Molecular genetic evolution of man

• "Genes of alcoholism" and adequate self-esteemText of the lecture

Humanity multiplied so successfully that there was not enough space in its native Africa, and people went beyond its borders, settling Asia, Europe and, crossing overland, which was instead of the current Bering Strait, to America, successfully settled there. It is assumed that almost all the currently inhabited corners of the Earth were occupied about 25-15 thousand years ago.

Thus, I immediately answered the questions about where man originated – in Africa, when he arose, and I can immediately say how he arose: he turned out to be a monkey by natural selection, but it was not a modern monkey, but a common ancestor of man and other living higher primates. Now all the most impatient can relax, have a beer, because you have already heard all the main things, and until the end of the lecture I will present the details of this story.

Before considering in more detail the various aspects of human evolution, I will try to highlight some more questions. From the point of view of geneticists, as well as some colleagues from related fields of science, for example, anthropology and zoology, the closest relative of a human is a chimpanzee. There are two types of chimpanzees: common and dwarf (bonobo). They separated relatively recently – 2 million years ago, and before that they separated from the branch that leads to man about 6-7 million years ago. Even earlier, the common ancestors of chimpanzees and humans separated from the ancestors of gorillas, orangutans, and even earlier – from the ancestors of other species of monkeys (slide 1). And today's lecture will be devoted to the questions of when, where, how and why the species Homo sapiens appeared.

I want to emphasize that I am presenting my private opinion, and not the ultimate truth, so some of the issues that I want to highlight are quite debatable, and I hope that we will have time to discuss them.

In order to understand how genetic changes led to the appearance of a person, how genes changed in evolution and these changes “made a person”, we will first consider a simpler question: how genes “make a person” in individual development, which we can directly observe, and the study of which does not require any complex reconstructions of the distant past.

So, how do you and I get out of the germ cell? To clarify this, I copied a slide from Mikhail Gelfand's lecture, which I really liked, and modified it a little (slide 2). In the last lecture, this was called an educational program, this is school knowledge, and I will remind them. Each gene has a structural part that encodes a protein, and a regulatory part that records when the gene should work and when not to work, i.e., under what conditions and during what periods of development of each cell this gene should be turned on and when off.

When a gene works, an RNA molecule is synthesized from it – an intermediary that transfers information to ribosomes – machines that synthesize proteins. Proteins, in turn, perform a lot of work in the cell, build it structurally, and perform various catalytic functions. Now it has become clear that RNA also performs many functions, only DNA has the function of an archive, and it seems that no functions have been invented for it anymore. A person has about 30,000 genes, and the set of genes in all cells of the body is the same. There are exceptions, for example, red blood cells in mammals, where the nucleus is absent, so that it is more convenient for them to carry oxygen, and there are simply no genes there. Or germ cells, in which the genetic material is mixed during maturation, and then it divides in half. But these are special cases. So, in all cells of the body, the set of genes is the same, but the cells are different: there are epithelial cells, there are hair follicles that produce hair, there is a gastric mucosa, etc. Hair in the stomach does not grow, and mucus is not released on the skin. Why? Because a certain set of genes works in each cell (slide 3). Many genes are silent, and different genes are silent in different cells. Figuratively speaking, we can say that each cell "sounds" its own chord of genes, and just as many different melodies can be played on the keyboard, so different chords begin to "sound" in the cells after fertilization of the zygote, creating different melodies and thereby leading the cells along different paths of development (slide 4).

The set of genes in different people is about the same (slide 5). Each of us has about 30,000 genes. But there are small differences: some genes in some people do not work, the work of others may differ markedly. Sometimes these differences do not manifest themselves in any way, but sometimes the difference is very significant. For example, if only one gene responsible for the growth of the body does not work, the disease achondroplasia occurs: bone growth disorder and a number of other disorders. The result is shown here (slide 6): this is Velasquez's painting “Meninas”, and the infanta's beloved dwarf has all the signs of this disease. This is the result of a change in the work of just one gene - the growth hormone receptor gene.

Those individual differences that distinguish us from each other are the result of mutations, old or recent. A mutation is a change in the DNA text. DNA consists of four "letters" – nucleotides, which record the genetic program of the body's development. Errors in the "rewriting" of these "letters" in the process of transmitting hereditary information from cell to cell, from generation to generation, are mutations. Some mutations persist for thousands of years, and some appeared only in our parents.

