um it's Also why by the way um you know if you ever see somebody looking at the kilo calories per kilogram right you see people try trying to kind of account for body size by just dividing your body mass by how many calories you're burning

you ever see that simple ratio that should be a red flag because that ratio assumes a 1:1 relationship

and when there isn't a one one relationship you can kind of get funny answers so

right FYI

yeah

buyer beware

okay so so controlling for body size humans have some something like 20% higher

total energy expenditure than than we might expect otherwise compared to other apes.

Compared to other apes. That's right. That's right. So, you know there So, it was awesome because we finally had an explanation for how we how can we do all these expensive things.

More energy.

More energy. That's that's the how, right? Doesn't necessarily tell us the why. That's an interesting evolutionary story. But finally, we had an actual physiological explanation for how because we didn't have that until this work came out.

And so, uh, let's dig into this a little bit more. One of the other things you look at is the relationship between free fat mass and total energy expenditure across ape species. What can you tell us there?

Yeah, so fat free mass is kind of just what it sounds like. It's the how much body mass you have minus your fat. And the reason we do that, we we look at that measure is that like we said before, different organs, different tissues are, you know, don't they don't all burn the same number of calories per per day.

Uh fat is really quiet. It doesn't do much metabolic work. And so um if we just look at your total body weight. That's not the best kind of measure of your your metabolic size, if you want to think about it that way. Your best measure of size in these metabolic comparisons is fat- free mass.

And that would that would be really important if if the proportion of body fat differed between species, I would imagine.

Yes. And it does, by the way. And so early work looking at just basil metabolic rate, that resting metabolic rate measure in humans and other apes had found kind of misleadingly that there wasn't really a between humans and other apes. And that's because humans actually carry a lot of fat. Uh we're not just the highest energy ape, we're also the fattest ape, which is kind of fun to think about. Um and so, you know, a 50 kg human, 110 pounds, was had the same basil metabolic rate as a 50 kilogram chimpanzee, more or less. And so people said, "Oh, well, look at that. It's, you know, humans are no different than other apes metabolically." Not true because humans carry a lot more fat. And so actually you if we had exactly the same metabolic profile, our tissues were all burning the same number of calories as as as each other, humans should have a lower metabolic rate at that 50 kilogram body size,

right? How much more fat do we have? And and where is that fat mostly? Is there a pattern there?

Yeah. Uh well, so humans, you know, a healthy human male adult could carry might carry between 15 and 25% body fat, let's say. Um you know, more is usually okay. A little bit more too much more and you become you have obesity issues. Uh less than 15 or certainly less than 10% and you're a little bit too lean typically people think. Um female humans you know can carry a bit more fat. Maybe 20 to 30% would be normal for a female human maybe a bit over 30. Uh for an ape even in a zoo uh a pretty sedentary ape they carry 10% or less body fat. They're actually really lean.

Wow.

You go to a zoo and see them sitting there these big pot bellies, but that's because their digestive systems are so big. They're not actually fat.

Okay. That's not visceral fat. That's uh that's just a different gut.

Yeah. Exactly.

Interesting. So So a fat chimpanzeee would be like 10% body uh body fat.

Yeah. Yeah. You would be Yeah. And um it's they're really lean. Um orangutans are interesting. They're they're a bit fatter than gorillas and chimps and bonobos. So they seem to be kind of more humanlike in that regard. Uh but yeah,

quite a bit less. I mean, I'm looking at the chart. It's still quite a bit less than humans.

That's right. That's it. Yeah.

Okay. So, we've got higher fat mass. That fooled us for a while into thinking our metabolic rate didn't really stick out much, but it turns out when you measure this with doubly labeled water, which allows you a precise measurement of total energy expenditure. Humans have more total daily energy expenditure than other apes controlling for body size. So, basically, there's there's more energy for us to use to do stuff. And that must be related to this apparent paradox where, you know, how come there's no trade-off between say longity and reproduction. Well, a lot of it could be due to the fact that we just have more energy at our disposal.

That's right. Yeah. And then, you know, the next kind of question to ask from an evolution evolutionary perspective is, well, why don't these other apes just ramp up their metabolic rates,

right? If having more energy is so good, why doesn't everybody do it? Um, and the answer is, well, it's it's also a cost, right? So, you have all this energy available to do all this cool energy, you know, evolutionary stuff, big brains, more babies, but you have to feed that machine every day,

right? And so you need to have more energy available to you if you want to ramp your metabolic rate up like that evolutionarily. Um, and so, you know, just among humans and the other apes, there's there's two really fun stories there. Uh, there's the human story, which is how do we get extra energy? And the answer is hunting and gathering and sharing and the sort of mixed portfolio that we have. Some of us hunt, some of us gather. You have the benefits of being a carnivore and the benefits of being a planteater combined. I mean, it's it's a really great Y that's that is why we're such a successful species.

Yeah. So there's division of labor there. You can get a higher diversity of foods in different contexts. I would imagine this could be where cooking comes in to some extent.

Yeah. Cooking helps as well. It's going to increase how much energy per bite that you're able to get out of out of your food. Um but that's right. So you know plant eaters uh they're going after a lowrisk, lowreward food, right?

Famously, right? Like chimps and chimps and gorillas I believe they kind of just like eat all day, right? They have to constantly be ingesting and chewing that plant matter.

Yeah, especially gorillas. Gorillas go after really low quality. That has a specific meaning in ecology. We just mean low energy leaves. Uh, you know, not too much fruit, although they will eat fruit if they can. Chimps focus more on fruit, but still also al eat leaves to kind of bulk out their diet,

but none of those have as much energy as, you know, as meat,

right? So, just right right out of the gate, there's just less energy to extract per unit time if you have that kind of ecological dietary focus.

Exactly. Now, on the other hand, if you go after just meat, well, now that's really risky because even the best hunters are going to come home empty-handed most days.

Mhm.

And so, you know, carnivores are playing a different strategy, but they also can't depend on those calories every day, right? And so, how do you maximize the benefits of both? Well, you have some of your group go and get plant foods, some of your group go and get these high energy animal foods, and you share it. And so, On days that the hunters come home empty-handed, that's okay. And on days that they come home with, you know, with a a kill, it's amazing. You have tons of calories and and protein and fat. So, um, you know, so it's that really just launched this set of of adaptations that we see in humans today.

What about basil metabolic rate? How does that vary between humans and apes?

Yeah, so we also have a higher basil metabolic rate. And you know, again, that was confusing with from data. from from kind of the 1960s, '7s, '80s because when you just looked at body mass, we didn't look that different. Um, and people hadn't sort of carefully and correctly accounted for body size differences. Um, and so when we that's another thing we did in this paper in 2016 was to to reassess the basil metabolic rate data. Uh, first of all to look at it with this kind of power law curve linear relationship in mind. Other papers earlier hadn't really done that. And secondly to make the distinction between um total body mass and fat free mass. And um when you take both of those issues into consideration, humans also have a higher basil metabolic rate, which you'd expect, right? It's not just it's it's it's kind of evident everywhere is faster metabolic rate.

Yeah. Yeah. Okay. So, higher basil metabolic rate for humans, higher total energy expenditure for humans. Uh another question that comes up here, especially, you know, we'll talk about this more as we talk about, you know, hunter gatherers and ancient or traditional populations versus

present- day populations, but what about um just ive energy expenditure especially in the context of moving around. Were hunter gatherers moving around all day uh as much as other apes?

Uh oh. I mean so I should point out that this human comparison to other apes we used humans in western industrialized contexts.

Yeah. Yeah.

Right. So you know obviously if you compare really physically active hunter gatherers to apes in zoos then the immediate response will be well that's not a fair comparison.

Got it. So you basically you basically looked at both sedentary humans and sedentary apes.

Exactly. Exactly. And if you look at like the number of steps that that people are getting and the apes are getting, um, it's pretty comparable. So, we wanted to make sure we were had an apples to apples comparison for that study.

Um, yeah.

Okay. So, so total energy expenditure is higher. Um, that's just what you measured. So, that's the observation. Yeah.

How do we start to think about, you know, we started to talk about this a little bit, but how do we start to think about how that's happening and why that's happening from an evolutionary perspective? Yeah. So, um, again, all of the human adaptations that kind of set us apart, our big brains, our long lives, which you have to invest in your body to maintain it, to live a long time.

Uh, we have more babies more often, everything that kind of makes us unique and different from other apes. It's it's energetically expensive. Um, and so that's where those calories are going. Um, and we're also more physically active during the day. Even a sedentary human And you know, even me here with a desk job at Duke University, um I mean, I like to exercise, but you know, a lot of days I'm just kind of hanging around, but even so, if I get 5,000 or 10,000 steps, that's pretty good compared to like a chimpanzeee in the wild. A chimpanzeee in the wild, they don't, you know, they go a couple kilometers a day. They climb a bit.

So, it's not like they're walking around foraging and climbing trees all day long.

No, they sit a lot. They rest a lot, digest a lot. Um Yeah, exactly. And so uh you write in this paper as well and we talked about it. So humans have more fat. Um we have this evolved predisposition to deposit fat whereas other homoids, other apes are relatively lean even in captivity as you pointed out where activity levels are are modest compared to in the wild.

What are some of the implications there for obesity? Does this sort of hint that we are just sort of naturally predisposed to get fat and uh that that could you know there's basically just a like a something built in to the human that predisposes us to to have high levels of atyposity.

Yeah, our normal level of body fat is just higher than other apes. And so we seem to to want to to build that. Um you know um if you look across the mammal world, there's different kind of ranges for what a normal amount of body fat is, right? So uh you know, famously Arctic species that have to live in the freezing cold have a lot of body fat to stay warm. Humans aren't like that. We're not saying that. But we do have more body fat. Our our normal amount of body fat is just more than most other primates and and certainly more than our our ape relatives.

That's right.

So So that's the way things are as they've been measured today. You compare humans to uh chimpanzees, bonobos, gorillas, ranging tanks that are around today. Now I want to talk about how we got there as a species, how that line, how our lineage transformed over time. Thinking about how diet changed on average, how metabolic adaptations um you know came into the picture over time. So When we think about human diet and the origins of not just homo sapiens but say the entire genus homo,

what what would you point us to here to start thinking about this? What are the major themes and how diet metabolism started to shift around say the origin of our own genus compared to

Yeah. So, uh the big change that really launches our genus and and this whole you know human experiment uh and and really makes us different than other apes is hunting and gathering. And so around 2 and a half million years ago um we start to see stone tools and other indicators of behaviors in fossil hominins. So hominins are are lineage um and um you know we start to see indicators that those ancestors are not just gathering plant foods like other apes do and not just you know maybe hunting occasionally like a chimpanzeee does but are actually hunting enough often enough that we see stone tools dedicated to that. We see cut marks on animal bones in these old 200 2.5 million year old archaeological sites.

Mhm.

Um and along with that we see these anatomical changes that we think are related to diet and metabolism. And so we see uh tooth size getting smaller. The m the cheek teeth, the mers that are doing the chewing

get smaller because presumably because the foods that they're eating don't take as much chewing. They're not as much as fibrous and planty.

Yeah. So gorillas presumably have really big mers.

They have big mers and they're really sharp and they're they're kind of very clear. plant eating mers. We don't see that happening here. And and I should say that before that so humans the human lineage homins split from the chimps and bonobos around six or seven million years ago.

Mhm.

And for the first four or five million years those we have lots of good fossils of of our ancestors from that that time. Um species like apherentis like Lucy the Lucy skeleton have you heard of that?

Those species are all clearly eating predominantly plants.

I see.

Right.

So the shift So there was a shift towards more animal-based foods and less plant, but it wasn't really happening that much shortly after the time we split from chimpanzees,

right? It didn't happen for four four million years or so.

Yeah.

It doesn't happen until um around two and a half million years ago with the origin of our genus, the genus Homo. Um and in fact, that's why you know that's why we see I think you know these anatomical changes that we call the genus. Why do we call these fossils a different genus? Why do we call them our genus? Well, because these anatomical changes in in brain size, which is getting a little bit bigger, tooth size, um they're associated with stone tools, and we think of ourselves as as the best toolmakers, not the only tool makers, but the best tool makers. Um that's those are the suite of changes that we say, okay, well, that's that's our genus now. And it's this break from earlier, more AP kind of ancestors.

And so, what um so so we started to talk about a little bit but the so the balance of animal and plant foods is changing the the food acquisition strategy is changing so hunting and gathering comes into the picture in hunting is probably you know really big there now we're getting more of those animal foods compared to plant plant foods relatively speaking compared to other apes this is correlated in time with anatomic changes it's correlated both with the brain getting bigger these changes in tooth size presumably other changes as well in terms of you know like our our limbs and our our you know, fingers and stuff that's tied into tool making, which sort of unlocks the ability to to hunt and gather in new ways. Um, any other major changes that are worth calling out there, either in anatomy or in I don't know what you'd call it, like uh implied metabolic changes.

Yeah. Well, there's there's two that are important. One is uh not really an anatomical change, but we know it's happening is sharing,

right? And so hunting and gathering don't work without sharing. Right. It's not the hunting or the gathering. It's the and that's what makes hunting and the gathering so good.

Got it.

Uh and and we see, you know, we see cut marks on bones of animals that are so big, there's no way that one hominin was eating that, right? They must have been being shared.

Uh and it's the sharing of the food that gives you this metabolic boost, right? Because again, if you're just a planteater, you don't get the advantages of the meat. If you're just a meat eater, you don't get the advantages of the plant. You have to have both.

So sharing is huge.

Yeah. So hunting and gathering, emphasis on the and. Yeah.

There's a relative shift towards animal foods and away from purely plant-based diets that other apes have. Um, but we're consuming both. The and is is very important. What does that maybe imply about changes that must have happened in what we might just call metabolic flexibility, the ability to handle both types of food um and not just focus on only plants like gorillas?

Yeah. So, our guts get a little smaller because we're not just eating this all pure fibrous diets anymore, fibery plant foods anymore. Um, but yeah, we're able to handle a whole range of foods and that is you can see that in our teeth, you can see that in our guts. Um,

and when you say the gut got smaller, do you mean like the length of the tract? What specifically does that mean?

Yeah, the the the tract gets a little bit smaller. Specifically, the large intestine gets a little bit smaller. That that's, you know, we can see that today. By the way, we don't have fossilized intestines, right? Uh, but, you know, based on kind of the shape of the rib cage and what we reconstruct to be the shape of the belly and that kind of stuff,

yeah,

it looks like that's all happening then. Not not all once right away, but like Seems like it's happening that way.

Okay. So these these shifts happen over time. Many of them don't happen right away after the split from chimpanzees. It takes a few million years. The origin of homo is defined based on a suite of anatomic changes we identify that are what we discussed bigger brains uh changes in mers some other things. And that's you know that must have come with you know differences not only in the sort of food search and strategy and social behavior stuff but in metabolism as well.

Yeah. Here's another fun one. Um this is related metabolism. Uh we start to see an external nose evolve

in early homo. Uh so you look at a you know the face of a of a chimp or a gorilla it's a very flatfaced you know there's there's no there's no nose right I'm a good example of this. Um but the bony part of the nose you can you know it preserves in the skull and so we can actually see that begin to develop in early homo. Uh what does it do? Well we know from these same doubly labeled water measurements that we use to get energy expenditures also. tell us how much water the body is going through every day.

And it turns out that humans are water conservers, right? We don't use as much water. We use about a third less than you'd expect for our body size compared to other apes. And so, um, that's interesting. And that is telling us that there's sort of a different a different game going on. Um, if you're eating just plant foods and you're hanging out in forests where it's warm and humid all the time and you're not really physically ive then conserving water isn't a big deal. Most apes get all the water they need every day just from the plant foods they eat because plants have so much water in them and they hang out in these like low activity humid forests all the time.

