At Darwin's time, nothing was known about genes. Darwin and others only knew from observations in the world that there is a lot of variation between and within speices, and that offspring resembled their parents. Characteristics are inherited in some way to offspring, and new variation come into the world somehow. So Darwin formulated his theory of evolution by natural selection very general and without reference to a specific inheritance mechanism or a specific thing that carried the information about traits. Through the work of Gregor Mendel and with the discovery of the DNA, biologists were sure that they had now found the structure that encoded the information about traits and the mechanism that allows the inheritance of traits (reproduction and inheritance of DNA to offsrping). Thus, the theory of evolution was rewritten in the 1940s as "a change in allele frequencies in populations." This formulation of evolutionary theory is called "Modern Synthesis".
But in recent decades, many biologists have noticed that inheritance of genes can not alone explain all the traits that we observe in living things. For example, many animals appear to "inherit" behaviors to offspring and others by imitation. Also, many animals seem to "inherit" or pass on structures created by them to their offspring, which have an influence on their chances of survival and reproduction.
Especially in the field of human evolution, it seems that we must consider these other modes of inheritance: humans have many cultural traits and technologies that have no genetic basis (or: the variation in cultural traits we see in the world does not correspond to a variation in genotypes), and yet these traits vary and are transmitted to others in a population, even selectively (some traits are transmitted more than others).
So many biologists suggested that we need to expand the definition of evolutionary theory to explain the variation, selection and transmission of phenotypic traits and things that are not very tightly linked to genes and to generation change. Cultural evolution, i.e. the changes and distributions of behaviors, beliefs, norms, knowledge, technologies, worldviews, institutions, and other cultural traits in populations, can be studied and explained with the help of this extended theory of evolution.
Comparing gene-focused approaches and phenotype-focused approaches to evolution
(incl. cultural phenotypes)
What changes in the population are focused on?
The frequency and distribution of genes / alleles involved in the expression of a trait
The frequency and distribution of traits, including genes, body features, brain features, behaviors (including cognition, beliefs, values, language), social organization (including norms, institutions, group structures), technologies and structures created by living things
What are the causes of new variation in the trait?
Random mutations and recombination of genes
Different possible mechanisms depending on the trait: genetic mutations and recombination; trial-and-error, recombination of ideas, coincidences, innovativeness; behavioral response to changing environmental conditions
How does the "selection" of traits occur?
The trait increases the chances of reproduction under the given environmental conditions.
Depending on the trait: enhanced reproductive success; conditioning, learning or inner preferences motivate individuals (consciously or unconsciously) to learn, imitate, rebuild, use, or teach others (sometimes called cultural selection)
How is the trait inherited or transmitted within the environment?
Through biological reproduction and inheritance of genetic material to offspring
Different possible mechanisms depending on the trait: inheritance of genes; social learning (including imitation), teaching; accumulation of created things and structures that persist in the environment over time
What is the meaning of the term "fitness"?
Number of surviving offspring; the increasing frequency of the gene/allele in the population
Depending on the trait: number of surviving offspring; number of imitators; stability or persistence of a trait, the increasing frequency of the trait or thing in the population
Can living beings adapt to environmental conditions in the course of a lifetime?
No, because the genome in the germ cells of an organism does not change in the course of a lifetime. Only populations can adapt.
Yes, because many organisms can change their behavior or their environment, or create new things.
Some biologists consider organisms themselves as populations of cells and trait variants, which "evolve" over their lifetime through different mechanisms.
Where is information stored?
In genomes, brains/neural networks, social networks, and the environment (structures, technologies, books, internet...)
The beginnings of our cultural evolution (traits: technologies)
3 - 2.5 Mio years ago: first Oldowan stone tools and the beginning of the stone age. The making of these tools already required a higher patience, ability to plan a few steps ahead, better control and coordintaion of hand movements, compared to the tool making observed among chimpanzees (see First stone tools)
1.7 Mio years ago
The hand axe as the next innovation of stone tools. The quality and variation of the hand axes increased steadily from this point onwards. The length of time and steps between identifying a problem ("finding food") and solving it have become longer - tools were increasinlgy manufactured for the future, and transported across more distances, which required increased cognitive abilities. The passing on of this technology also required increased skills for social learning and teaching.
Reflection: Between the appearance of the first Oldowan stone tools and the emergence of the first hand ax, about 1 million years have past! What could be the reasons why there did not seem to be any far-reaching innovations in tool making in the populations of our ancestors over such a long period of time?
About 1 million years ago: First signs of the use of fire. Fire allowed, among others, greater protection against predators, especially at night.
About 800,000 years ago, Homo erectus was apparently able to control fire. Processing meat with the help of fire made it easier to chew and digest, making meat-based energy more efficient, improving the food supply to the group, and further reducing selection pressure on the physical "chewing tools" of the body and digestive organs.
Use of fire certainly also had an impact on social life - sitting together by the fire, showing each other things, and eventually telling stories of the past and future.
Ca. 400 000 years old spear from Schöningen, Germany.
Starting ca. 300 000 years ago
Tools of the middle stone age
Tools from many different materials (stone, wood, bone), for many different purposes, including for processing many other materials
- Richerson, P. J., & Boyd, R. T. (2005). Not by Genes Alone. How Culture Transformed Human Evolution. Chicago, USA: University of Chicago Press.
- Laland, K. N., Uller, T., Feldman, M. W., Sterelny, K., Müller, G. B., Moczek, A. P., … Odling-Smee, J. (2015). The extended evolutionary synthesis: its structure, assumptions and predictions. Proc. R. Soc. B, 282(1813), 20151019. https://doi.org/10.1098/rspb.2015.1019
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- Mesoudi, A. (2011). Cultural Evolution: How Darwinian Theory Can Explain Human Culture and Synthesize the Social Sciences. Chicago, USA: University of Chicago Press.