To explain how mutations change the structure of genes, I remembered an anecdote when a worker comes to get a job and is asked: “What can you do?” He answers: “I can dig.” “And what else?" - "I can still not dig.”

Using this analogy (slide 7), I will try to explain how mutations change the work of genes. So, the gene can work, let's take this as the initial level. A mutation can change the work of a gene or change the level of its activity, or it can lead to the shutdown of the gene. At the same time, the shutdown of the gene or a change in its activity level can be obtained due to mutations in the structural part that spoil the protein product, or due to mutations in the regulatory part of the gene, and then with a good structural part, the gene simply does not turn on and cannot say its word (slide 8). If the mutation has only slightly damaged the protein sequence or the regulatory part, in principle, we can expect that a reverse mutation will occur, and the gene will somehow repair and recover. But there are mutations when the gene is simply lost. And then the change is irreversible.

Like a conscientious worker, a gene can be very active, and this corresponds to mutations that increase the activity of either the protein encoded by the gene, and it starts working faster, or the activity of the regulatory site, and then many copies of RNA are synthesized compared to the initial situation and a lot of protein product.

We can hire a lot of workers to get the job done quickly, and there is a similar situation in DNA when multiple copies of a gene are created. Quite recently, a very interesting article was published, which stated that people differ from each other in the number of copies of the amylase gene. Amylase is an enzyme that breaks down starch. And it turned out that people who consume starchy food have on average 7 copies of the amylase gene, and those who do not eat so much starchy food have only 5 copies. The commentary to this scientific work was called “the photocopied gene". If you eat a lot of starchy food, it is advantageous when you have a lot of the enzyme amylase, so in such groups, people who had an advantage because of mutations, the number of copies of the gene increased.

There is also a special type of mutation that affects only the regulatory site, and these mutations change the time of the gene. A gene can work at different stages of development, for a long or very short period, and in the process of mutation, the time of the beginning or completion of some processes, for example, bone growth, changes.

And the last type of mutation: this worker decided to change his specialty and learn to play the violin. There are mutations that change the specialization of the protein, and they evade their original duties, change their "profession". A new function is usually a change in the structural part of a gene.

Now we know how genes work, how mutations change them, and we can now try to answer the question of how a monkey turned into a human. We give such a technical task to a geneticist – to turn a monkey into a human (slide 9). What needs to be done? The monkey has too much body hair, you need to turn off the gene that controls the formation of hair protein – keratin, and there will be fewer of them (slide 10 and slide 11). Compared to humans, monkeys have very long limbs. It is necessary to shorten the working time of the genes responsible for the growth of limbs, and they will become shorter (slide 12 and slide 13). Now it would be nice to add brains to the monkey (slide 14 and slide 15). Such genes that regulate the size of the brain – not one, but several – have been discovered recently. One of them is called the microcephalin gene, its changes have been found in patients with reduced brain size. Then it turned out that a person differs in this gene from a monkey.

What else can we add to our monkey? It would probably be good if she could learn to speak (slide 16). Genes that control the formation of brain structures necessary for speech learning exist. One of them was found during the study of a family where speech disorders were common. This trait was transmitted as a disease with a certain type of inheritance, sick members of this family could not master the rules of grammar, they could not learn to speak correctly, and they had a mild degree of mental retardation. The patients found a mutation in a gene called FOXP 2. Then it was shown that humans differ from monkeys by this gene. In a study on mice, it was found out that it works during embryonic development in a certain area of the brain, regulates the work of other genes, determining which of them is included in the work at this stage of embryonic development. Directs the work of genes that are involved in the formation of brain areas.

The genes that distinguish us from chimpanzees, which have changed during the evolution of the monkey, which eventually turned into a human, are revealed by comparing the DNA of a human and a chimpanzee. You've probably heard that there is a Human Genome project, and that human DNA has been completely read. Also, the DNA of chimpanzees has already been read, and, to a greater or lesser extent, the DNA of other primates. By comparing them, geneticists are trying to understand how we differ from other primates and find those genes that are responsible for the differences. They can be called "The genes that made us human." Those genes, the accumulation of mutations in which led to the appearance of a person. Mutations occur all the time, like grains of sand falling in an hourglass. It is assumed that the process of accumulation of mutations proceeds at approximately the same rate, although there are exceptions. But many mutations, having arisen, immediately disappear. And some remain and are passed on to the next generation.