Humans can't play that game. Our foods are drier especially when we cook them and we are more physically active in hot climates and so we have to drink water. Right? Humans are the only w only ape that needs to drink water every day,

right? Yes, he can get by with a day or two. Sure. Yeah.

But a chimpanzeee or gorilla could go days, even weeks, and be fine without ever drinking uh, you know, open water.

They get all the water they need from the plants they eat.

And so an external nose, we think, is helping to conserve water because when you breathe out through your nose,

the water vapor in your breath, right? The way you fog up a mirror, that water vapor in your breath has a chance to recollect uh against the internal surfaces of your nose.

And so, you know, this isn't we're still working on this question, but it seems like this is an adaptation for conserving water. And we see the the results of that today when we look at how much water our bodies use compared to other apes. And so, the beginnings of that seem to happen with with Homo as well.

Yeah. So, we we our bodies want to hold on to water. We need to drink water every day. We also sweat a lot. So, like there's something going on where we're trying to recycle and recapture the water that we're we're losing. all the time.

Yeah, that's right. That's right. I should say, by the way, that there are as a some folks uh this will get you into troubles. This is a good thing to bring up.

Uh there's a a group of folks out there who are sure that humans evolved kind of in rivers and other freshwater sources. Yeah, this aquatic ape idea.

Um and you know, I I don't think there's a lot of support for it in general in the field because, you know, there's not any great evidence for it. That's a pretty remarkable claim to make. So, you need pretty remarkable evidence. Um and the um you know for me the the killer to that hypothesis is that we are conserving water, right? I mean why would our bodies be built to conserve water if we were literally chest deep in fresh water or even you know had access to to water all the time. Uh and so um I like it for I like that result for that fun reason.

Yeah. And so there's another observation I want to call out here and ask you about because this ties in some ideas I've always been intrigued about uh in the in the realm of paleo anthropology. So the genus homo originates we start evolving as homo and we have the suite of adaptations that we just talked about. It definitely came with a relative increase in meat and animal food.

Um and there's some debates out there that people have had about you know how much were we near carnivores? Were we omnivores that just ate more meat than other apes? And you know exactly what did that look like? Another related question is were we hunting and killing live animals or were we say stealing carcasses from other predators. And there's a really interesting observation I want to ask you about that might tie into that. So if you compare stomach pH across different types of animals, humans, and then just omnivores as a category, carnivores, herbivores, and scavengers, what do things look like there? And what do you think that is maybe telling us?

Yeah, so we don't have any data for apes, which is what we'd really like, but humans have incredibly low, very acidic

stomach uh acid. You know, our stomach environment is really acidic.

And it looks like, you know, we look like uh scavengers. We don't look like carnivores, by the way. Uh and we don't look like herbivores for sure, which have much more comparatively neutral stomachs.

Yeah. So herbivores have the highest pH, but then carnivores and omnivores, you know, it's lower, but not nearly as low as scavengers and humans.

Yeah, that's exactly right. So, um we look like vultures.

Yeah. And scavengers, are they mostly eating dead and and rancid meat? eat or are there also omnivorous scavengers?

Well, uh I mean it kind of depend. A lot of animals we we use these classifications and then you go out and watch the animal in the wild and it'll you know they'll they'll do things you don't expect. So I don't want to say never.

Uh but you know the reason that you have the reason that vultures have this suite of adaptations around scavenging is that's how they get most of their calories. That's a really important part of their of their daily calorie intake. Even if they're not doing it all the time, they do it enough that selection, you know, favor to make them good at it. And so I think you can say the same about us whether we were eating rotten meat all the time that it really mattered.

Yeah. So for some period of time that was probably happening to some degree but it's really hard to pin that down precisely I imagine

I suppose but you know there a great paper just came out looking at this in uh you know ethnographically a series of papers by this guy John Spithth and he's an anthropologist in Michigan and he got very interested in this question about how much meat is being eaten in the Paleolithic, the stone age.

Yeah.

Um and and as a model for that, he looks at every account he can find of people eating meat in, you know, as as explorers are going around the world and and writing out what they see, you know, local groups doing, American Indians, South American groups, a whatever they are,

you know, he gets all these accounts from the 1500s, 1600s, all everything. Yeah.

And across the board,

these groups are all eating the most most rancid putrid.

Yeah. I mean,

I talked to Eugene Morren once on the podcast and I think I think he was talking about one of these accounts where early European explorers are interacting with uh Eskimos and basically he tells the story of like this this Eskimo that's camped out with these guys is so excited. One morning he brings this rotting just absolutely rancid seal carcass and they're all horrified and he's like got like this is this is gold. Like he was so excited.

Yeah. Yeah. They won't let him take it on the boat and he get so upset. Uh I love that account. And but you know, and it's not just the Arctic. This is everywhere in the world that people

So, okay, so this was a very general thing it seems to be.

Oh yeah. Yeah. Yeah. Yeah. So people eat rotten meat everywhere. Um so whether you know when that pH dropped in our stomachs when that change happened, I don't know. But my guess is, you know, I've had the chance to work with hunter gather groups here, uh hunter gather population in northern Tanzania, the Hodza. Um they're not really, you know, known for eating ranched meat, but they absolutely do and will uh meat that I would consider not okay.

Wow. Wow. So, so the interpretation here is that the low stomach pH is making maybe making rancid meat more tolerable because it's like a filter for bacteria or something.

That's right. It kill I mean the question about why do we have stomach pH at all? Low stomach pH at all. Part of it is it helps convert um an enzyme that helps you digest protein. But you know if that were the case then everybody who ate a lot of animal meat for protein would have carnivore like phes, but we don't. We have even lower. So why do you have such an even lower level of of pH and even more acidic stomach? I think the only obvious explanation is to kill bacteria.

So like a a predator like a cat, they're eating fresh meat that they just killed. So they don't that's why the pH is higher for them.

That's the interpretation you would have, I guess.

Yep. Yep.

Interesting. Okay. So So we we made this relative transition towards animal foods um to a fairly substantial degree, but humans were basically omnivorous to some extent everywhere you look for them. Um, we do have a smaller gut compared to other primates. We've got the slow stomach pH hunting and gathering developed so we can sort of take advantage of

all possible available foods more or less.

Um, and then you know we've got just higher total energy expenditure. So, so somehow all these things added up such that humans just have extra energy so to speak compared to other animals.

That's exactly right. Yeah. And you know that strategy wasn't available to other apes because they couldn't figure out hunting and gathering not that they're actively trying of course but you know if we sort of think about it like evolution like a game that strategy doesn't you know they don't they don't use that strategy doesn't occur to them whatever not available to them and so that's why we have this unique lineage and you know I want to get back so now I want to talk about um not the deep evolutionary history of our genus but after homo sapiens is around we become and up to the present day You know, there's hunter gatherers and traditional populations living all over the world in very different food environments. They're all hunting and gathering in to different degrees and diet is different all over the world.

Yeah.

So, you know, this starts to get us into questions around, you know, because today, you know, when you look at diet and

people get so excited and so tribal, you've got carnivore people and vegan people and then you've got, you know, everything in between and people are often talking about the human diet or what humans are supposed to eat. I want to talk a little bit now about how diet has varied around the world across what we'll just call traditional huntergather populations.

Leaving aside for a moment, you know, like us modern sedentary, you know, technological uh civilizational human beings. Can you talk a little bit about that? How say the mix of animal and plant foods has varied across traditional huntergather populations as a function of where they live?

Yeah. So, we have ethnographic accounts, people finding these communities and taking notes on what they see that go back to the early explorer days, the early European explorer days, 1500s, 1600s, then up to the sort of present day. Um, and we've got some these ethnographic accounts of, you know, over 200 uh populations worldwide. Many most of them are no longer really around anymore. They've been, you know, they're not intact cultures anymore, but um we got 260 different communities or more uh that were hunting and gathering. Maybe some had a little bit of farming, maybe some were doing a lot of fishing. You know, there's there's variation there. But we have 260 data points now to see how diet changes across the globe. And what you see is there's an incredible mix of how much animal food and how much plant food these populations are getting um across the globe. Like you expect, people in warmer climates are eating more plant foods because plants grow better in warm climates. And people who live closer to the, you know, the poles in more arctic environments are eating more animal foods because plants don't grow as well. there and there's more animal food available. Um, if you live near a river and can get get lots of fish all the time, guess what? Eat a lot of fish. Um, if you start farming a little bit and have, you know, some staple crops there, you eat more plants because that's what you're farming. So, it's it's a mix. Yeah.

Um, but even the pure hunter gatherers, you see a whole range of of foods.

Right. Right. Yeah. You've got this great graph in this paper I've referenced a lot and it's basically percent of diet from animals across all these traditional populations as a function of attitude and correct me if I'm wrong here but when I look at this basically if you get close to the equator people are eating 40 60 6040 mix of plants and animals so it's you know it's about 50/50 plus or minus some and then as you move away from the equator becomes more animal ccentric and you do have a variety of populations I don't know what the proportion is here but a solid chunk that are like you know 8020 or even close to mo almost all animal products that would be like the inuit or something like that

yeah that's right and so um a couple things to keep in mind there one is because because often that data point those, you know, 8020s or more of of animal foods get used to say, "Oh, look, we're supposed to be carnivores."

Mhm.

So, let me stop you right there and just say,

um, people haven't been in the Arctic full time until about 8,000 years ago.

That's that's less ancient than farming.

Right. Right. Right.

In terms of as a model of where we're we're from.

I see.

Um, unless you have recent Inuit an history. Uh that is not where you're from. Um yeah, so it's a it's it's a strange model. It's it's actually a stranger model of a of the past

in some ways than a farming population is.

So So the Inuit the Inuit are less old than farming.

That probably ties into So there is evidence of human carnivory in the last ice age, but that would again be a very very recent and short sort of time window that was sampled from. I want to ask you about sort of on this topic. So farming's, you know, 10 or 12,000 years old. Mhm.

I want to I want to get us give people a sense for the the speed of evolution and metabolic adaptation. So, I'll let you sort of direct where we go here, but if let's just say you're talking about farming, to what extent can we be adapted to a grain-based farming diet? If we've only had that for 10 or 12,000 years, how much adaptation can you get in that time? Can you completely adapt to a diet in that amount of time or does it take a 100,000 years? Say,

well, you're assuming that we didn't have those same nutrients in our diet before.

Mhm.

You know, why would it take a long time to why why would you have to adapt to a grainbased diet if you're eating starches in those foods if that's what you're adapting to? Well, there's starches in foods going back millions of years to when we're eating tubers,

right?

Um if you're trying to adapt to the specific nutrients, you know, micronutrients uh in a grain, then sure, that could take longer.

Um but we see adaptations to specific nutrients happening pretty quickly if there's enough pressure. So, for example, the ability to digest milk as an adult lactose tolerance.

Yeah.

That seems to evolve pretty quickly after the development of dairy farming. Yeah. Happens independently actually in Northern Europe and then in Northern Africa.

And that's that's like what a few thousand years of it sweeps through the population.

Yeah. Yeah. That's right. Um Oh, and by the way, a nice UK bio bank study recently. You don't have to have that genetic adaptation to eat and and enjoy dairy. People who without those genes still enjoy dairy and your body kind of figures out a way to digest it. So even if you didn't get, you know, let's

genetic based adaptation, you could still say have maybe it's a micro microbiome based adaptation or your predigest.

Yeah, that's right. Yeah. Your your pancreas and especially but the other parts of your digestive system make tons of enzymes. Whole, you know, bunches of different classes and types of enzymes that are good at all sorts of nutrients. Everything from protein to fat to carbs. Um your body is built to break down a bunch of nutrients that you might find noxious, right? And so there's no evidence that uh that there are these widespread inabilities to digest any of the nutrients that we find commonly in the human diet.

Yeah, it could just a lot of it could be context dependent metabolic changes, gene expression changes. I would imagine like if someone's lactose intolerant today, they go and drink a cup of milk tomorrow, they feel terrible, so they stop drinking it. I think what you're getting at is if they were to continue drinking it, their body might might in fact adapt to it.

It might. And even if it doesn't happen for that person, and by the way, I'm not telling anybody to go drink milk. If it makes you uncomfortable, don't do it. Fine. But that doesn't mean that your whole population,

right,

or that the human species,

right,

shouldn't be drinking milk.

Yeah.

Right. In the same way that, you know, when I walk through a doorway, if I have I'm not particularly tall, but if I had to duck, cuz it's a short doorway, then I need to duck. That doesn't mean that all humans need to duck or that doorway is a bad doorway for people. Right. Right. If my jeans may be a little bit taller than average, right? So, I mean, a silly example, but

but just because a diet doesn't work for you or Maybe you can't eat gluten or whatever. Yeah, those can be no question. People can have very real, you know, preferences and even tolerances of different diets. I'm not questioning that.

Yeah.

But to use those N of one stories to be like, well, that's why humans have to eat mammoth meat all the time, right? You know, that gets a little silly.

And so, you know, on s sort of on a related note, you know, humans spread all over the world. I mean, that's that I mean, clearly all these different food environments, um, the very different mix of different plants and animals, different parts of the world, and we're very adaptable and changeable. Is metabolic flexibility like itself something that sticks out in humans? Um, for example, I I don't know how much you know about this subject, but like do we flip and flop between ketosis and carb burning faster, more readily than other species?

Uh, so there's no evidence that I'm aware of of ketosis being the standard normal state of affairs for any traditional population. We've measured it in the Hodza. We don't see it.

Um I don't know of any other group that I have any good diet data for today.

And so the the Hodza famously they eat a lot of honey certain times of year, but I guess you would you might argue that maybe certain times of year they're fasting because food is less plentiful or why would they be thought to be keto?

You could expect that, but we have data and they're not.

Yeah,

they're not.

Yeah. Okay. Yeah.

Yeah. So, and we've taken we've we've measured we've done sort of spot checks for ketones and diet and and we've never seen it.

Um, and people say, "Well, you missed it because you didn't do the right test." Yeah, I guess so. But we don't have the evidence.

I I don't I don't I guess I don't understand why that would be some people's expectation. They're living close to the equator. Food is available year round.

Yeah.

Why?

Uh, that's right. So, let's look at the Arctic populations. There's actually been uh evolution in some Arctic groups to prevent ketosis. So, you have these really high protein, high eat fat diet groups like the Inuit, like the I don't know exactly which arctic population these are measured in. Um but but those kinds of ecologies that they actually have a hard time going into ketosis.

Isn't that interesting?

Yeah. Why I mean I don't understand that. Do do we know anything about how that's working?

Uh there's the the evolutionary story there is not clear sort of why that's the case. Um there's been an argument made. These are all handwavy kind of speculative arguments about it having um you know interactions in other aspects of physiology. I I don't actually know. I don't think anybody really knows.

But we do know that it's been measured and they're not going into ketosis as quickly as someone other people

Yeah. Dogs, by the way, you know, carnivores that eat only meat, they don't like going into ketosis either.

Is it because they just have like is is there high protein, highfat diet, is there an adaptation there where they're they just have like stronger gluconneogenesis or something where they're they're actually making carbs from

that's going to be a part of it. Yeah. Yeah. I mean, for dogs, I don't know about the human population. I don't there's evidence for better gluconogenesis in those populations

but that could okay so that could be a potential explanation we have seen something like that in other species

sort of I mean that's the very it's speculative perhaps

uh we know that uh when we measure ketones in other apes so for example that the classic work on this is in orangutans that they go into ketosis when they're starving right uh so we talked about the metabolic adaptations in in orangutans already a little bit um they have these kind of boom bust cycles of fruit availability when there's no food in their forests that they live in in Southeast Asia. Uh they will go into ketosis and so going into ketosis is not unique to us. Um it's not something that we see paired with high meat diets.

