Teleology and Inheritance of Acquired Characteristics

Tunicates are supposed to be the first creatures to develop a notochord and are thus thought to be the distant ancestors of all creatures that have a vertebral column - the backbone of fish, reptiles, and mammals.

These are the adult form, only about a centimeter high, attached to an old dead section of coral.

The basket inside the translucent tunic is a ribbed cage lined with cilia. The cilia whip back and forth to drive water currents through the tunic, entering one end of the basket and exiting through the large hole.

Microscopic plants and animals get trapped on the mucous lining the basket's ribs and are moved by ciliary action into the digestive tract.

Young tunicates are wiggly tadpole like creatures, propelling themselves through Sea by wagging their famous notochords.

If evolutionary biologists are correct, their soft, flexible, cartilaginous notochord ties their thread of awareness to fish, reptiles, mammals and to us.

Tunicates are aware of their surroundings and their active young even more so as they must avoid predators while swimming in the open sea and somehow locate a good spot on the reef to settle down and become sedentary.

But they are nowhere near as clever as their more distant children, like fish or us.

Teleology

The idea that creatures evolve their perfect and wildly imaginative forms for a predesigned reason is called teleology.

Teleology is thought to be easily disproved and has been relegated again and again to the dustbins of dumb ideas.

Fish did not, for example, hold a committee meeting and decide to grow fins so that they could swim.

The Inheritance of Acquired Characteristics

A second, related idea about evolution was introduced by Jean Baptiste Lamarck in 1806. He believed physical (or mental) characteristics acquired during a creature's life could be passed one generation to the next. Back then nobody liked the idea of evolution at all and they were quick to disprove Lamarck with the snide but convincing argument that no uncircumcised male humans were born and foreskins have not even gotten shorter despite several thousands of years of lopping them off at birth.

In a way, both these debunked and ridiculed ideas are correct if you consider populations rather than individuals. Little boys may not be born without foreskins but they don't keep them long. And they lose them for a reason - to cull out hemophiliacs. Humans are special cases, we all agree. No other creature cuts off parts of the sex organ to cull hemophiliacs.

Fish evolved from earlier creatures that swam to chase prey or avoid being prey. They changed their behavior patterns to meet new challenges from predators, seek new prey, attract mates or hide from enemies, live in areas of strong currents or hide in tiny caves.

The change in behavior then gave slight advantages to populations of fish with fin characteristics best suited to that kind of behavior. In any population there were some fish that, by chance, happened to have better suited fins than their siblings.

The better endowed fish had more young and the improved fin shapes became more common within that population. Thus, over a period of hundreds, perhaps thousands of generations, the fins were shaped by the fish behavior into specific shapes and uses.

Try or Die

Behavior changes always leads the process of evolutionary selection. From this viewpoint, the specialized fins of a particular species of fish did evolve for a purpose - survival of the fish within a specific envelope of relationships. The difference is that the purpose was not determined in advance, but is a pre-set condition of life that demands that organisms try very hard to survive. This is a behavioral characteristic, not a morphological one. But it is still deterministic, especially when applied to the population as a whole.

As for acquired characteristics, while the adventures of a single fish may not be passed along to its progeny, there can be no doubt that behavior patterns acquired by a population of fish do indeed get passed along to the progeny, if only by the necessity of the progeny surviving in the new habitat or condition imposed by the behavioral shift. Eventually, behavior acquired by a small population of fish can spread to become common to a species if the characteristic improves its ability to survive.

Evolution is hardly a game of blind random chance. Creatures work hard to select themselves for survival. The more inventive and clever they are, the better their chances of having more young. And if they learn how to survive in difficult surroundings, advancing some behavior pattern that gives them an edge, moving perhaps into a new domain, their young must emulate this new behavior or perish. Those that succeed best have the most young, but they have to try or they die. What's more, there are as many, if not more, creatures that survive by cooperation than there are creatures that survive because they are more aggressive.

Epigenesis = The Inheritance of Acquired Characteristics

Modern research shows some acquired traits can indeed be passed down through epigenetic mechanisms. These chemical modifications to DNA, histones, RNA, and even changes in the microbiome can influence the traits and behaviors of future generations. This fascinating interplay between our genes and environment offers new insights into how life evolves and adapts.

How Epigenetic Inheritance Works

1. DNA Methylation: Adding methyl groups (chemical tags) to DNA can turn genes on or off without changing the actual genetic code. Environmental factors like diet can cause these changes. For example, mice fed a certain diet showed changes in fur color and metabolism that were passed to their offspring.

2. Histone Modification: DNA wraps around proteins called histones, and chemical changes to these histones can affect gene activity. Stress can alter histone modifications, and these changes can influence how offspring respond to stress.

3. RNA-Mediated Inheritance: Small RNA molecules can control gene expression and can be affected by the environment. In C. elegans (a type of worm), environmental stress changed RNA molecules, which were then inherited, affecting the traits of future generations.

4. Transgenerational Epigenetic Inheritance: Changes in gene expression caused by environmental factors can be passed down for multiple generations. People who experienced the Dutch famine during World War II showed changes in gene expression that were also seen in their grandchildren, affecting their health.

5. Microbiome Influence: The microbiome consists of all the microorganisms living in and on us. This community is influenced by our lifestyle and environment, so a mother’s diet can shape her baby’s gut bacteria, impacting the child’s metabolism and immune system.

Notable Studies

People conceived during the Dutch famine of 1944-1945 had changes in DNA methylation in genes related to growth and metabolism. These changes were also seen in their children, suggesting that the effects of the famine were passed down.