According to the sequence of "letters" of DNA, a person differs from a chimpanzee by about one letter out of a hundred, while we differ from each other by one letter out of a thousand. This is a rough estimate. The difference of one letter out of a hundred is the changes that appeared both in the chimpanzee line and in the human line after their separation. Is it a lot or a little? Of course, it depends on where they are located and what to change, because some mutations do not manifest themselves in any way (they are "neutral"), and some are very significant. Now some genes are known, the changes of which led to the appearance of man. They are intensively studied. Therefore, after a while, geneticists will know which genes need to be changed to make a human out of a monkey. We have a man and a monkey, we can compare them and find out what these genes are. But how did this happen 5 million years ago, when the desired result was unknown?

Let's focus on one more detail: what are mutations and how do they occur? This is a change in the "letters"-nucleotides in the DNA sequence.

It is necessary to distinguish between the process of the appearance of a mutation in DNA and another process – that this mutation will not disappear immediately, but will persist at least for several generations or will spread and appear in people in the distant future. The process of mutation appearance is a chemical process. They occur quite randomly, it's just a chemical process that leads to a change in the molecule. And the spread of mutations in subsequent generations in humans (as well as in other organisms) is a population-genetic process.

The picture (slide 17) shows a number of people who differ in some way. In the next generation, the ratio will change, because someone will not have children, someone will have a lot of them. A generation later, a change will occur again, and, for some reason, some signs may disappear, and some become universal. The change in the frequency of signs can occur either randomly or purposefully, under the influence of selection. Selection is determined by environmental conditions, and different characteristics can be selected in different environmental conditions (slide 18). In some conditions, some options may be selected, for example, dark skin, and in others – light. Skin pigmentation is a genetically determined trait that probably had the greatest social and political consequences in the history of mankind. But there are also a number of other signs that have not attracted as much attention from society as skin color, but, nevertheless, groups of people of different origins may differ greatly in the frequency of a particular trait.

It is easy to illustrate how the environment dictates the conditions of selection on a certain basis. When studying athletes, it turned out that they differ in variants of the actinin muscle protein gene – a protein that is associated with oxygen metabolism in muscles. With a deficiency of this protein, aerobic metabolism increases, and when there is a lot of it, then anaerobic metabolism occurs. Let me remind you: if we get tired and our muscles ache, then this is the accumulation of lactic acid, which does not have time to oxidize with a lack of oxygen. Ie, muscles work so intensively that the blood does not have time to provide them with the proper amount of oxygen to oxidize the metabolic products that have appeared. And then, during rest, they are oxidized and excreted, and then our muscles stop hurting. It turned out that athletes who are engaged in strength and sprint sports, where there is a huge short-term load when the muscles work anaerobically, such athletes have genetic differences from ordinary people (slide 19). It turned out that compared with the general group that was used as a control, these athletes have less "aerobic" protein genes. Especially rare among them were variants when such "aerobic" variants of the actinin gene were obtained from both mom and dad. And among the Olympians, not a single one was found at all, so that both available gene variants (both the one received from mom and the one from dad) were "aerobic". Apparently, you can't become an Olympian in power sports if you got such a gene from one of your parents. Stayers who work on endurance have a higher frequency of the "aerobic" gene, and Olympic stayers have even more. That is, a certain task assigned to these athletes made a selection, and if this selection would have extended to the offspring, say, only sprinters would have multiplied, and stayers would not have multiplied, then we would have received a different ratio of frequencies of these variants in the offspring. The signs of offspring would have changed.

Another example of how the environment makes a selection. In Southeast Asia, a variant of the gene controlling the oxidation of ethyl alcohol is common, which gives a rapid accumulation of acetaldehyde after taking alcohol – a toxic product of alcohol oxidation, the one that causes a headache and other unpleasant symptoms. Almost half of the population of Southeast Asia does not have an enzyme that neutralizes this toxic substance. And most alcoholics have this enzyme active. The ratio of frequencies of different gene variants in the general population and in alcoholics is shown in the figure (slide 20). It can be seen that the ratio of alcoholics is changed. There are fewer people among them who have this enzyme inactive, simply because with an inactive enzyme, the accumulation of toxic acetaldehyde does not allow them to drink so much alcohol to become an alcoholic. But this is an example of selection that occurs according to momentary requests of the environment. And how did selection take place in human evolution?

To address this issue, I borrowed a fragment from a lecture by Kirill Eskov, and I will read it.