I see. Yeah. So that's the surprising thing.

Yeah. And we don't So you know the So can people go into ketosis by having a a zero carb very low carb diet? Yeah. Of course.

Yeah. Yeah, because your your body has nothing else to use for energy and we but to say that that metabolic flexibility is unique to humans is something surprising is something about being having a meat-based diet in the past. Uh none of those explanations in my I don't see the I don't see the evidence for any of it. I'm open to it. I just don't see the evidence for it.

I see. So basically uh people have Okay. So So there there are basically carnivorous medating species And they don't necessarily they're not necessarily in ketosis all the time. So it's not like one thing implies the other automatically.

Exactly. And we don't have any evidence of you know the other piece of this is people use hunting and gathering groups as models of health and what it should be like what you should be eating.

Mhm.

And if that's your model then you have to also accept that none of them are in ketosis.

Right. So um if somehow the healthy way of living that is the human natural way is this vision you have of modern you know foragers and farmers um then you also have to accept that that natural modern way of living doesn't involve ketosis at least as a you know as the base state

yeah so the so the other thing I'm just going to repeat because I I didn't realize this even in populations that are eating a high almost entirely animal-based diet high protein high fat very low carb at least most of the year like the Inuit they don't seem to be going into ketosis or there's I don't know if they never do but there seem to there are definitely adaptations in in in those some of those groups at least it hasn't you know these are things have been measured in a particular population so I don't want to know I can't say that it's

yeah

across the whole Arctic

yeah

but there are are adaptations in at least some groups to to not go into ketosis as readily

h interesting um so shifting focus now to present day humans and questions so civilization develops we have technology now we're all sitting you know in our offices doing Zoom calls all day

we've got this obesity epidemic. So, we've set this up a little bit. Humans seem to be more predisposed to just storing fat compared to other apes.

Yeah.

Um, that might have something to do with what we're going to talk about. Obviously, our lifestyles have changed drastically in the last couple of centuries.

Sort of what I'll just call the traditional naive model in a lot of people's heads, not necessarily people who study this

for why we have obesity is that, oh, well, it's simple. Food is more readily available and we're eating more of it and we're also moving less. So, to solve obesity, you just have to get people to eat less. and move more. So with that in mind, like first of all, can you just kind of critique that model and what's been known about to what extent that's true or not true uh up until recently?

Yeah. So um yeah, the standard like WHO, World Health Organization, you know, CDC, whatever your public health guidelines you want to reference, uh they all say the same thing, which is that obesity is this 50-50 kind of problem. It's it's diet and activity in inequal measure. It's usually how it's framed. Um we actually know for decades that exercise is really important for your health. If you're not moving, you're not active, that's not good for you. But we also know that it doesn't correlate to, you know, to to body weight control in a in a easy way. So, if you are more physically active, you're exercising more. It isn't necessarily going to keep you from becoming obese. We know that it's a exercise by itself is a pretty poor tool for trying to reverse obesity. Doesn't work for most people.

So, if you're obese or you're putting on weight and you want to go in the opposite direction. If all you do is exercise 20% more, there's actually not a lot of good evidence that you're going to lose 20% of your weight or or very much at all.

Exactly. That's exactly right. Yep.

Okay. So, um so, so unpack this a little bit more for us. So, so what have we known about, you know, what what moves body fat in humans?

Well, diet's the main thing. Uh you know, there's been some mudding of the waters over the last couple decades for various reasons. Um the idea that, you know, somehow calories aren't calories or humans don't follow the laws of physics or something like this. You see variations of this idea. Um but it really is the case that all of the calories that are you your body weight and you know your fat all the calories stored as tissue are calories that you ate and didn't burn off. That has to be true. And so your body weight really is a balance between how many calories you eat every day and how many calories you burn off. and the fact that we can't really move the needle on, you know, with how many calories you're burning very well. We talk about that, get into that detail. Um, but it seems like the energy that you're eating, the dietary energy is really what's pushing obesity. Um, and so we have, you know, lots of evidence for that across for decades that that diets work if you stick to them. Exercise doesn't.

So, so people are eating more today. No question about it. Um, you know, caloric intake has gone up. Um, but what we also changes. We'll probably come to that. Let's let's dig into what you said around movement and exercise there because this will probably surprise quite a number of people that hear this.

What were you what were you getting at just a moment ago when when you said the exercise on its own, even if you stick to it, isn't often going to be sufficient to do what people want it to do.

Yeah. So, um well, I'll start off with how I got into this issue, which is um we wanted to understand how many calories you burn every day if you're a hunter gather. Why do we want to know that? Well, because we know that metabolism is so important. There's so many aspects of evolution and ecology. It's like a central thing you want to know about any species. And we didn't really have a good idea of what it is in our own species.

And I suppose the naive view here going into some of the stuff is, oh well, people move less today. We're sedentary. We've got couches and and nice apartments. Hunter gatherers must have been moving a lot more. And so,

but but what is what does it actually look like when you go in?

Yeah. What does the gap look like? So, we wrote this I mean, the grant is, you know, something I'm going to post the grant online because it's hilarious in a way. Uh, we wrote what we expected to see. We we wrote to the National Science Foundation and we applied for this grant to measure how many calories you burn every day as a hodza hunter gatherer.

Mhm.

Right. Because they are we know we knew going into it and it's absolutely true that they're much more physically active than the standard American adult is or European or anybody else in the developed world.

Mhm.

Uh and we used this doubly labeled water technique. So we had a really precise measurement of how many calories burned per day. Nobody had ever done that with a hunter gatherer group before.

Got it. So same technique you used before with with the apes and zoos but now you're doing it with the Hodza. in Africa.

Exactly. Exactly.

They can they can go out and do their Hodza daily routine the the normal way.

Exactly. Yeah. Yeah. Every, you know, every couple days we get get a urine sample for takes five minutes to do that. Otherwise, totally normal daily life for these guys. And by the way, we're tracking their activity as well with accelerometries and that kind of stuff. So, we we know um you we know how how active they are and they are just as active during this period that we're measuring them for calories as they are normally.

Yeah.

We get the results back. And we were shocked because uh they actually don't burn as many calories as we thought they would. In fact, they burn the same number of calories as Americans do and Europeans do. Um and in fact, by the way, if you don't account for body size, they burn less than Americans do. Why? Because they tend to be a bit shorter, a bit smaller body. I see.

So, yeah. So, people say, "Well, did you account for body size?" And we say I have to I always laugh a little bit because I'm like, "Well, yeah. If we don't account for body size, it's even crazier.

Right. Right.

Um but if you count for body size, they're burning the same number of calories as we'd expect for, you know, for an adult in the US.

That was mind-blowing because they're much more active. They get more physical activity in a day than most Americans get in a week. So, we didn't expect that at all.

Um and that kind of be that was the beginning for me. Other people had sort of seen pieces of this, but this is for me that was the beginning of the aha our bodies somehow adjust to our lifestyles.

Right. Right.

And even when we're physically active, we're not burning as many calories as you'd expect for that increased activity. You know, maybe it's

there's something going on there. And so that became, you know, the last 10 or 15 years of my work is is trying to part of it has been trying to understand that.

Yeah. And so so I mean, let's unpack that for people. So some some populations are way more active. The Hadza are in fact, as you would expect, more active than sedentary, you know, Western Europeans or Americans today. and yet they're not burning as many more calories as you'd expect for that difference in active uh activity. So what's making up for the difference here? Is it a is it an adaptation in the basil metabolic rate? What what's going on?

We've been trying to figure this out for a long time. Uh and it's challenging because um measuring these kind of trade-offs is hard to do. Uh inherently we think that some aspects of resting metabolic rate are are being reduced. So if we look at um the the best data we have comparing active and inactive people um with the you know the best quality data isn't necessarily the Hodza versus everybody else because when we go to the Hodza we do that work in the field you know we're limited in the tools that we can bring with us in the back of a Land Rover into the middle of Savannah.

Um so the best data often comes from comparisons of physically active people who exercise a lot and people who are more sedentary. When you look at those comparisons we see um in some cases we lower basil metabolic rates, although that's not we don't always see that, but sometimes we see lower basil metabolic rates. So, that's a clue. Um,

more active in active inactive people. Yep.

Um, we see uh lower levels of of immune function. So, we see like inflammation gets tamped down.

Uh, we see stress reactivity. You know, the kind of alertness and and that you get when you are stressed, even good stress.

Yes. What's important there, I think you said a lower immune function. The immune system is very expensive metabolically. So that's that's a place where we could be making up for that difference.

Thank you. That's exactly right. And what the biggest things we see are changes in background inflammation which you kind of don't you know that's usually a bad thing to have chronically high right inflammation levels.

So that gets tamped down when you exercise. Um stress reactivity, you know, the cortisol and epinephrine response that you get to stress goes down when you exercise. Those are also expensive metabolically expensive responses. You get less of that.

Yeah.

Um we the um by the way we know that people who produce more cortisol and epinephrine per day burn more energy per day than people who don't

uh for basil metabolic rates. So you know so that is really one place that we could absolutely be saving energy that way. Um the reproductive hormones are also lower in people who exercise more. Uh that's a surprise to some people because they think you know that there's a a certain corner of the internet that's sure that if you go out and lift weights you're going to increase your testosterone levels. Uh that's can happen in the short term as you anabolically build muscle, but actually if people exercise a lot, um testosterone levels, estrogen levels tend to go down, not up because your body's kind of adjusting to that limited energy availability and tamping those processes down. So, and all of that is healthy by the way. All reduce stress, reduce,

you know, it's all good

until you go to the extreme. If you are like Olympic level, you know, distance runner,

then your workload, your exercise workload might be so big

that you actually tamp those processes down too far,

right?

And you get overtraining syndrome.

Yep. And that's where people have like hormone problems and other things that start to go ary.

Exactly. Exactly. So, in my mind, you know, I think before this perspective on metabolism kind of became more common, I think those responses in overtraining syndrome were seen as like a pathology that's like a binary. You're fine and then you're not.

Yeah. Um, and I would say, well, you know, it is true that that's not a healthy way to live, but it's just the end of a spectrum

of of how you spend your calories.

I see. So, if I try and abstract some, you know, a theme from this that I'm hearing, you know, tell me what you think about this. It kind of sounds like if you exercise, the more you exercise up to a point, if you're doing a healthy amount of exercise,

it is decreasing the extent to which your body is doing metabolically expensive things at baseline like in, you know, chronic inflammation related to immune system activity. And therefore, because you're not putting as much energy into those energy sinks, you have more energy left over that can be used for more useful things. And that might play into why you've got a lower body fat percentage, say.

Yeah. I mean, it wouldn't necessarily decrease your body fat percentage because if the total calories burned per day don't change, then you're not going to burn excess body fat off. Um and in fact when we look at people who are more active and less active we don't see a body fat relationship there not strongly.

Um the if you are if you are more active today and you maintain that for the next few years you're no you're no more or less likely to gain body fat as anybody else for example.

I see. So the energy that you're not putting into things like you know the immune system stuff and you know other stress responses and things like that it's not necessarily just gonna burn fat off, but it's going to be left over to do something else.

Well, part of it's move, part of it's the exercise, right? So, if you burn, it's like if I burn my calories in my muscles because I exercise Yeah. then I have less energy to burn in my immune system and everything else.

Right. Right.

Right. So, if I burn more with my muscles,

then, you know, I'll just burn less with other stuff. And the total calories a day, I'm not going to say it won't change at all. If you start exercising today, you get an exercise program and you start going, um, but it won't change as much as you think.

Mhm. And it might not it might not change at all. We do see that where people, you know, they start an exercise program today

um and we look at them 12 months later, they're doing the exercise faithfully.

Their total energy expenditure is the same as it was when they started.

So

before they started actually.

Yeah. So basic essentially what you're saying is the obesity epidemic can't be solved by merely having people exercise more. That's probably going to be a losing strategy in general. That doesn't mean that exercise is bad or not good. But it means it's not going to be effective for this particular outcome. Thinking about obesity more, thinking on the diet side, now let's let's decompose the total amount of calories and the specific type of calories someone ingests. You know, to what extent, you know, how do you think about both of these levers here, the total chloric intake versus the specific type of calories and how much that matters in terms of fat mass gain or loss?

Can I excuse myself for one minute? I have somebody making noise outside my house. Notice all that. I'll be right back.

I'll keep I'll keep uh I'll keep people uh occupied here. So Herman's going to come back in in just a minute. Now we're going to talk about, you know, more specifically how diet impacts atyposity and obesity. To what extent is it about caloric intake overall? To what extent is it about the type of calories that you are consuming, not just how many you're consuming? Um people argue about this all the time. My general perspective is both matter. Uh the total caloric intake matters and the specific type of calories. that you ingest matter. It's not like it's one or the other. Um we'll see how much time we have to dig into this. We've got about maybe 30 40 minutes left here and then we'll talk about a new paper somewhere in here that um man was just an author on that looked at total energy expenditure measurements across present- day humans in lots of different parts of the world. Um well-developed parts, huntergatherer populations, pastoralists and so forth. And so we'll get a sense for how energy expenditure, total energy expenditure, and basil energy expenditure actually vary among present- day human populations. And so, so we'll try and unpack as much as this as as we have time to cover. Um, and we'll talk a little bit about uh maybe ultrarocessed foods and what exactly that is supposed to mean. But for now, we're just waiting for Herman to come back. The reason I'm on a monologue right now is because it takes too much time and effort to go in and cut and paste and and rejigger things. within an episode. So, that's a huge time sync from a production standpoint. That's why uh that's a reason why long form podcasts, I think, have proliferated. It's you get a lot of content in here. You can automatically chop it up with AI into more bite-sized chunks, and it's just too much of a time sync to go back in and microedit every little bit that's going on. So, uh yeah. No, I feel it's like that scene in Jurassic Park where, uh where Jeff Goldlum's character is in the car by himself and he's like, "Well, now I'm in the car by myself talking to myself. I just watched Jurassic Park again the other night with family." Um, so anyways, some surprising things that I I heard um in that talk is, you know, what he said around ketosis and different human populations. I would have assumed as I think many people naturally would that a population like the Inuit would readily or go into ketosis andor more or less always be in ketosis. But it sounds like that's not quite the case. They're not as readily going into ketosis and other species that eat more carnivorous diets aren't necessarily in ketosis all the time as well. I don't know a lot of specifics there, but I do think uh there are some adaptations in other species that speak to that their ability to generate sugars from non-carbohydrate sources. All right, Herman's back now.

Sorry about that. All good.

No worries.

Okay, so basically we're now we're talking about the diet side here. Um, and I want I want to get your take on how you think about caloric intake itself versus the specific types of calories people consume and how each of those is contributing to uh fat gain and fat loss.

Yeah. So uh I don't think it has a big makes a big difference if the calories in terms of just in terms of pure body weight if the calories you're eating are coming from fats or carbs or proteins. Um I mean especially the difference between fats and carbs I think is pretty minimal. Um now that doesn't mean that all foods are equally likely to drive you to to overeat. That's not the point. Um but you know in terms of what a fat calorie is going to do versus a carbohydrate calorie once it's in your bloodstream floating around it's just as likely to get burned or stored. Um and the you know I think in terms of the macronutrient content of the food um and just the general makeup of the food overall. Uh the bigger issues there are you know things like um how much fiber, how much protein content to other calories because I think that helps you I think it affects satiety. So basically the the things that help affect whether you feel full or not or more likely to keep eating. Um are some of them are related to the nutrients in the food but a lot of them are you know the flavorings uh that kind of thing.