Rats exposed to stress showed changes in DNA methylation in their sperm. These changes were inherited by their offspring, who had altered stress responses.

Plants exposed to drought had changes in DNA methylation that were passed to their offspring, making them more resistant to drought.

Teaching DNA new tricks

Waddington, in the 1950s, gave embryonic fruit flies a temperature shock and a small percentage of them grew wings without a characteristic cross-vein.

He selectively bred the cross-veinless flies with each other, repeating the shock, and the percentage of veinless offspring increased each generation. Eventually, his strain of fruit flies all produced offspring without cross veins. To his amazement, they continued to produce this variant even when he did not give the embryos the temperature shock. Somehow he had "taught" the genes to anticipate the temperature shock the way one might train a dog.

When a population of creatures learn a new behavior pattern, this behavior guides the selection process of all the individual creatures within the population - and often within the populations of many other creatures as well.

This does not take very long, just as it does not take long to breed a new strain of cat or dog or chicken or rose. Many evolutionary biologists talk about natural selection as a random event. They overlook the fact that selection is the key part of the process, and selection is based on anything but random chance.

Transmitting Acquired Characteristics is normal for most living creatures

Creatures that reproduce by budding or dividing actually do pass along acquired characteristics from one generation to the next. It is one reason bacteria are so effective at combating drugs.

Populations of bacteria may contain a billion individuals. When exposed to an antibiotic the entire population might be killed. Antibiotics interfere with some aspect of the information network of each individual bacterium; perhaps preventing the formation of a special protein in the lipid membrane, causing it to rupture. If, however, some or even one bacterium in the billions in the population, finds a way to overcome the chemical interference and repair its information network, it will survive. If one bacterium can survive in the presence of an antibiotic and then divide and divide again, it will pass along the learned behavior of how to survive the toxin to all of its progeny and displayed if the same antibiotic is encountered.

Recent discoveries demonstrate that many species of bacteria maintain a high level of genetic mutation - as opposed to stability - to prevent being trapped in an evolutionary dead end. Under severe stress the rate of mutation increases rapidly, in exactly the same way that people suddenly begin thinking of, and trying out, a larger array of ideas when their survival is threatened.

Cooperating for Survival

The pattern of behavior of the cells creating form and function of multicellular beings changes slowly over time.

Changes in cellular behavior requires molecular shifts just exactly the way geneticists say. But genes are memories, recorded in complex molecular relationships within bacteria or cells. And nobody is sure exactly how these changes happen under natural conditions.

Bacteria pass DNA back and forth like passing ships exchanging notes.

Protozoans also exchange DNA when not dividing by fission.

Multicellular organisms pass their DNA in a complex sex rituals.

These exchanges hasten the process of evolution by increasing diversity. But even here, behavior plays an essential role, because the DNA may alter the recipient's behavior in ways that are totally unpredictable.

A genetic message may have no meaning at all for some individuals but may, when set into a combination of other memories or environments, set off a whole new train of behavior with vast importance to the survival of that individual and all its offspring.

Epigenetic Inheritance via the Human Egg Cytoplasm and Organelles

The transmission of molecular information through the cytoplasm of the human egg, including the role of mitochondria, small RNAs, and protein modifications, provides compelling evidence for epigenetic inheritance.

1. Cytoplasmic Inheritance: The cytoplasm of the egg contains not just the genetic material in the nucleus but also a rich array of molecules, such as RNAs, proteins, and organelles, that can influence the development of the embryo. These cytoplasmic components can carry epigenetic information that affects gene expression in the offspring.

2. Mitochondria: Mitochondria, the powerhouses of the cell, have their own DNA and the Mitochondria are inherited maternally. Epigenetic changes in mitochondrial DNA, such as modifications induced by environmental factors or stress, can be passed from mother to offspring and influence traits related to metabolism and energy production.

3. RNA Molecules: Small RNAs and other non-coding RNAs present in the egg cytoplasm can regulate gene expression after fertilization. These RNA molecules can be influenced by the mother’s environment and can affect the development and health of the offspring.

4. Epigenetic Marks on Proteins: Proteins in the egg cytoplasm can carry epigenetic marks, such as those added to histones. These marks can influence the structure of chromatin (the material that makes up chromosomes) and regulate which genes are active or silent in the early stages of embryonic development.

Supporting Studies

1. Mitochondrial Epigenetics: Research has shown environmental factors can cause epigenetic changes in mitochondrial DNA. For example, maternal stress or diet can alter mitochondrial function and these changes can be transmitted to the offspring, affecting their health and disease risk.

2. Small RNAs in Inheritance: Studies in mammals have demonstrated small RNAs present in the egg can be altered by environmental factors experienced by the mother. These RNAs can influence gene expression in the embryo and can be inherited across generations.

3. Histone Modifications: Histone proteins help package DNA in the nucleus, and these carry chemical modifications that regulate gene expression. These modifications can be established in the egg and maintained after fertilization, influencing the development and traits of the offspring.

Why it matters

Epigenetic inheritance can play a role in the transmission of disease risk. For example, maternal diet, stress, and exposure to toxins can influence the epigenetic state of the egg, affecting the offspring’s risk for metabolic diseases, mental health disorders, and more.

Epigenetic mechanisms allow organisms to rapidly adapt to changing environments. This form of inheritance provides a way for acquired traits to be passed to offspring offering a survival advantage.

As a matter of fact, come to think of it, paleontologists are now fairly certain all modern human beings came from a single female ancestor who lived in Africa.

The combination of genetic memories that arranged themselves in her mother's egg were a winner.

Genetic Memory

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