"Ramapitek is one of the variants of the "Asian project", which was parallel to the African ..." – this suggests that at the same time in different parts of the world there was a process of hominization, i.e., the transformation of a monkey into a human. In Asia, they also created a large upright primate, but on the basis of an orangutan, not a chimpanzee. There were, for example, wonderful giants – megantrop and gigantopithecus. And one of the options was ramapitek and sivapitek. And it may very well be that over time they would even evolve to something. But in any case, the "African project" managed earlier, and they solved the problems with everyone who interfered with them.

At this place, analogies are constantly being asked that "a tender is being held." Several design bureaus are given an order for a certain product. They put it up for a competition, then there are bench tests, etc. Then, in the end, some disappear, and a certain one model is adopted. Therefore, the idea of the "direction of evolution", on which many copies are broken, acquires flesh at this place, at first glance. In the evolutionist picture of the world, of course, no one gives tasks. Because the question "for what?" is categorically contraindicated to science."

End quote.

I will try to consider whether the customer was in the process of the appearance of a person, and if so, what exactly he ordered. Here in the diagram (slide 21) is a tree of species that, like our species, followed the path of hominization, but did not reach the final. On the right in the diagram is Homo erectus, a Homo erectus that came out of Africa and developed in Asia, and then became extinct. At this time, the hominid tree branched in Africa, and about 300 thousand years ago, one of the branches came out of Africa and successfully settled the Middle East and the southern part of Europe. It was a Neanderthal. We don't know how many branches remained in Africa. Among them were our immediate ancestors. About 60-70 thousand years ago, Homo sapiens emerged from Africa, which displaced all other species. For some time Homo sapiens and Neanderthal existed in parallel.

To find out if there have been any such directions of evolution, I want to start from the very beginning: since the appearance of life on earth. According to modern ideas (not genetic), the Earth originated more than 4 billion years ago. about 3.8 billion years ago, and life on Earth appeared. years ago (slide 22). This figure is not very accurate, but it does not matter to you and me, but what matters is that life has appeared. A cellular form of life appeared, in the form of so–called prokaryotic or nuclear-free organisms, from which nuclear organisms then appeared, which then successfully became multicellular, and among them mammals appeared, and among them primates, and our ancestors stood out from primates, and so until we appeared and came here to listen to a lecture.

At the same time, each new level of complexity arises on the basis of the previous one. The previous one does not disappear and cannot disappear. Each new species must be integrated with the ecosystem in which it arises, must be adapted to those processes, to those food sources that exist in this ecosystem. And food on our planet has been created before and is now being created by bacteria, fungi, plants. And if you destroy the bacteria, then the entire life support system on the planet will collapse. No one else can do their biosphere work for them. Animals consume plants, grind them at the same time, thereby helping the circulation of substances in nature, since it is much more difficult to oxidize non-crushed large plants and return their components to the biosphere, fungi and bacteria cannot cope. And predatory animals collect, so to speak, the cream from the biosphere – they receive concentrated resources that only need to be caught. Along the way, they keep these resources in good athletic shape so that they get caught by the teeth. This is in a very simplified form the current distribution of ecological functions between different organisms.

A similar distribution has always existed. Someone always ate someone, returning the organic matter that makes up the food to the circulation of substances. And he was food for someone else. There was quite an understandable competition – to eat yourself and not be eaten by others, while leaving offspring. Evolutionary inventions and tricks for solving this problem are very diverse. Today we are interested in one of the solutions that turned out to be relevant when other, simpler solutions did not work. This is gaining advantages through cooperation of efforts and division of responsibilities. For example, symbiosis. Organisms unite, everyone does something useful, and in certain conditions they have more chances to survive together than separately. By symbiosis, more complex nuclear (eukaryotes) organisms emerged from non-nuclear (prokaryotic) organisms.

But there is another way to increase the effectiveness of nutrition and protection – this is cooperation with their own kind. Transition from unicellular to multicellular. Then, on another level, the cooperation of multicellular with the formation of social systems, such as social insects (bees, termites) or social mammals. Here is the next step - combining simple social systems into more complex ones, and then complex ones into super–complex ones - only a person has done.  

I will give a very brief overview of further social evolution, because at the first lecture of Kirill Eskov there was a question in what the concepts of biological evolution are applicable to social. At the end of the lecture, references are given to the works of specialists on this topic. I believe that this should not be about the applicability of ideas about biological evolution to social, but about the fact that the evolution of both biological and social systems has common patterns inherent in the evolution of systems in general.