Yeah. What we call palatability.

Yeah.

Yeah. So to to what extent is the food palatable which more or less means uh how much do you enjoy the sensory experience of eating it? And and is that enough enjoyment to override your your feelings of fullness?

Right? Let's put it this way. If you you know if you overeat sorry let's say you eat 100 calories of broccoli, right? Um you're probably going to feel pretty done at that point. That's a lot of broccoli. If you eat 100 calories of potato chips, you might very well feel like eating more potato chips. Um, now in terms of its effect on your body weight, that 100 calories is going to have the same effect. If you stopped both of them, then you'll have eaten 100 calories and it will have that you will have had that much more on board. Um, the difference in the foods in terms of your weight is that you're more likely to keep eating after 100 calories of potato chips rather than after calories of broccoli.

And how much like do we have a sense for how much of that is the liking of the taste versus the physical the physical way the processed foods are engineered and how they affect say like satiety hormones and things like that.

Yeah. I mean uh I think this is a this is a good Kevin Hall question. This is a NIH researcher who just recently left NIH. Uh but he's you know this is his one of his big areas of research is ultrarocessed foods and why they push us to eat too much and I don't think we know. So, um, you know, my sense, my intuition, my, if I were to place a bet, the hyper palletability that that they just taste so good, they're actually built to be a little bit addictive. Um, or even a lot addictive, I don't know. Uh, that I think that's that's the main thing. Um, you know, I don't think it's the insulin response. I don't think it's uh any other aspects of it. I think it really is in the brain. the way that these foods are affecting your brain.

So the perception how much you like the veilance of the experience is more positive. The idea would be that you're therefore more strongly motivated to eat more despite your society signals. And then I suppose there could be something going on where the society signals themselves get disrupted by something in some of these foods. But it sounds like

we don't have all that nailed down.

No, I don't think we know all of it for yet. And I and what I hope as we kind of launch into this new era you know, make America healthy again and this focus on diet. You know, I think most of the folks in my world are in agreement that that needs to be a focus of of what we do next in terms of the research into nutrition and health and obesity. Um, you know, whether or not that work is going to get done in a useful way, I think remains to be seen. I'm hopeful.

Um, but I think, you know, if somebody is has in their mind that they already know what the answer is, it's food dyes or it's corn syrup or it's whatever. Uh that's not a useful way to to do the science. I think we have to keep an open mind and and really do the work and ask, you know, do the work carefully to figure out what it is that's making these foods uh push us to overeat.

Mhm. And you know, a lot of people are talking about ultrarocessed foods, processed foods versus whole foods.

Yeah.

I want to get like how do we actually define these things? It's it's like one of those things where it's like I know it when I see it, right? We all have an intuitive sense of a whole food versus a processed food, but when we really get specific about this. How do you define ultrarocessed foods? Is there a clear definition? Is there a nice sliding scale uh rubric we can use to measure this?

I mean, so there are there are definitions out there that people use in these nutritional studies. It has to do with the number of ingredients and the way they're combined. Um, you know, I don't think I could give you I don't think I'd get it quite right if I were to try to rec re, you know, recapitulate that definition, but um yeah, it's the number of ingredients, the way they're combined, that kind of thing.

Yeah. So, intuitively, like the more the more processing steps involved to go from

the starting material to your plate, the more process it is,

right? I mean, you know, if you pick it up out of the vegetable aisle or the butcher's counter, you know, or for that matter, you know, making bread at home, that kind of thing, you know, those are probably not going to reach the level of of being called an ultrarocessed food. Um, if it comes in its own colorful package and the ingredient list is a paragraph, then yeah, pretty good chance you've got an ultra process. food.

Mhm. And do you have any thoughts around so when we think about ultrarocessed foods, there's the amount of stuff we put in there that's uh how do I say it that's supposed to be in there, the calories, the vitamins and minerals and stuff like that.

There's also the stuff that can be lost along the way. Things that you might want in there get lost. And there's also the possibility that uh

other stuff gets put in, you know, endocrine disruptors, chemicals, things like this that don't actually have caloric or nutritional value. How do you how do you think about all those things?

I mean, I don't know that I have any original thoughts on that. Uh those are all potential contributors to why these foods push us to overeat.

Um any of them could be important. I uh yeah, I don't know. I don't think I don't think anybody really knows. So, you know, what can we say?

All right. Well, let's talk about the new uh PNAS paper about energy expenditure um across present- day populations of people. So, you we tal talked a little bit about energy expenditure across species and between uh more traditional uh or past populations and today and some of the life history and evolution stuff, but you guys went out and you did these doubly labeled water experiments to measure energy expenditure in a bunch of different present- day human populations ranging from hunter gatherers to, you know, people in in Western Europe and the US and a variety of others. So, set this up for us. Um what was the basic setup here and what were the sample populations you looked at specifically?

Yeah, so uh this labelled water technique has only been around for a few decades. That's not very long in the world of science and it's expensive and so you know to date it's still and I think it's still true the studies that we do with this technique are usually smallish fewer than 100 people um and you know they are driven by different questions and so there hasn't been the funding or the time or the abil ability to do these sort of broad geographic global you know kind of questions in energy expenditure before. Um but now because the labs including mine but a few others that that do this kind of work uh have decided to work together. It's a really great story about international collaboration to do science. We've all pitched our data together. Uh we built this big database called the doubly labeled water database. It's hosted by the international atomic energy agency uh part of the UN. Uh and you know it's it's available for researchers to use and it has now has over 10 000 uh measurements now of people daily energy expenditures and people across the world in different populations. Um and so the studies that go into that are from a whole range of of sources from the kind of human ecology anthropological kind of research that I do to studies of you know different populations within the US for you know a whole variety of reasons that people might do these studies. Um but but the end result is that we have pretty representative samples of, you know, of of populations from, like you say, from hunter gathers to pastoralists who live with their herds to farmers to people in in poor countries where they're doing a lot of manual labor and farming to people in rich countries with desk jobs. You know, it's it's the full economic spectrum. And so we wanted to ask the question, how does energy expenditure change or vary across that spectrum of lifestyle?

Yeah. And then this relates to, you know, questions around, okay, how much are people eating more or less based on economic development. How much is their energy expenditure varying? Uh let's just start out with the basic and unsurprising things. So how does body mass and BMI relate to economic development?

Right? So the richer your country, the more developed the country you're in on average, the taller and heavier you are and the more body fat you carry.

So basically higher BMI in more economically developed areas. That's unsurprising. One thing that I wanted to ask you about is I'm looking at the graph right here. So yes, on average BMI is higher the more developed uh the places that you're making these measurements. What also seems to be highly variable is the level of variance in BMI and body weight. It looks like the more developed you are, the variance is much higher than in other populations. Is there anything worth noting there?

Yeah. I mean, I think what you're seeing is uh that you just don't see obesity, right? So, the upper end of that tail, the upper tail of the distribution just isn't there in a lot of poorer, less developed countries. And as we all know, it certainly is there. in the US. At the same time, you still have people like you and me who are not, you know, on that obese tale. So, you know, you don't lose everybody who is at what we would consider to be the sort of the normal BMI range, but you gain folks who are above that in the developed countries.

Okay. So, what about um energy expenditure across these different populations? What did you find there?

Yeah. Well, it also increases. So, actually you burn more calories every day on average in the more developed countries because you're bigger. So that's not a surprise, but I think it bears saying because you do see people just saying, "Oh, we burn fewer calories."

Right. That's the

And that's really not true.

Right. Right.

Yeah.

Yeah.

Um

but it's largely just because we're bigger.

Exactly.

Those two things are just tied together.

Exactly. And you know, we actually as we're writing this paper, we kind of went back and forth about how we frame that. Is that like such an obvious thing that we just put it in the supplemental materials and like we talk about but we don't focus on it. And I've had enough of these conversations over the years doing this work that I thought no we're gonna we're gonna make sure that this is very clear and it's a point in the paper that you actually burn more calories not less when you're in a developed country and you know even though you're more sedentary all those things you're actually burning more calories yes by virtue of being bigger but I think it bears saying clearly that you're actually burning more calories not fewer when you are in a more developed country.

Yeah. Yeah. Yeah. And so So um what about what about other aspects of energy expenditure like basil metabolic rate?

Sure. When you so when you correct for so basil metabolic rate is also higher in a developed country again because of the body size thing.

When we account for body size we do that sort of adjustment of our our data to account for the body size effect.

Uh we see two things. Um there is a sort of tiny whisper of a effective development. So um it's a it's a small But when we have thousands of people in this study, over 6,000 people in this study I think um or maybe sorry in this analysis of just adults I think it's over 4,000 people we have with that many people you can detect a very small effect of development on basil metabolic rate. So people in less developed countries probably because they have more like pathogens more germs that they're fighting every day. It's they have higher basil metabolic rates

and that goes down as you get more developed as a result of that total energy expenditure also tips that way. So in less developed countries slightly more energy expenditure. Again it's attributable to basil metabolic rate not attributable to activity or anything like else.

Um and it's it's a really small effect. But the bigger pattern I think is that the variability within a population is much bigger than the differences between populations. And there's no clear evidence of lifestyle effects on any of this stuff. So again we Again, in this analysis, hods of hunter gatherers look exactly like us men and women. Um, and lots of cases like that where, you know, there's there's just no clear effect of lifestyle on energy expenditure period. If you want to look at the tiny effects, they seem to be on basil metabolic rate.

And so again, we come back to this idea that a huge component of basil metabolic rate seems to be energyintensive. Um, I don't know if I want to call it a background process, but certainly nothing that we're consciously controlling like your immune system overall activity which is naturally going to tie into say the pathogen load in the environment you're in.

Exactly. Exactly. Yeah. So there's no not a big effect. You know it's kind of a hodzy result all over again. We don't see an effect of of economic development really. If you look really carefully with a huge sample size you can find a small effect and it's on basil metabolic rate not on other aspects and that kind of bubbles into total expenditure but again it's it's pretty a small effect.

So again uh bigger bigger people have high total energy expenditure which if you think about it makes sense but to a lot of people that will be the opposite of their expectation.

Yeah, that's right. That's right. Um and so we can then ask the question well okay who cares who cares why there's this sort of small effect of of economic development on energy expenditure. Maybe that's enough to to explain this pattern of of body fat that we see across populations. So maybe

even though there's just a tiny little effect of of energy exp of economic development on energy expenditure. Maybe that's enough to explain

because people don't get they don't wake up obese. It's it unfolds day after day, year after year.

Exactly. And so we asked that question last. There sort of three questions in that paper. The third question is if we look at the variation in energy expenditure size adjusted again and ask if that explains body fat percentages or BMIs, it really doesn't. Again, with with 4,000 and some people you can It's a tiny effect. Um, but it's really variable about across populations. Most populations there's no effect really at all. Some are more, some are less. And the bottom line is at most the variation in energy expenditure AC around the globe explains maybe a tenth of the obesity differences across the globe.

Mhm.

And the rest of it again because it has to be expenditure or intake, the rest of it must be intake and diet.

H and so what was what was the relationship you found between body fat percentage and ultrarocessed food intake and how did you actually count and measure ultra processed food intake?

Yeah. So we were left with this analysis that says look the energy expenditure is not explaining body fat percentage. It must be energy intake. But that's not super satisfying because we don't actually measure the diet in this study. You don't have those data.

Okay.

But if that's true then let's find ways to test that you know what we're left with holds water that there really is something there. And so what we did was we went into the literature into the scientific literature and we found good data for every group that we could. It wasn't all of them but it was a lot of them uh every community that we could the amount of ultrarocessed food they're eating for example and asked does that explain body fat percentage differences and sure enough it does. So the most obese populations the highest body fat populations are eating the most ultra processed food and

that's just based on the availability of those foods at like the population level.

So those are those are analyses that looked at uh the percentage of calories in the diet um that are so presumably these are the calories being eaten although I don't think anybody's going home and making sure that you finish your Doritos. So like

it's a food availability measure.

Yeah. Yeah.

Yeah. Yeah. And and and you know what percentage of the calories that you're available to you in your community are from ultrarocessed Mhm. So, um, we've got a little bit of time left. So, what would you say like what is like your over based on everything you've studied? You've got you've got this really interesting picture with your anthropology background of having looked at all of these present day and ancient human populations. You've thought about this

um, you know, over time and across space. What, you know, what what would be like sort of the bullet point things you would say to a present- day person who wants to lose weight or suffering from obesity in terms of what's going to give them the biggest bang for their buck in terms of relatively simple and manageable lifestyle changes.

Sure. Uh first of all, don't stop exercising. It's really important for a lot of aspects of health, but when you want to move the number on the bathroom scale, it's got to be diet. You have to focus on diet. Um now, the good news is that, you know, this kind of tribalized view of diets, it has to be this or it has to be that, you know, is not true. I don't think any evidence for that? Um, any range of diets might work for any individual person. Uh, so people should should kind of shop around and try. I mean, we we do know that eating higher fiber foods make you feel full on fewer calories. Higher protein foods can make you feel full on fewer calories. And that's that's the name of the game. If you need to lose weight, how do you eat fewer calories without being miserable? Because if you're miserable, you're not going to stick with it.

Right.

Well, you know, with that in mind, what what are your thoughts on fasting, like intermittent fasting and timerestricted feeding. Um,

yeah,

to what extent are those useful and and manageable?

Yeah, I don't think there's any magic there. I think the reason those work is they cut how many calories you eat every day. Uh, and for some people, it's a really good strategy that they find easy to follow. Yeah. Easier to follow uh than trying to sort of cut 10% out of every plate of food or something like that.

Uh, and so, you know, the benefits are there. If you if you can reduce how many calories you're eating every day, you're going to see the same benefits. Whether that's because you went with time restricted feeding or with a a no carb diet, sometimes that works great for people. But no problem with for me with that if that's what works for you. Um, Mediterranean diets work better. You know, it depends on what kinds of foods and what pattern of eating is going to keep you the healthiest. I know that for me, uh, one thing that I pay attention to, um, if I, you know, trying to to watch calories for some reason is how much do I eat while I'm watching TV at night, right? I come home at the end of the day, I got two kids, I'm dealing with them. Uh they've got a lot going on, which is wonderful and fun. Um but by the time they're in bed, I'm exhausted and I just want to zone out for a while,

right?

And in my zone out time, if it's TV or whatever it is, often, you know, that comes with a snack. And it doesn't have to, but it will if I I you know so if that's one great easy way for me you know to watch how many calories I'm eating is is am I snacking or not. So anyway there's different ways to do it and I think if you are trying all those things if you've tried all those approaches all those lifestyle interventions and you're still struggling um then you know I honest I'm a big proponent um of the new class of weight loss drugs GLP1 and and GIP drugs um I have no investments in any of them. I'm not making any money off of them. I can promise you. Uh but to me, you know, as far as I read the data, they seem really promising. They work for a lot of people and they work by keeping your brain quiet and not, you know, pushing you to overeat. So, I think um you know, I don't think those should be the first line of of approach. I think lifestyle is always the better way to start. Um but I think those drugs have been a real gamecher.

Um you look like you might be like me and that you're a naturally lean person. Um I don't seem to be particularly prone to putting on a lot of body fat.

Are there are there people that are just naturally more resistant to developing obesity? And do we understand why?