The simplest stage of human social evolution is the community. Communities can be egalitarian, where everyone is equal, or non-egalitarian, where someone has more resources and power, someone has less. The number of the community of wandering hunter-gatherers – cultural anthropologists call it a “LOCAL GROUP” - does not exceed two hundred people, and usually equals 20-50 people, extremely rarely in some very fertile areas can reach 500 people (if we are talking about sedentary higher hunter-gatherers or farmers). With the lifestyle of hunter-gatherers, the population density is about one person per 10 sq. km. (at least for those who had time to study in the XIX-XX centuries.) Hunting-gathering is a way of life that existed not only for hundreds of thousands of years of human evolution, but before that it existed for millions of years in monkeys.

If there are more than 200 people in the social system, then the organization should already be more complex. A more complex level is the unification of several communities, called CHIEFDOM. Unification occurs most often through conquest, while one of the communities becomes the main one, and the rest obey it. An alternative to such a system is an egalitarian system, when several communities unite into a single social organism, but the main community does not stand out. An even more complex society is when a system of chiefdoms is formed, either by conquering one chiefdom by another, or by dividing an overgrown chiefdom. The population of COMPLEX CHIEFDOMS ranges from 5 to 30 thousand . a person, usually at this level of complexity, society has already switched to agriculture or cattle breeding.

An alternative to a complex chiefdom is a TRIBE (this term has several meanings, one of them is used to refer to societies with a certain structure). Tribal associations can unite groups that have already passed through the stage of chiefdom, or they can form themselves by combining societies of other types. A SUPER–COMPLEX CHIEFDOM is an association of several complex chiefdoms. The polis organization, which has a complex history of origin, may be the result of the deirarchization of complex chiefdoms. Further complication leads to the emergence of states that are formed either from complex chiefdoms or from polis associations. States are not formed from tribes, because the tribe is not hierarchized.

Darwinian selection of the most successful combinations of inherited random variations of traits (here traits are certain characteristics of communities, chiefdoms, etc.) is also applicable to social evolution, but the nature of the variation of traits, the traits themselves and the way they are inherited there, of course, is different.

In the scheme discussed above, there is a small addition to the theory of evolution as it is presented in many textbooks: the allocation of certain levels of complexity of systems.

That is, we have now considered not any changes and directions of evolution, but those in which elements were combined into a more complex system. Into a system of a different level of complexity.

The simplest is nuclear–free prokaryotes, then more complex unicellular nuclear organisms appeared (as a system of closely interacting prokaryotes), then multicellular organisms (as a system of interacting cells), then social organisms (systems of interacting multicellular), within which human society emerged, and then there were stages of social evolution characteristic only of humans.

Such levels in evolutionary development (slide 23) were called metasystems by Valentin Fedorovich Turchin, and the complication with the transition to the next level was called a metasystem transition. From my point of view, this is a very important addition to Darwin's theory in all its modern guises.

If a complication is required, i.e., a transition to some other level of complexity, then this transition can appear simultaneously in different places and the one who transformed first gets an advantage over the others and can beat them in the competition (as shown on slide 23 in the right part). Just the tender that Kirill Eskov was talking about.

I am telling all this in order to emphasize that every species that appears on Earth must be adapted to the conditions in which it appeared. For example, when eukaryotes arose, they did not arise in an airless space, but on the Earth inhabited by prokaryotes. Then multicellular ones arose, which had to adapt to life among unicellular ones. The emergence of social organisms occurred in a very complex environment, including beings and systems of all previous levels.

And finally, when man appeared, it happened in conditions when there were groups of other primates for millions of years. And here you can search for the request that the environment presented to these primates (slide 24). The fact that the wool has disappeared, of course, is not the main thing, and walking upright, although very useful, is also not the most important principle. And what was important?

A remark from the audience. Mind.

Borinskaya. And what advantages does it give? What functions does thinking perform?

A remark from the audience. Experience.

Borinskaya. I.e., the transfer of experience from generation to generation. Monkeys already have it, and humans could also do it more efficiently. In the transfer of experience, the appearance of mammals was fundamental. They have two generations in mandatory contact, as the mother feeds the cub. This creates the basis for the non-genetic transmission of information from generation to generation, i.e. for the emergence of culture. This method appeared much earlier than man appeared. Until recently, it was believed that animals could not have a culture, and now there are discussions about how to call the training from adults that baby monkeys have: call it a protoculture or culture, and where is the boundary that distinguishes a person from a monkey by this criterion.

So, thinking allows us to transfer experience from generation to generation, to accumulate it. Is there anything else that thinking would be useful for?

A remark from the audience. Communication.

Borinskaya. And why is it needed?

A remark from the audience. To organize with other people, to do some kind of common cause.

Borinskaya. For example, to successfully get food or defend yourself from someone. We have become smarter than the neighboring herd, we reach the banana tree faster and pick bananas better. It is possible not to complicate further. And yet further development was taking place. What are your ideas? Why man has been getting smarter, more capable of communication and more organized over millions of years.

A remark from the audience. There was a speech, a language.

Borinskaya. So what if there was a speech? Further complication is not necessary. Sit there and eat bananas, all the monkeys have already been driven away.

A remark from the audience. Competition.

Borinskaya. A wonderful idea: but the competition is not between individuals within the group, but the competition of the group itself with other groups close to the evolving level of development, had to move a person to wiser all the time. There are other theories like that it was necessary to crack a bone or pick something out with tools from somewhere, but such requests are instantaneous, they cannot act all the time. I.e., assuming that the request of the environment for wiser, strengthening the development of means of communication, was the presence of other groups with similar skills, and the winner was the one who cooperated better, was better organized in defense and attack, then it can be explained why a person had to steadily get smarter, develop speech and communication skills. And as we have seen with athletes or alcoholics, if there is a request, then genes provide it.

I can give an interesting example of how quickly communication and social interactions can be developed. Some indirect answer to this question is given by experiments conducted in Novosibirsk on breeding silver foxes. They were bred on farms. These animals have very good fur, but the animals themselves are very aggressive, it was difficult to keep them, so the selection for the domestication of silver foxes was started. It was necessary to get less aggressive animals. It succeeded: those animals that were less afraid of humans were selected for brood. They were selected as follows: a person approached the animals, and noted which foxes were less afraid of him, took less aggressive poses, did not show their teeth, etc. They were taken for brood. For twenty generations of such selection, it was possible to obtain animals completely domesticated (slide 25). Foxes appeared, who, like dogs, fawned over the man, treated him very warmly and were very happy about his appearance. But besides that, there have been some other changes in them. Their tail began to curl in a ring, also like a dog's, their ears drooped and they began to yap. And their fur has also become bad. Although no selection was carried out on these grounds.

Eyes. And how was wool related to aggressiveness or environmental change?

Borinskaya. It turned out that these are conjugate changes. Not all genes have been identified in these foxes yet, but some genes that have changed as a result of such selection are already known. These are genes that control the work of hormones and regulate the transmission of nerve impulses. The fact is that some substances that work in the nervous system during the transmission of an impulse are involved in general metabolism, including in the production of pigments. There are common links in the synthesis pathways of substances involved in the formation of pigments and in the transmission of signals. Due to the fact that there was a selection on one basis, another was hooked.

Eyes. Is it just an accident or does it depend functionally on the behavior?

Borinskaya. This is a feature of the structure of metabolism. I can give an example when anthropologists tried to find out whether patients with schizophrenia differ from healthy ones, made a bunch of measurements and eventually revealed one sign: the patients had darker hair. This does not mean that all brunettes are schizophrenics. The fact is that in schizophrenia, the metabolism of a substance called dopamine changes, and the dark pigment is formed from the same precursor as dopamine. Therefore, when dopamine synthesis changes, some links of pigment synthesis are also captured.

Eyes. That is, in this case, with foxes, is it an accident? They could theoretically become more beautiful.

Borinskaya. We'll leave it for later, and I'll tell you why everything on Earth evolves at all.

Would the bacteria live, not change, what is wrong with them? Why didn't everything stop at some level of development? Apparently there is a continuous environment query. Here in the picture that I took from the article by Georgy Alexandrovich Zavarzin, an interesting aspect of the structure of nature is the circulation of substances (slide 26). Biogeochemical machine of the planet. And it, this machine, is controlled by living organisms, i.e., on each cycle and on any available process, there are some types of bacteria that control this process. More organized creatures sit on them and eat them and control their numbers, etc. This system creates requests for the emergence of new species and for the creation of new ecological niches. I assume that this system was the customer of human evolution. And this evolution took place in the conditions that then existed. And at that time there were groups of animals, highly developed primates.