Yeah, absolutely. We know from looking at the genetics of of you know, obesity that there's a you know, you come into the world kind of wired in a way that makes you less or more likely to to struggle with that. Um it has all the evidence points to the brain and how the brain is wired as being you know, the the the the organ where this is happening. Um, and you know, I I can say that anecdotally this bears out for me. Um, I don't Yeah, I haven't ever struggled with weight. I've been very lucky that way. Uh, but part of it is that I just don't care that much about food. Not as much as I know, you know, my my wife is also lean and in a healthy weight, all that kind of stuff, but I know that she just thinks about food more than I do, you know. what's the snack she's going to have? What were you having for dinner? Those are on her mind in ways that aren't on my mind. And um I think that that's you know kind of I guess gets anecdotal, but it's I think it's that kind of microcosm of what's going on larger in a larger picture. But

um it it sounds like what you said a moment ago is so there's been you know genetic studies where we look at okay some people seem to be more naturally lean or more prone to obesity. There are genes that correlate with that. If if I was picking up what you were putting on there. A lot of those genes are genes expressed highly in the brain.

Yes. Exactly. That's right. That's right.

And are there any are there any important call outs there? Are there any clear patterns as to what exactly what circuits are involved or what exactly those you know proteins and things are doing?

I think for that uh set of questions the better evidence is from you know the work done on like the hypothalamic signaling in mice and some of it's done in humans about brain signaling in parts of the brain where where you're active when you're eating and hungry. Um so I don't think genetic work. I might be wrong about this, but I don't think it's quite connected to brain regions and pathways exactly yet.

Uh, but there's other work there that says and including actually the success of the GLP1 and GIP drugs. I'll also point to this that it's that hunger and satiety signaling and reward centers within the brain that are kind of where the, you know, the crossroads for all this. It's never going to be one simple thing, right? It's a bunch of different factors.

Yeah.

And I imagine those things are are tied together intimately because, right, your hunger and satiet the hypothalamic you know hunger and satiety circuitry let's just call it is you know it's bound up with the with the reward processing palatability perception stuff

exactly that's exactly right and I mean I think that's why the GLP1 drugs for example uh are not only effective for weight loss but you know these they have these interesting side effects of people using less alcohol using less drugs doing you know gambling less like you see every seems like every week I see some new headline about these knock-on effects and they all seem to be brain related.

Yeah. So it might be generally it's not just boosting satiety itself. It might be reducing reward sensitivity and that includes food rewards, drug rewards, etc.

Exactly. That's what the data point to. This isn't what my work but you know I'm reading the literature and that's what I see.

Yeah. Is there any possible concern there given that these drugs are new that the ic effects might be something to pay attention to especially given the history of weight loss drugs like Romanov

100% we need to be careful absolutely uh and you know I think we need to keep on monitoring what's going on um a couple things that make this I think more likely to to end up looking like it looks now which is a pretty safe way to go uh which is that these drugs first of all they're mimics of hormones that your body makes already

so that's one I think indicator that this is probably a promising therapy that way. Uh they've been around in various forms in human use for medications for over 10 years. The new injectables are pretty new, but the there's other ways of getting that drug like rebelsis is a diabetes drug that uses the same basic shape of a drug that that has been around longer. Um and you know the so far the safety profile looks pretty promising. I I'm with you. You know that that we have to be careful about this and need to keep monitoring. They don't get a free pass for surely. Um, but I will say that we also know that the long-term health risks of obesity are not to be overlooked. I mean, those are serious. And so, um, you know, I think if somebody's already at a healthy weight, I wouldn't play with these drugs. It's not not worth it, right? Uh, but if you have a serious issue with obesity, we know that those that carries health risks, then you know, I think that the health the costbenefit analysis might change.

Yeah. Yeah. Um, do you want to say anything more about your book and what's in it? Um, and kind of just reiterate what it's all about.

Sure. Um, yeah. So, it's adaptable. Um,

put it right parallel with your face so it's not like this.

Yeah. Yeah. Let me see.

I don't know where I am.

Move it. Move it. Move it closer. Actually, let me see. Move. Move the book closer.

Oh, like this.

Yeah. No, you had it for just a second. And it's blurry now.

Ah. Oh, it's blurry because my background's blurry.

Yeah. Yeah.

Oh, sorry.

Oh, right there. Right there.

There. There. There you go.

Okay.

Talk with it right there.

So, Adaptable is uh a book about how your body works. We get into metabolism, of course, and diet, but we get into everything. How brains work, how muscles work,

um how growth works, how immune systems work. And the idea is to give people in in the same way that I I've tried with my work in metabolism to give people a a fluency in how energy metabolism works and and then I'll talk about too why that matters for obesity and health. Um I think there's a story there in every aspect of our body from our again our brains to our muscles to growth to reproduction to immune systems all of it's important right and I don't what I don't see out there um in the influencer sphere is a lot of people talking about you know how our bodies work kind of at a fundamental level that's going to give people the fluency they need to make good decisions about lifestyle, about health care, about the big dis, you know, discussions that we have uh in the US surely about things like IQ, race, gender, and and sex. Um when does life begin, right? All of these big issues fundamentally rest on how we understand our bodies and how our bodies work and how they work differently. Um and so, you know, the book isn't trying to get people to think like me or anything like that. Uh it's not meant to sort of push you to to have a particular set of opinions. But what I do want people to have is a shared uh space, a shared set of evidence and facts and fluency in how our bodies work that we can use to all have this discussion together in a more useful way.

All right. Well, Dr. Herman Poner, thank you very much for your time.

Thanks for having me. It was fun. I want to take just a minute to tell you about a really cool health monitoring device I've been using called Lumen. It's a handheld pocket-size device with a sleek design. The Lumen device measures CO2 levels in your breath, which allows their technology to determine the extent to which your body is burning fats versus carbohydrates. Lumen helps improve your metabolic flexibility, your body's efficiency in shifting between using fats and carbs for energy. I use this device in the morning or before bed or after meals or after workouts to track my metab metabolism. With just a couple weeks of use, I learned a lot about which foods were causing my body to burn mostly fat, mostly carbs, or both, as well as how long I needed to fast and how hard I needed to exercise to promote fat burning. Being able to track whether your body is burning fat versus carbs will help you figure out how your body responds to your lifestyle and whether or not your weight loss and fitness strategies are actually working. Lumen is great for anyone looking to optimize their health for either weight loss or athletic performance. Their easytouse app allows you to track your results together with what you're eating and how you're exercising and it syncs with other devices like the Apple Watch. Click the link in the episode description to learn more and use the code mind matter m i n d m a t e r to get 10% off your Lumen device today. That's on top of the sitewide sale they are currently running and the Lumen device is eligible to be paid for with FSA and HSA health accounts. Check out the link in the episode description for more info.

TRANSCRIPT 2
Eugene Morin 2:27

Well, I'm a Paleolithic specialist. And I study animal bones, mostly in Europe, more specifically in France and Montenegro. And you know, I started working about 20 years ago. I'm a specialist of Neanderthals and early modern humans. And I focus my I would say most of my research focuses on diet subsistence foraging. And I do a bit of more and more I would say over over the years I'm doing more and more ethnography and that no history. So the study of a non western societies, and I tried to use that as kind of framework to help me interpret the past.

Nick Jikomes 3:14

Is there a particular period in time that you focus on?

Eugene Morin 3:17

Yeah, so when I send you out to doors and early modern humans, so I study mostly people who lived about 200 to 50,000 years ago, that's basically the range I work on. But I've worked on stuff that is like, almost 600,000 years old. And

Nick Jikomes 3:36

would this be the Paleolithic period? Yeah. So

Eugene Morin 3:39

that would encompass the lower middle, and Upper Paleolithic as well. Sometimes I work on on later stuff. So but mostly it's it's the Palaeolithic, I would say the later part of the pelvis. And

Nick Jikomes 3:52

can you can you just talk about like, what is the Paleolithic era? When did it start? When did and and what defines it? Are there particular archaeological discoveries or events in history that that start? Yeah, yeah. So

Eugene Morin 4:05

the public starts as soon as we have them any cultural objects. And so objects made by humans with the goal of assisting them in their activities. So in Africa, it starts about 3.3 million years ago. And we usually take the arm emergence of agriculture as the end of the time period. So it's occurred about 12,000 years ago, in the Near East. I see. So basically, 3.3 million years ago to 12,000 years ago, that's the prolific.

Nick Jikomes 4:39

I see. And over that period of time, really just in very general terms, where were humans coming and going. So at the beginning of the Paleolithic were were humans was our lineage of humans. And by the end, where were we across the globe? Yeah,

Eugene Morin 4:53

so the prolific it's a world of hunter gatherers, okay, so there's no agriculture and It starts in Africa. And we have hints that there there are some expansion of dominance out of Africa, starting probably around 2.5 million years ago. So they start to colonize the, you know, eastern part of, sorry, the southern part of Europe. Well, it mostly southeast, sorry, Southeast Europe. And then they move into the tropics of Asia. And so we find them, you know, probably around 2 million years ago, 2.5 million years ago, in southern Southeast Asia. And then the two continents, continents are populated later. So Australia would be probably occupied around 45 to 60,000 years ago. And then we have occupation of the Americas. About 25 to 30,000 years ago,

Nick Jikomes 5:58

the first species of hominids that were leaving Africa, what what subspecies would that be was that Homo erectus? Was it some other species? Well, that's

Eugene Morin 6:09

that's a good question. People are debating this. So some, you know, some people have argued there possibly later, you know, the very late Pleistocene, sorry, very late Australopithecines. Other people think it's only early almost that we're moving out. So that's still debated. I think on the safe side would say these are early Elmo populations.

Nick Jikomes 6:32

When we think about the evolution of the genus Homo, that would include ourselves that would include Neanderthals and other things. What, what are some of the key phenotypic features of this, of this genus that distinguish it from other mammals? In particular, I'm hoping you can start out by talking about like physical adaptations, muscular skeletal adaptations, aspects of the body that relate to how we move throughout the world. What are some of the key adaptations of homo?

Eugene Morin 7:02

Well, what we see in early amo, is there, you know, we see first they're getting taller relative to Australopithecines. So I'll strip it, the scenes are basically the height of mother and chimpanzees. And so with early on Mo, we see people are standing up, and now are close to, you know, our height. We see in their body that, especially with OMO rectus, the postcranial, that is down the neck, we see that they are having a features that are similar to what we see today. So most of the changes that we see in early hominids do occur before they move out. These hominins moved out of Africa. And so basically, it's quite similar. We see throughout the Palaeolithic, you know, and enlargement of the brain. So that's really a major change we see. And contrary to what has been thought, you know, a century ago, and even perhaps even 50 years ago, is that what we see is that the brain comes late in the store the human story, the enlargement of the brain, as we have tools way before we have large brains.

Nick Jikomes 8:12

What were some of the like musculoskeletal changes that happened that enabled homo, generally, in Homo sapiens particular to be a hunter gatherer species tend to engage in the types of foraging and hunting behaviors that are typical of humans.

Eugene Morin 8:29

So what we see in humans that is very different from other mammals is that we have two key features that are quite distinct. First, we have the about the ability to sweat a lot, okay. And this might seem, you know, not particularly adaptive, but there's a good reason for this is that humans need to, well, in collage activities, you need to disseminate a to dissipate heat. Okay, so if you're, for instance, if you're running, and you're running for, you know, extended periods of time, what will happen is that your body will build up heat. And if you don't have this, you know, an efficient way of evacuating this heat, you will overheat. Basically, think about the car that has no radiator, you know, you can do so much, but at some, at some point, the heart the car will overheat, and you will, you will be forced to stop. So that's the same thing with our body. So we need to evacuate this heat. Animals like cheetahs are an example. It's a very good example of an animal that can sprint very well that you know can achieve almost 100 kilometer per hour, but this animal cannot sustain prolonged activity for more than a few minutes. And then the they become, you know, they overheat. So that's one feature, this ability to dissipate, you know, building heat. The other feature is that we you know, our locomotor muscles. So the muscles that help us to move there are dominated by what we call slow twitch fibers. Whereas most other mammals have fast twitch muscles. So these ones that fast, which one are related to power. So for instance, if you will need to sprint, you will use these fast twitch fibers. And what's interesting about them is that these are, you know, they will use the stored glycogen in the muscle to fuel them. Whereas humans will use the slow twitch fibers, which are fed by our breathing. So, in other words, when we, when we run, for instance, you will note, if you're running the first 30 seconds, your your breath, you know, your breathing rate will not change. That's because you're still working on the story, glycogen. But when you start to breathing to breathe heavily, that's because now you're starting to use the oxygen to help transport the glycogen to the muscles, okay. And so that's why that's one feature that is very distinctive of humans is that we use the slow twitch fibers way more, and we have more of them. So

Nick Jikomes 11:13

you've got slow and fast twitch muscle fibers, they have different physiological properties, I would assume that all amp, most mammals probably have some amount of both, but what you're saying it sounds like is that humans are proportionally more of the slow twitch fibers compared to the fast exactly

Eugene Morin 11:27

and more relative to our close cousins, too. I mean, to chimpanzees, like for instance, if you are involved with a, in a fight with a chimpanzee, you know, you will, your button will be kicked, they they're really, really strong, much stronger than humans. And that's because they are, they are among other reasons that they have a lot of fast twitch muscles. Whereas humans, as I pointed out, you know, they have the slow twitch muscles, and that allow them to run for longer, with minimal use of fuel.

Nick Jikomes 11:59

I see. So if you try to fight a chimpanzee head on, you're gonna lose because they're way stronger, because their muscle composition, and other things are different. But if you run away, you probably have a good chance of getting away. Exactly. That's perfect. That's exactly it. And so if we sort of put all these things together, so we have this ability to sweat a lot, which enables us to dissipate heat, so we could move around in the environment for longer without overheating. We also have more of these slow twitch muscle fibers, which are less about power and and strong bursts of energy right now. And they probably enable the slow twitch fibers more long term, locomotor activity. So does this point to and enhance the ability to engage in long distance running and and something that might relate to certain forms of hunting.

Eugene Morin 12:47

Yeah, that's exactly it. So Deus, the these two features indicate that there was selection for stamina in humans, okay, that power, but stamina. And there are a few context, you know, few activities that that would require that kind of stamina. And an obvious locus of selection is hunting, and possibly scavenging. So we can imagine that humans found a niche in which, you know, running, you know, how hours and after hours after long, you know, large prey was a locus of selection, and a niche that was not occupied by other mammals. And so that's what we think we happen with, you know, or at least, these are factors that probably contributed to the evolution of these traits in humans.

Nick Jikomes 13:37

And sort of related to that, you know, I've seen some interesting data around some of our metabolic and physiological adaptations, particular things that have to do with our digestive system. So if you just sort of take a broad view of human digestion and metabolism, and you asked things like, what is our gut look like? How long is our GI tract? What is our stomach pH, all of these types of things, and you compare it to other mammals, herbivores versus carnivores versus scavengers? What sort of metabolic profile or digestive system would you say humans have in comparison to other mammals? And how does that maybe sort of tie into some of these physical adaptations that tell us about what early humans may have been adapting to in terms of diet?

Eugene Morin 14:23

Well, that's not my area of expertise, but that, you know, some notion that I'm aware of that then I've worked on, for instance, if you think about pH, you know, our pitch is not that different from that of, let's say, over wolves, for instance, who are, you know, noted for sometimes scavenging, and so, or highness, so in that respect, we're not different. Vultures have really high pH. So these are literally animals that looked at low pH or high pH. I pH so they can so they can I'm sorry, low pH does so they can they can process these, you know, very rotten meat in a way that we cannot. So no, sorry, low pH, low pH, high acidity. Yeah, exactly. So they can tolerate very, you know, acidic things. And so that helps them to process a rotten meat. And so this could also be, you know, in some way related to our ability to use to use scavenging as an a form of meat procurement method. So that would be one thing. Other people think that our gut became larger for processing complex carbohydrates. And that might be related, for instance, to an increasing use of plants and plants that, you know, contain toxins, the the invention, or I would say the discovery of fire and the use of fire could be related to an attempt by humans to attempt a sorry, as an attempt to reduce toxicity of plants. And so cooking helps in this way, because you, you can get rid of the officers some of these toxins by this way,

Nick Jikomes 16:15

when when we're humans first using fire.

Eugene Morin 16:19

Well, that's a very controversial problem. There's, I would say there's a safe answer. The the safe answer is that's at least 400, maybe 500,000 years ago. Now, there's another answer, which suggests there might be some evidence for us, but that would say, on an occasional basis, maybe ad hoc basis, and that could go as far as some say, 2 million years ago. So steady, consistent use of fire is recent fire hunt may be no more than 500,000 years old. But regular occasional use could have occurred or a little bit earlier. But again, that's debated. And one reason it's because many fires might have been very ephemeral. And they might not leave an archaeological signature that are quite robust.

Nick Jikomes 17:16

I see. So so we know, it's at least at least a certain amount of years old. And it might be older, but we just can't detect it, or andorre. Humans weren't using it frequently. Yeah.

Eugene Morin 17:27

Yeah. And it might have varied regionally. It's just that by 400,000 years ago, we're fairly certain that it's being mastered in many regions of the world, and that it's a habitual behavior. And

Nick Jikomes 17:39

is that unique to Homo sapiens? Or did other species of Homo have fire as well?

Eugene Morin 17:44

Well, we sit in the earth, Some see it as a different species, some as a subspecies. So that depends on your view, or more practice us, if we say 500,000 years ago, that's, that would be a more practice. So you know, we can you imagine that it's, you know, was used by several species. For instance, we know of The Hobbit, the so called Hobbit in Southeast Asia, it's unclear yet if they use fire, but that would be another species. So

Nick Jikomes 18:16

we have humans have these adaptations that enabled stamina, we could run long distances, we could dissipate heat efficiently. We had the muscle composition that that enabled all of that. It's presumably related to food procurement, whether that's active hunting, or scavenging for these early humans in Africa, in the Paleolithic, do you have any evidence, any good evidence as to the types of creatures that they were hunting or scavenging the types of meat they were eating or anything like this?

Eugene Morin 18:47

Yeah, so we didn't know what, what range of species they're hunting. So if we go back to Money and years ago, it seems that they are already able to procure some large game, such as gemsbok or are to be store, you know, and in some smaller ones, probably dykers, these animals were probably in the range of what they could acquire. A Elans are also thought to be sometimes acquired, but there's some debate about the larger range of the larger game. Something they were probably scheduling scavenge more frequently than the than, but so it's unclear, but at least for the medium size, animals, you know, something like maybe a gemsbok that seems to have been in the range of what humans could could acquire. For those who are unfamiliar with the species. James Bach would be about the size of, let's say, caribou in North America.

Nick Jikomes 19:48

A big deer. Yeah, so

Eugene Morin 19:50

a big deer. Yeah.

Nick Jikomes 19:51

And do we know like, when, when these early humans were hunting was was meat like that? Was it an occasion No treat that they would get whenever they could was it a very? was? Was it a staple of the diet? How like, what proportion of the diet came from hunting? And do we know very much about like the full composition of these early human diets? That's

Eugene Morin 20:13

very difficult to answer. We think that they, you know, if they show up in the archaeological record, it means there, you know, it's more than occasional. But whether this is a staple that remains to be determined, we have quite a few evidence, you know, that they're, you know, like, we have slice marks or tool marks on bones that suggest they're using different species. We know they're extracting marrow, very early on by a 2.5 million years ago, they're already extracting marrow. In fact, that might have been one of the main incentive to on these animals to get fat, because marrow is full of fat. So fat is often more important to modern foragers than the acquisition of meat, actually.

Nick Jikomes 21:00

So it sounds like there's, you know, it's hard to get a lot of direct evidence for this stuff. But we have things like bones with cut marks. And it's common enough that when you see it in the market, archaeological record, it couldn't have been rare, because otherwise we just wouldn't find artifacts like that. Are there also indirect sort of measures of this type of thing? So for example, I know that when you look at cave art, a disproportionate of the cave art seems to be centered on animals that presumably would have been hunted. And that would suggest that perhaps it was quite common. Yes,

Eugene Morin 21:31

so there's cave art, but before we addressed cave art, there was also some isotropic studies. So when you eat certain animals, or certain types of resources, you will acquire some, some isotopes through the tissue. And this might, you know, be detected by looking at. And by extracting collagen from the bones, you might be, you know, we're able to make some inferences. So we know when we look at early dominance, it looks more like they're eating plants more. The acquisition, or at least the procurement of game seems clear in the totals. So it seems to be effort, you know, in fact, near those have been described as hyper carnivore, which is probably, you know, a stretch, but there are definitely, you know, having meat on their regular basis. So probably why I would say by, I would say, five, 500,000 years ago, humans eat meat on a regular basis. Now, with respect to cave art, the oldest cave art is about 5050, maybe 55 60,000 years ago, 60,000 years old. And what we find the earliest ones are not depictions of animals, they're often dots or hand stencils. So the cave art with representation of animals slightly younger, maybe 45 40,000 years ago. And, you know, we see a range of animals often they are spectacular ones, we have Bisons, you know, cave lions, stuff like that. And whether this indicates that people are trying to acquire these animals, or they are somewhat scared by these animals are trying to acquire the power of these animals is, of course, a matter of debate. And the true meaning of this cave art remains a little bit nebulous to us. But what's interesting is that when you look at the, you know, the skills that are shown in these things, you know, early on, they look like, you know, Leonardo da Vinci, they often some of them are really the already beautiful and spectacular. So it

Nick Jikomes 23:49

sounds like the earliest hominids, were eating mostly plants, maybe occasional meat. So, you know, in broad terms, probably not that different from something like, you know, great apes like chimpanzees, mostly, mostly plants, but some animal based foods. And then, as our lineage emerged homosapiens, Neanderthals, we have these adaptations that allow, you know, we had bigger brains happening, we had the ability to have more stamina evolving, that unlock the ability to hunt. And so meat became more important in our diet than it was for other apes. But we're still eating an omnivorous diet.

Eugene Morin 24:25

Yes. What's important to emphasize on this point is sometimes overlooked is that chimpanzees and bonobos, which are our closest ancestors, they both hunt not on very frequently, but they will they will hunt, especially red colobus monkey, sometimes dykers which are small antelopes, they can acquire turtles, so they can hunt and they're successful to some extent, is highly variable regionally, some population will hunt more frequently than others, but Did there it until maybe 20 years ago, it was thought to be extremely marginal. And now, you know, there's some evidence that in some population, it's it's a, I would say, a treat, you know, something not common, but it's definitely there. So in other words, humans are not qualitatively different than that respect from the apes unbeknown boasts, it's more the extent and the size of the of the animals that we capture that is different. No, chimps will capture something as big as a caribou. You know?

Nick Jikomes 25:36

Because they don't have physiological adaptations that enable them to catch an animal. Yes.

Eugene Morin 25:40

And also because they don't use tools for that. And you know, are they use very simple, you know, it's not exactly true, they do use some tools, but often is for acquiring, you know, the tissue itself. So they might, you know, they might bang a Turdus on a tree to open it and stuff like that. Or there's some suggestion made it sometimes they may be using stones, but it's unclear, you know, to what extent they use tools. But overall, when we look at them, it's mostly catching by the hand, which limits what you can do. Humans use projectiles, they use snares, they use traps, and other methods that allow us to overtake you know, prey that are much larger than ourselves.

Nick Jikomes 26:28

And what kind of artifacts do we have for the tools humans were using for hunting? When it became more common? Were they using spears and projectiles like that? Were they also using traps and other things? What was their preferred method for selling game? That's

Eugene Morin 26:44

an excellent question, one that, you know, I've been working on for a while. The oldest tools that we have the oldest spears are about 400 300 400,000 years old. We don't have any ball on our road that are older. Some say that they're already present by 60,000 years ago. And directly based on the size of the of the spear points, or the arrowheads for snares, and traps. These are very ephemeral products. And so we don't know at all, when they were used, I assume they're quite old. We know indirectly, there's some figurines made of clay, in grievous in context, so about 30,000 years ago, and these figurines, they show nets on the hair. And so these nets, you know, if they were used for, you know, as a, as a piece of, you know, you know, as clothing or so on, or at least using for clothing, it's possible that the could have been this, these skills could have been transferred to Ponting. So we could assume that there are nets at least 30,000 years ago, but for anything older, it's the question is open.

Nick Jikomes 28:03

So, you know, roughly half a million years ago, I think is when our lineage diverged from Neandertals. And so we sort of go down two separate routes to some extent. Neandertals get to present a year before our lineage, I believe. And eventually, our lineage goes out of Africa, goes into Eurasia, and eventually moves West and colonizes what is present to Europe, and they encounter Neanderthals along the way, as Homo sapiens was leaving Africa and starting to populate Eurasia and into Europe. Do we know anything about their diet and how it might have been changing over the course of that period?

Eugene Morin 28:42

Yeah. So when we look, first of all, what's important is that there was the divergence between our thoughts and modern humans, but they're also some significant gene exchange. That's why we see they call it introgression. So we have some evidence that there's you know, it's not to population completely diverging, there's some divergence, but also some exchange of genes in the process. Now, with respect to their diet, that's a topic that I've worked on. We don't see any major differences in terms of what modern humans and Neanderthals eats. In fact, there's almost a complete overlap in terms of what they do have a focus on the same kind of tissue, same kind of animals, their transport behavior is similar. So they transport the same element, usually for fat, so there's no on this on the basis of subsistence, there's no striking difference between the two population, either Neanderthals or modern humans.

Nick Jikomes 29:42

And how like, what were they getting most of their fat from animal products?

Eugene Morin 29:48

That's a good question. In southern Europe, it's possible that they got some through nuts, okay. You have some fat and nuts but it's it's presumed that Most of the fat came from marrow and the subcat cutaneous fat that is the Mac fat that we see on animals.

Nick Jikomes 30:08

In what so, you know, so there was all of these integrations, at least sporadically between Homo sapiens and Neanderthals, we exchanged DNA, you can still see evidence of Neanderthal genes in you and me today. How often do we think that was happening? Was it pretty rare? Was it can you give us like a sense for just how rare or how common it might have been?

Eugene Morin 30:31

Well, it was really quite rare, because if not the two population, you know, the genome would be more similar. In fact, it would be identical if it was very common. So there's enough for divergence to occur. But there was enough gene, or gene Exchange, which could have been maybe once a generation in between two population. And this was enough to prevent full divergence and respect. And it's unclear still, what happened to the last near adults. I'm, you know, some people think it's related to in fact, a different mode of survival, sorry, a different life way that was promoted by the modern humans when they invaded, and that these, you know, cultural that dictation allowed them to overtake Neanderthals. In my opinion, I think it's related to the habitat that was occupied the Neanderthals, I think the habitat became, in some way, there was a climatic deterioration, about 45,000 years ago, that was probably severe enough, that the population became very small. And this could have led these elite to small population simply collapsing because there's not enough gene flow between different groups. So in my opinion, environment, you know, ecological aspects or environmental aspects have been neglected in that in that respect.

Nick Jikomes 32:01

So can you give us a sense for the time period in which there was the most overlap between homosapiens and Neanderthal populations was it was 10s of 1000s of years? How far back to that stretch?

Eugene Morin 32:13

Yeah, if you go if you're in Southeast Europe, and then the areas, there's evidence of Neanderthals and modern humans for at least 50,000 years, if not more, okay, and maybe some say, even 100,000 years. So there was significant overlap in terms of the use of these two areas. Now, with respect to whether the made contacts and everything that's difficult to say, but in these regions, the stone tools made by inheritance and modern humans are not different or not, we cannot distinguish them. So this suggests there's some form of cultural trends of cultural transmission between the two groups, or at least diffusion of ideas that, you know, crossguard these boundaries are these genetic boundaries.

Nick Jikomes 33:02

So it sounds like you've told us so far that Neanderthals had a very similar diet to Homo sapiens. It sounds like we're using the same hunting tools, and therefore, we would have had comparable hunting abilities. We know that they had big brains. What about culture? To what extent did Neanderthals have culture? Do we see them using art and ornamentation and the types of markers that Homo sapiens groups use to define one group versus another group? 20 years

Eugene Morin 33:33

ago, 30 years ago, the answer was no, Neanderthals didn't have much of, you know, it didn't show any evidence that they were using symbols in any forms. But in the last 1520 years, there's, I would say, growing evidence that they were habitually using symbols. For instance, we, you know, with with some colleagues, we publish a number of claws from raptors, these club shows cut marks on them, and these clubs would not have been an edible. So we think that they were probably used as some form of on earning mentation. And that's interesting, because claws, you know, for instance, wolves have claws bears out claws to get they use only raptors and not a very specific range of raptors, the big ones like vultures and eagles. And so it's hard to escape the conclusion that this as the this has no symbolic reason behind it. So as I saw, so

Nick Jikomes 34:37

enough, enough of those artifacts exists where you see the wrapper clause, the clause from birds of prey showing up over and over again, but you don't see see it from other creatures.

Eugene Morin 34:47

Exactly. So it's it's a combination of evidence here. The fact that these it's always large raptors, there are not many it may be one per site. You know, now we have probably 30 Lights and in Europe showing the these this use of rafter claws. And what's interesting is that, as I said, large rat, and it excludes the other form of claws from other animals. As I say carnivores or, or herbivores, the claws are not used for saying purposes. So for this reason, it's probably link in at least in my opinion, it has some form of symbolic use.

Nick Jikomes 35:27

What about other cultural artifacts from Neandertal sites? Do you see clothing? Do you see beads?

Eugene Morin 35:35

Returning to the question of symbolic use. So what's very well known and has been known for a while is that they're using pigments and mineral pigments like Hawker manganese. And so it's, it's this is a little bit more, I would say, difficult to interpret, because some people think this guy could be related to non symbolic use. That is, for instance, some people think it might be for cleaning skin, for instance, and other purposes. But I think it's, there's some evidence, for instance, in Iberia, where pigments are associated with some bone tools made by Neanderthals. And so it could have been used for decoration, you know, or body or argumentation. There's also some cave art now, that is stuck to date from the period that was occupied by Neanderthals. So we would have near the cave art. Again, these are hand stencils, or dots on cave walls. And these data about 50,000 years ago, in a pier that would only been occupied by narratives, although this has also been challenged recently. There are some people think there's some modern human incursion in the Upper Paleolithic, sorry, in the middle of Pacific, in, in, in France and Iberia. But that's quite, that's quite controversial, in

Nick Jikomes 36:58

terms of these cultural artifacts that are tied or potentially tied to Neanderthals, do we know is there any strong evidence that these were Neandertal inventions? They came up with these things independently? Or is it possible that they acquired them from coming into contact with homosapiens, or vice versa, that we acquired maybe some things that yeah,

Eugene Morin 37:20

for the Raptor clause, as far as I know, this is something this is a feature we only see in their tools. Pigments are found, you know, from basically from France to South Africa. So this seems to be, you know, widely spread trait for cave art. The cave art, we see very early cave art in Southeast Asia, probably around 45 to 50,000 years ago. So this would be linked probably to modern humans. But again, this this is, you know, unclear. So right now, a few lines of evidence that is only limited to needles or modern humans. But we, for instance, modern humans early on, by 50 60,000 years ago, they're using an even before that they're using body shells, you know, shells that are found on the beach. And these sometimes have natural perforations. And they're used possibly as necklaces. These are not found in near atolls, as far as I know. So there's some differences like that. But that's to be expected, because we have some regional variation. I think the point here is that what whether it's shell or Claus is not important. What is important is the fact that both are some form of symbolic, and they're present in both population.