And here there is another important point, non–genetic - how man and his civilization interact with the biosphere. There are two models of interaction: one is that civilization is a kind of octopus that sits on the biosphere, eats it up, and soon everything will collapse. And the other is that civilization is inscribed in the biosphere, that there are some mechanisms for regulating the appetites of mankind, and the existence of such mechanisms. This idea is illustrated by pictures (slide 27), which I took from the presentation of geographer Dmitry Lurie. The mechanisms that regulate the activities of mankind are very interesting. As resources are exhausted, a person has to change the ways of extracting resources, and, accordingly, the environment of his existence. And here we can go back to the genes again.

The way a person himself changes his environment as civilization develops is reflected in his genes. Two short illustrations of what happened to a person after he appeared. Let me remind you once again that he appeared as a hunter-gatherer, these are groups roaming a certain territory, catching animals there and collecting edible plants. Earlier, 15 thousand years ago, all people were hunter-gatherers. 500 years ago, only one percent of hunter-gatherers remained, and by the end of the XX century there were very few such groups, and all other people switched to a civilized way of life: agriculture, cattle breeding and other occupations. At the same time, the environment can be divided into components: natural (climatic conditions, landscape), biogenic (availability of food, presence of infections) and anthropogenic – this is the part of the environment that man created himself.

Let's look at examples of genetic changes caused by these different factors.

Adaptation to climatic factors. Back in the XIX century. it was noticed that if there are groups that differ in size, then smaller species tend to a warmer climate, and larger ones – to a cold one, because if the bodies are large, then the heat loss is less. This is also true for humans. Anthropologists have long determined that the average weight of people in different climatic and temperature zones is different (slide 28). Another pattern found for – the protruding parts of the body are longer where it is warm, shorter where it is cold (slide 29). The same examples of differences in body structure can be found in humans (slide 30). These differences are inherited, that is, determined genetically.

Resistance to infections. It is known that in areas where malaria is found, there are also protective mutations of the body to them. Interestingly, these mutations were discovered during the Korean War, when American soldiers were given the drug primachine, which was supposed to protect them from malaria. But some soldiers died not from malaria, but from this medicine itself. When an investigation was conducted, it turned out that these soldiers carried a mutation in one of the genes, and they were from the Mediterranean or from Africa, i.e., from areas where malaria is common. So one mutation was discovered, then it turned out that there were several of them. They arose independently, but provided a solution to the same problem – malaria resistance (slide 31).

A similar example is not related to the environment, but to the appearance of new food. During the domestication of animals, humans gained access to milk. In all mammals, the baby can digest milk during feeding, and at the end of this period, the enzyme that breaks down milk sugars disappears. But in some people, the synthesis of this enzyme continues until adulthood. And if this enzyme is not present, then you can drink milk, but then it will be very bad: the stomach will hurt, etc. It turned out that 100% of Finns babies assimilate milk, and only 85% of adults have this enzyme and can drink milk, and 15% of adults do not have the enzyme and milk is bad for them. And in Japanese, only 2% of the adult population can drink milk without consequences (slide 32). The mutation occurred in the regulatory region of the gene that encodes an enzyme that breaks down milk sugar, and there are several mutations: one of them is common in Europe, the second in the Middle East, the third in Africa (slide 33). In Asia, such mutations have not yet been discovered, and the population there, for the most part, does not drink milk. The mutation selection process was the same: an order was given from Wednesday, and the genes implemented it.

And the last illustration of how selection can work. Here (slide 34) presents data on the population change in China over the past two thousand years. The Chinese emperors conducted a population census, not so that it would be convenient for us to investigate it, but for the purpose of taxation. When these data were collected together, it turned out that every 150-300 years there were sharp declines in numbers, here, for example, from 60 million to less than 20. Such crises have occurred not only in China, but also in other regions. After the introduction of modern medicine, they have become less harsh. There are several factors at work during crises: war, famine and epidemics. If it is famine or epidemics, then it is clear that crises will act as a powerful factor in selecting those gene variants that will protect people from the epidemic or make them more resistant to food shortages. Periodic fluctuations in numbers accelerate the effect of selection and are accompanied by changes in genetic characteristics important for survival.

I want to thank those with whom discussions helped me to prepare this report - Nikolai Yankovsky, Vladimir Spiridonov and Vladimir Alyoshin. Thank you all for your attention.

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