Nick Jikomes 38:50

And when approximately, when did Neandertals disappear? When were they gone? For? Sure?

Eugene Morin 38:56

Well, that's that would have been about 30 to 40,000 years ago. That's about the dates we have new even, yeah. So for you 35,000 years ago, that's where last year it's all those that are genetically, sorry. Anatomically identified as has never thought these are the last ones we find.

Nick Jikomes 39:17

Are there any Neandertal burial sites where there are indications that they buried their dead on purpose?

Eugene Morin 39:23

Of course, that's an important line that I forgot to mention. So they're, in fact, Neanderthals are some of the earliest Neanderthals that we found in 1908 and are from burials from instance. Lafayette, I see or less Schopenhauer say, these are our burials. There has been some debate about whether they are true burials but for people like me work on on font ah, this does not seem very convincing, because when you look at the font of the font is shattered. You know, we never find refits between you know, we own We find sometimes a wrist that complete wrist or a complete four leg, but that's very rare. And so when we see these complete, fully articulated, you know, tall individuals, for us that it's clear, it's related to intentional burial. Some people have argued that this has no symbolic purpose. That's possible. But I think that's, in some way, some kind of double standards, because if it was a modern human being buried in that position, nobody would question that that has symbolic meaning attached to it.

Nick Jikomes 40:34

How has so I mean, I think we've already hinted at this to some extent, but how has our picture of Neanderthals and how sophisticated they were changed over the past few decades? And how does that relate to any potential biases we might have as humans wanting to think that our lineage is special?

Eugene Morin 40:51

Yeah, you know, I've always been, well, we still say, you know, my brother looked like the neurotypical or so we still have this Neanderthal or somewhat, you know, retarded, or, you know, you know, backward and so on. So, I would say the last 50 years has been to push the boundaries above their cognitive abilities. Like, you know, in the 80s, there was a much debate about whether they could speak. Now we see there, if they're able to, you know, express, you know, some form of symbolism. So, we have moved a lot, we have moved a lot, a lot of the, the arguments that have been put forward to show that they could not survive, have not fared well over the years. And so that's why people like me, would would emphasize rather, environmental factors to explain they're very extinction rather than some cultural ones. It

Nick Jikomes 41:52

sounds based on what you told me before, like, it wasn't like modern humans in the intertitles met, and then Neanderthals very quickly disappeared. It sounds like it was a pretty gradual process. And you have smaller and smaller pockets of Neanderthals persisting near homosapiens for 10s of 1000s of years, and they just sort of gradually fade away. Is that more accurate?

Eugene Morin 42:14

Yeah, I would say that's variable regionally. For instance, in areas clearly the both populations seem to have coexisted for long periods of time. But in other regions, for instance, if you go to Western Europe, at least at the geological scale, this was fairly quick. So or Russia, for instance. So it depends where you are. And that's why it makes it felt a bit difficult to make general a to to look for a general factor to explain the disappearance of Neanderthals because they are variable. So live in Liberia, at the probably a life where there was quite different from those who live in the Near East, for instance. Yeah,

Nick Jikomes 42:54

and I think that makes sense. Because even among modern human populations that I've discussed with others on the podcast, which depends on the region, sometimes two groups come together, they mix a lot, sometimes one group wipes the other one out very, very quickly. Sometimes they sort of live in close proximity, but effectively in separate niches, and they don't really interact that much. And it probably just really depends on where you look on the globe.

Eugene Morin 43:19

Yeah, I think the real challenge is that if we had only the archaeology, we would not see two species or two semi species. When we look at the physical evidence or skeletal evidence, we seem to see, you know, different populations. And that's why it's hard to reconcile the two, you know, based on the cultural fat, the cultural aspect, they don't look that dissimilar, but the skeletal, you know, especially, is tell us that they're, you know, you can you can easily not easily but you can segregate the two population based on their features. And so the challenge has been trying to reconcile these two lines of evidence that conflict, you know, on two important aspects. By

Nick Jikomes 44:02

the time you get to the late Paleolithic, if you just look at the bones of Homo sapiens, and you compare them to modern humans today, are we more or less phenotypically identical to humans from the late Paleolithic, or are there distinctions between us now?

Eugene Morin 44:22

I'm not a specialist on this question. But I would say, based on my knowledge, that distinctions are not different. That being said, we know from a genetic perspective, that there are some important distinctions. For instance, you know, tolerance to lactose, you know, this is a recent trait, it was evolved at least twice in Europe in Africa, if I remember correctly, and this occurred then less than six or 7000 years ago. So you know, there we know our genetically speaking that some of these features are very recent. They don't show up in our skeleton, but Are there?

Nick Jikomes 45:03

And so what? Are there any major? So when humans left Africa, Homo sapiens, you know, some of them went east, some of them went west, they went to all different parts of the globe. Were there any? How much divergence was there in terms of physical adaptations related to things like diet and hunting strategies? Did it very heavily region to region? Or are there a lot of similarities?

Eugene Morin 45:30

Well, I would say it has to, because if you're in Southeast Asia, you know, the range of species you can hunt is very different. The plants are different to what we know, for instance, in Southeast Asia, there is evidence for fishing that is quite early, why 45,000 years ago, we have also evidence they're using some trees grills, which probably required some farmers projectiles, maybe blow pipe, stuff like that. So some of this occurs very early in the region. Whereas if you look in France, for instance, at the same time, they're basically just hunting large gain. So there's quite a bit of variation. You know, when you compare different regions, and that's, that's to be expected.

Nick Jikomes 46:16

And so in the work that you've done, related to ethnography and looking at hunter gatherer, hunter gatherer tribes from more recent times, is there anything that studying recent hunter gatherers tells us about the hunting strategies and things of ancient humans in terms of, you know, when you think about the adaptations you spoke about earlier, or our high stamina, our ability to sweat, like where we were rerunning down game, like running miles and miles, and being persistence hunting, what do we what do we really think that hunting actually looked like that was unlocked by some of those adaptations?

Eugene Morin 46:54

Well, that's a good point. First, what we learn is that many, many archaeologists, and many ethnographers tend to think that recent ethnographer, your sort of recent hunter gatherers, are more or less are, I would say, tend to perceive them as being relatively static, that is not having changed much in the last century or two centuries. Whereas, and of course, that's here, I'm exaggerating a bit. But when we turn to had no history, so that is, to the records left by people before the emergence of ethnography as a field, which occurred in the 1850s, to or under, you know, year 1900, what we see are sometimes quite different pictures. Because people tend to forget the impact of colonization, it had a huge impact on Native population, versus led to decline in pre densities. That is, that was, you know, if you read some G Suites, or missionaries or travelers, they will all tell you that in the 19th century, in Africa, there's a big decline in the number of large game that is being encountered. If you're in Europe, or in North America, you will see similar picture where people say, since the Europeans came, we see fewer and fewer animals. Other introductions were really important, the horse in North America completely to change, the story completely changed our way of acquiring bison. It also changed the way pronghorn antelope were acquired. In other regions, the impact was probably less important, for instance, in the north, you know, horses are not as useful in the Arctic. So in this case, there was the the impact could have been smaller, but then there are other aspects that were very detrimental or at least had a significant impact. For instance, the introduction of firearms, you know, especially the repeat repeating rifle the early firearms contrary to what people think, are the firearms good, they were really bad, you know, they would explode the accuracy was low they were noisy as a native we're not really fond of early guns in fact, when we read about you know, let's say 18th century accounts, the native still use bow and prefer the bow and arrow because you know, it's more accurate and less noisy because with a bow and arrow you can shoot five deer one after the other, but you know, with with a rifle, you can only kill one because animals sleep, okay. So always created by the you know, by the impact will will scare the herd away. So that's so these things in combination means that the native habitat, the ecology has changed significantly. So Since the or the arrival of Europeans in North America and Africa,

Nick Jikomes 50:03

yeah, it sounds like what you're saying is, you know, we can't just, you know, hunter gatherer populations have changed for many reasons, in the past few centuries for all, you know, all the reasons that you mentioned. And therefore, we can't just look at recent hunter gatherers, and assume that they're a good proxy for ancient hunter gatherer. Yeah,

Eugene Morin 50:20

and here, as I said, I've exaggerated that, you know, archaeologists, ethnographers, they're, they're not naive, they know, things have changed. But I think the amount of changes on the estimated okay with with these, with the expansion of Westerners into Africa, Asia, and North America and South America, and, and also, because these are the best models, we have the, we have so much data that at some point, we you know, we forget that there are a lot of blind spots in our study. And therefore, like the some were extremely influential, like the study of the sun, or the sun, the study of the hodza, or the actually in South America, so these population became proxies. And, in some ways, by maybe be because they were the only good models we have, they became the, you know, you know, the proxies for the public. But when you go back in time, using that no historical record, sometimes you see things that, you know, are now lost. And the entrance pursuit of large game is a good example, until the 80s. This was not mentioned at all. And then David carrier came up with this model of, you know, he noted that there were some important differences in physiology between mammals and humans. And he suggested that this might be related to insurance hunting. And when we started to work on this, my colleague, Bruce winter older and I, this method was described as being marginal, anecdotal, it was described as costly. And in fact, when we, when we started to dig in depth, no historical literature, we started to find examples of endurance pursuit all over the world, not, you know, just in arid open environment that was, but we found it in the tundra, we found it in the boreal forest, in the mountains of Hawaii, we found it, you know, the tropical settings of Southeast Asia, in South America. So it became a common method. And when I say common, I don't mean, that was practiced daily. But it was something that was habitually practice, in certain contexts, for instance, when there's a lot of snow, or when the weather is very hot. And so that's an example of a technique that became obsolete when the rifles was introduced.

Nick Jikomes 52:57

I see. Yeah, it makes sense to me that endurance hunting in particular would have been relatively common in our species, because of the adaptations you spoke about before the our ability to sweat and the changes to our muscle fibers, because in the absence of those adaptations, hunting is still possible, right? Humans could have quietly crept through the woods and use camouflage to engage in hunting, but the endurance hunting aspect seems to be what those adaptations really unlocked.

Eugene Morin 53:22

Yes, and it so it's probably related to the context of hunting. But what's important also to notice about endurance pursuits, is that they have a higher success rate than other methods, then many other methods, because you exhaust the animal, the animal still does not have many options when it's getting very tired and overheated, whereas an animal you're crept it, you know, creeping on, while the animal, you know, often you cannot, you know, keep in mind that these, these games have evolved and CO evolved with humans for a long time. Yeah, so their sense of smell is highly developed. They, their sense of hearing too, is well developed. So, it makes it very hard to creep, and come close to, to an animal like, for instance, a good example is moose. You know, when you read about news, people will say, it's extremely difficult to get close, or even to view, you know, to see a moose most often, the animal will have vanish away before you see it. And so just to rebound on this, and many people describe insurance, hunting, we'll say that you run after an animal you don't see you try to predict where the animal is going. And sometimes you will, you know, at some point, you will succeed in catching up with the animal, the animal will be scared away, and bounce and you know, leave again, and then you catch up again, and so on. And it's this repeating cycle of sprint and rest But that leads to the procurement or at least to success. Okay? So and it's again, it's the buildup of feet that allow us to to overtake these games and other methods, either snaring, spearing, ambush, all these methods are assessed with a lot of failures.

Nick Jikomes 55:23

Yeah, that makes sense. I'm not sure if this is your area of expertise. But as you leave the Paleolithic, and you get to the period of time when agriculture is developing, when people first started developing agriculture and becoming sedentary, did this lead to any phenotypic changes based on how their diet was changing? Because I've heard before, things like, you know, at the dawn of agriculture, skeleton start to become less robust. There are changes in bone density and teeth that have to do with eating different foods. Can you speak a little bit about what we might know there? Yeah. So

Eugene Morin 55:59

what we what we see at least in terms of the skeleton, yeah, there's some of these more cavities associated with the, you know, a greater intake of plants, the skeleton is more or less robust, probably because they're running less they're, you know, ranging less also. In terms of the brain, we don't, as far as I know, there is no difference in but there's probably also some genetic evidence that there's selection for greater tolerance to certain toxin. As I said before, lactose intolerance, you know, that's something a feature we see in many humans. This, you know, with agriculture, often you have domestication of animals, with the domestication of animals. Yep. Milking. And when you have milking, well, some people don't tolerate milk well. And so there was probably selection for or, you know, people can tolerate lactose, lactose better. And so all these things are indicating there are still significant changes occurring at the genetic level. At the skeletal level there, the changes are more modest. At the geological scale, of course.

Nick Jikomes 57:20

What like, when you when you look at humans can modern humans our lineage in comparison to the now extinct the many forms of now extinct? Species of homo? What What are like some of the salient differences that you think, explain why our species persisted? And these other ones declined all over the world? Does it have a lot to do with our symbolic cognition and our big brains and our ability to have in general culture doesn't have a lot to do with our ability to adapt to physical environments and our local motor capabilities and things like that? Or is it not so clear cut?

Eugene Morin 57:57

Well, one aspect that is very clear, to me, is the importance of socialization. When you look at other species, you don't see for instance, sharing much other than between offspring and mothers. But in humans, you see humans giving food to a non kin, which is very unusual in mammals. And I think so that's probably one of the key features of our lineage is this, you know, selection for increased socialization, increased cooperation. This is something again, that is not seen in, in Ma'am, you know, is rare and other mammals you will see it, you know, are animals that are Greek areas to some extent, but not to the extent we see it in humans?

Nick Jikomes 58:48

And do you think that relates at all to how our diet and our procurement of food have evolved over time? So for example, I could imagine, I mean, if you want to go hunt big game, you can do that in a solitary way, I suppose. But I imagined that a lot of a lot of those sounds probably require coordination between individuals. If you want to scavenge a big kill from apex predators, I would think that probably necessitates a group that really coordinates between each other and uses language, and is able to move and use tools very quickly. Do we know anything about the relationship between the ability to cooperate in order to get food either from hunting or scavenging as being maybe part of the basis for our our cooperative abilities more generally? Yes,

Eugene Morin 59:34

I think we can definitely say that procurement of food. The the the aspect of cooperating is very important, but not just with animals. For instance, with plants, it's very important to transmit 10 transmit the import, sorry to transmit the information about plant phonology. For instance, if you are moving around the landscape, you know, you need to know where plants are First, but also in what state? You know, do do the flowers or the, you know, where are the patches? How can you detect, where, for instance, if you're looking for tubers you want to know, the they are which month are likely to be edible and so on. So this is in the very important aspects. And now with respect to animals, well, you know, if someone sees tracks of animals, because when you read the ethnographic record, there had no surgical literature, often people will say, what's very critical is that that was informed there were trucks over there. And so a men will tell that his wife told him to look for Steam Box and that region or for gemsbok, or for caribou. So that's when you're you have individual hunting, but a form of hunting that has been very important before, let's say 1900, was coming out hunting, and we just published a paper on it, actually, it's still under, not under review, but it's still being it's in press right now. And in this paper was stressed the importance of coming out hunting as another form of hunting that was impacted by Western Westerners and, you know, sort of, above Westerners in coming in to Eurasia and so on a story about Africa and South America, and so on. And so in this paper, we stress that this is a locus for selection, probably because, you know, with with, with Colonel hunting, you increase also the, the odds of success, because you by using a lot of beaters, and by driving them toward a special locus, you can have Spears away there. And you know, these hunts tend to have high returns, especially if you're hunting gregarious species, like bison, or caribou, some of them, you know, will result in large quantities of meat being acquired. But then this creates a collective action problem. How to you distribute this meat? Who gets apart? Is it only the person who have hunted? Is it the person that we're meeting those who did not collaborate? Or could not collaborate? Do they get the share? So these crates, you know, very important problems, where socialization becomes a key. And so I think that might have been a key, I think, in terms of devotion of socialization in humans, I mean, these kinds of settings.

Nick Jikomes 1:02:38

And, you know, given how much diets vary regionally and across time even before the dawn of agriculture, right you know, people living different parts of the world would have been eating vastly different things just based on the local flora and fauna that that was in their habitat. Given that diversity doesn't make a lot of sense to you when people today talk about things like the Paleolithic diet.

Eugene Morin 1:03:00

For for archaeologists, this is a nonsense This is pure nonsense. There is no pelo thick diet there pelo diets plural. And because this is not possible, when you look at the diversity, I mean, it would be in terms of selection, they would be crazy to have a pelo diet, because in some regions, you know, plants are not available during you know, two thirds of the year. In other regions. Large game is not abundant. In other regions, what you have are marsupial's rather than an placental mammals. So you have to adapt and you know, to the environment, and that creates the cause for flexibility. That's what we see in humans variability, flexibility. So the pelo diet is nonsense to archaeologists.

Nick Jikomes 1:03:53

And when you so one of the key physical adaptations we talked about, was, you know, aspects of the body that enable physical stamina, and that unlock the ability to do things like endurance hunting, as we were talking about. This also presumably created a selection pressure for mental stamina. We had to, you know, focus on a problem for extended periods of time. So do you think those two things evolved hand in hand the ability for physical stamina on the one hand, and our attentional capacities our ability to sustain attention on the other?

Eugene Morin 1:04:25

That's an excellent question. I think, you know, I found an excerpt about about STEM mental stamina, maybe just a month ago was really interesting because the guy was saying, we have in our group I think he was a Nash, Nabil or someone from the boreal forests in Canada, around the Hudson Bay, and it was saying basically, we have you know, in a paraphrase basically said we have something about mental toughness that is being transmitted between you know, now We're a group, and we tell each other and we, you know, tell the kids how it's important to, you know, keep on running and running and running, and not give up because the animal will give up before you and so on. So there's part of it, that's probably cultural, whether it's also genetic, that's, you know, that's a topic that would be a bit more difficult to evaluate. But clearly, there's, there's something about, about Ultra trans cultural transmission, that is important. And one thing we have to keep in mind too, is that running, it has other important evolutionary implications. Keep in mind that, you know, in a politic past, what we have, are groups that are, you know, competing for resources. So warfare, and in the context of warfare, running is key. So we see, you know, even if our sample of running pursuits just show, basically, the presence of males, females are poorly represented in our sample, maybe four or 5%. We have a lot of evidence that women are running in, you know, and training for running. And we have a, you know, examples where dads are telling their daughters, you know, you have to know how to run, because it might save your life, you know. And so, this, this aspect is also critical to keep in mind when we address this problem.

Nick Jikomes 1:06:32

And as you know, does the Archaea is the archaeological record rich enough that we can see, as humans were spreading across the globe? You know, we're hunting animals of different types. How, how sensitive were humans as they were migrating to the maintenance of animal populations? They were interested in hunting? Are there any instances, pre pre colonialization? Before, you know, modern technology before guns and those things would peep would people move into a region and just sort of hunt everything until it was gone? Did that happen? Sometimes, were they able to figure out how to hunt enough to feed themselves but not so much they deplete local populations? Or did ancient humans drive a lot of animals to extinction through hunting?

Eugene Morin 1:07:19

That's an interesting debate. What we see, we have to think a little bit about how the native see these things. First, natives are incredibly knowledgeable about animals. It's just astonishing the amount of information didn't know, one aspect that is harder for them to evaluate is the mytab population level. For instance, if you hunt caribou, and you live in the region, let's say close to the Hudson Bay, it's really hard for you to know how the population is doing on the scale of a continent. And so your decision will be off course based on your local knowledge. And so when you ask about, you know, when you ask natives, or at least when you read about natives, what they say, often they say, if you kill an animal, the animal is not really dead. It's sold if you behave in a respectful way, and if you do the proper ritual, the animal will actually go and or the soul of the animal will go, and we'll create a new animal. And in fact, the animal will come back. And they say that about fish, for instance, you're saying, If you treat fish with respect, you know, the fish will come back, I even found an example where the guy says, I made a mark on the bone, just to make sure. And then later on, I found in another animal of that species, and I found that St. Mark, so the animal came back. And so when you have this kind of thinking, then you don't have the idea that then species can become extinct. Because if you are spiritually and ritually taking care of the animal, the animal will come back. And so when we and some studies have been done some ethnographic studies that have been conducted, and the natives are not trying to minimize their intake of females or you know, of juveniles, they just kill what they need. So, and I would say that makes sense. Because if they have been doing it for, you know, millennia, why would you change your method, you know, why would you start to focus on certain game, and for those who do ecology, in fact, if you kill a lot of animals, you reduce pressure on those who survive, and those who survive will often do better. And so they come back. So extinction is a very difficult concept, until you have some metapopulation data. In fact, until you know, the early 20th century, we didn't have a really good idea of extinction. You know, it was a topic that was really hard to address, because we have poor data. And so to make a story short, extinction is not something that people worried about when they hunt, because their method had a small impact on the on the game population. And also because they believe that if you are treating animals with respect, they come back.

Nick Jikomes 1:10:26

Where do you think like a lot of the a lot of those rituals and spiritual beliefs? Do you think at all about like, the purpose the sort of ecological purpose of those things for human hunter gatherers? Are those you know, are the spiritual practices and beliefs that the different tribes have? Are they epiphenomenon? Or do they serve some kind of behavioral regulation purpose that's important for survival?

Eugene Morin 1:10:49

That's a good question, too. We talk all you know, there's a lot of talk about sympathetic magic, you can imagine, if you are, you know, living in a boreal environment where you know, it's cold during six months, there are no plant. So, you know, game procurement is critical. One way to reduce stress is to use rituals, you know, and, you know, to reduce ambiguity about, you know, procurement. So these ritual often have this purpose of trying to help, you know, and secure success in the future. So there's some, I would say, maybe evolutionary aspect in that respect. So it's cultural, but it has some evolutionary implications still. So I don't, you know, I will not dwell too much on that. But it's interesting to keep in mind that these things are there, because there's some stress and in the first place, what,

Nick Jikomes 1:11:47

so So over the course of your career, in your own understanding of Paleolithic humans, and the evolution of our lineage, what's something that has, what's an example of something where your viewpoint has changed, or the field has really come to a different conclusion? In terms of where it's at today, compared to where we were, you know, 1020 30 years ago? Are there any major sort of 180s or, or something like that, that we've done in terms of how we think about the the evolution of early modern humans, I would

Eugene Morin 1:12:20

say that happens a lot more than you would expect, Francis it, you know, the idea that that middle politic was only occupied by Neanderthals was a, you know, a given for everybody. Now, it's being you know, thought as something to rethink about. That's a good example. And trans hunting is an example. I didn't know about this month, that method where I had, well, I shouldn't say didn't know, but I thought really, it was marginal. And so that's an example where I completely changed my mind about its importance. I remember the Hobbit, the discovery of The Hobbit in Southeast Asia, some kind of species that look like in this trope at the scene, but dating 200 to maybe 50,000 years ago, that came to a shock to everybody. Nobody thought that there was nothing that there was a species that would be that would look like an ostrich at the scene, but being sown young in age. So that's another example. Another one, and this is more of a conceptual one. For the third, let's say 30 years ago, the idea of speaking about kinship, how people relate to each other, was unthinkable when you think about the politic, there was nothing we could use to talk about kinship. But now with DNA. There's a study that has been published a few years ago, where they say Nero toes were patrilineal, which means basically, male stick together, and women migrate to other groups. This is something that we never thought we could do. I never thought this would be possible to talk about this in my lifetime. And this is a major for me a major kind of change. So some are technological discoveries. Some are, you know, are important, I would say conceptual findings, and other examples of the importance of fat. Before I started doing political research. I never thought that fat was that important. You know, like any Westerner? You mean, whether dietary fat? Yeah, we think about meat. You know, when we think about animals, we talked about meat, we always talked about meat. Whereas when you talk to, you know, a native, it's about fat. They wonder about how fat the animal is. They don't really care about the muscle. You know, another example a few years ago, I published with my colleague, John Smith, about rotten meat. You know, rotten meat is something that Western think is, you know, not edible. While we found tons of evidence that it's being eaten and some Plants are preferred by natives in the rotten state, because it makes digestion easier, and some prefer to taste. And so that's another example where rotten meat was considered a no, no. And then, you know, by doing some non historical research, you discovered that now this is a cultural construct, actually, rotten meat is palatable. And if, you know, if you're used to eating rotten meat, well, over the years, you will, you know, be able to metabolize it in, in a reliable way, and you'll be fine. And

Nick Jikomes 1:15:34

that was actually that reminds me of what we spoke about earlier, where we talked about the fact that humans like other like certain other animals will say, you know, those vultures that scavenge a lot of meat, eat a lot of, you know, rancid or partially rancid meat, they have very low, very acidic stomach pH. Is it possible that, you know, this is something that goes way back? Humans were scavenging meat to some extent for a long time? And it's actually it's actually a modern aberration that we think of? Yeah.

Eugene Morin 1:16:02

Yeah, what's striking, and when I say rotten meat, I don't mean like high meat. I mean, like meat full of maggots, like really, really transformed. Okay, really, you know, run, not just, and some groups, we have examples of an excellent example, during the Franklin Expedition, you know, when they were trying to find a Northwest Passage, there's an inward guy will come to a boat to the boat of the Franklin Expedition. And he comes with a seal full of maggots, stinking like crazy. And the guy said, you know, it comes, you know, so he's holding that seal. And the guy said, There's no way you're going to put that on the boat. And the the innovators pissed, because for him, it's like, he found a breed, you know, or, you know, a green cheese and camo bow,

Nick Jikomes 1:16:55

he was excited beings,

Eugene Morin 1:16:56

he's being told to get rid of it. And for him, it makes no sense. You know? So that's, that's an another example of, of where, you know, encountering other people's view, make you think your own, you know, make you rethink your own views. Wow.

Nick Jikomes 1:17:14

rotten meat? Yeah, I mean, I guess, I mean, if I stopped, I mean, obviously, it's, it's not what I'm used to. It doesn't sound appetizing to me. But when you start to think about hunter gatherers, and you know, living out in the wild as an ancient human, you know, if there's magnets, the magnets have protein, maybe they've pre digested some of the, some of the mid food material, and it's actually easier if it's eaten raw, if you can't cook it, or things like that. So that's interesting.

Eugene Morin 1:17:39

Yeah, so, you know, throwing out the mystery. It's your you're colliding with others view all the time. And some are trivial, but the others are quite spectacular. And

Nick Jikomes 1:17:53

are there any other way? I mean, are there any other aspects as like an ethnographer, and a pillar anthropologist, like everything that you've studied? Are there any, what are some things today that we take for granted that we think are normal that like you think most hunter gatherers would probably find very bizarre? I mean, besides the obvious, obviously, they wouldn't know what an iPad is. But in terms of something that's maybe more of an everyday thing, do we also do weird things that would be seen seem very weird to them? Well,

Eugene Morin 1:18:19

simple things like, you know, we have three meals a day. There's no that's culturally constructed, you know, some groups eat twice some, some eat all a bit all the day, you know, alter the day, some will have a big meal in the morning and a lighter one. So it's highly variable. So the idea that we have a lunch at six together as a family, that would probably be strange to many people. Well, maybe the obsession about hygiene. Okay, when you read about natives, what the what you see is that they say it's stinky, dirty and everything. And we have example, for instance, a beautiful quote, We found where a woman has a child on her, and she's cutting meat, the baby poo on her, she used the knife to scrape off the the excrement, and she continued continue cutting the meat, you know, that's the level of hygiene. If you're used to that, and you live like that. It's not the you don't think about that. But the idea here that, you know, you must have perfectly sterile toilets and stuff like that, that would be so foreign to Native people who have not met Westerners before.

Nick Jikomes 1:19:42

Does your study of humans and human evolution in particular, you know, things like diet and our ability to adapt and be flexible and the things they eat? Does that influence how you think about what you eat today in our in our suit environment?

Eugene Morin 1:19:57

Yes, completely. Like the, you know, above the high beat, for instance, I'm less concerned that I should be, I guess. So that's an example. A lot of things you just realize, okay, that's, that's this is a customer cultural construct. I'm not saying it's, it necessarily changes the way I do things on a daily basis. But it also clearly opens the mind about how you view things. And, and it makes you understand also why people behave in a certain way. Like I said, about the, when I was talking about the collective action problems, you better understand why people why it's so hard, for instance, to prevent people from hunting species that are, you know, that are close to extinction, it's very hard, because you require some kind of knowledge about the meta population that nobody has, you know, you require scientists to collect information for you and tell you this is how it's going, you know, for that species, but, you know, on the regular empirical basis, you know, observation basis by people, there's no way to know, other than say, it seems that they were more of that animal before then the now but that's it. You know, what,

Nick Jikomes 1:21:12

I'm in your research today, right now, what are some of the questions that you're thinking about and working on today?

Eugene Morin 1:21:18

Well, right now I'm working on the first I'm working on the monograph on hunting, I tried to whether we want it or not, when we think about the pelvic cloak, you know, very quickly, we come to the idea of spears, and individual hunters. But, you know, they have no history and ethnography made me realize, there's way more to hunting than just a single method. And now I realize that hunting is probably, in fact, our range of different methods that are used in different contexts. You know, in our society, a hunter is a guy with a gun, probably waiting in a shelter, something for an animal to show up, okay, that's, that's painting our way of looking at hunting. Whereas, you know, for native, it's really a range of methods that when you are in situation A, you use method one, and in situation b, you use method B, method two, and so on. So that's what I, you know, I'm concerned with right now strike to an hour, in other words, to enrich, or at least rethink our models of hunting.

Nick Jikomes 1:22:28

Are there any final thoughts you want to leave people with with respect to human evolution, how you think about it, or maybe, you know, maybe a good takeaway that you think people should have when they think about our own species and where it came from?

Eugene Morin 1:22:42

Well, I would say, first, we underestimate how things have changed in the recent past. Okay? When you look at foragers, today, there are tiny portion of the variability that existed, let's in 1500, there's so much more to learn from these, you know, these travelers, these these G's, woods, these missionaries that were traveling through the so called Wild, you know, countries, so there's a much much to learn. So, you know, the past was probably way more varied than people think. And, you know, a lot of models are simplistic, they assume, you know, one population moving out replacing another, I think life is way more complicated than that. And as a result, you know, what we need is better richer models that are used, that are based on ethnographic observation at no historical observation.

Nick Jikomes 1:23:44

All right. Eugene Morin, thank you for your time. That was fascinating. A lot of cool stuff. I think you do really interesting research and I had a lot of fun. Looking at some of it in the last couple of days and thank you so much.