What was Darwin right and wrong about? What is evolution and according to what laws does it function? For what reason are the females so picky and how does the living differ from the inanimate? Why, thanks to the development of medicine, the average life expectancy will be reduced to 30 years, and infant mortality will increase to 60%, and what to do about it? The famous biologist Alexander Markov told us about this.
Alexander Vladimirovich Markov - Doctor of Biological Sciences, paleontologist, leading researcher at the Paleontological Institute dnhjt RAS, head of the Department of Biological Evolution at the Biological Faculty of Moscow State University. Winner of the main prize in Russia in the field of popular science literature "Enlightener", laureate of the award "For loyalty to science" of the Ministry of Education and Science of the Russian Federation in the category "Popularizer of the Year".
Contributed to the development of the general theory of biological macroevolution and mathematical modeling of macroevolutionary processes. Author of over 180 scientific publications and many popular science, including well-known books: "Human Evolution: Monkeys, Bones and Genes", "Human Evolution: Monkeys, Neutrons and the Soul", "The Birth of Complexity", "Evolution. Classic Ideas in the Light of New Discoveries”(co-authored with Elena Naimark). One of the authors of the site Elements.ru, founder of the portal "Problems of Evolution".
Alexander Vladimirovich, everyone has heard about evolution, everyone supposedly knows what it is. But if you go out and ask this question, hardly anyone will say anything intelligible about this. So what is evolution?
- This question is too comprehensive. The fact is that the fact of evolution underlies literally all modern biological research, theories, directions, etc. This is not some kind of separate branch that exists by itself. It exists in close connection with all facets of modern biology. Therefore, the normal course of the theory of evolution, or, better to say, evolutionary biology, is designed for 30-60 lectures. Unfortunately, people prefer primitive information that allows them to create the illusion that they know and understand something. This even somewhat devalues the achievements of science. But those who are really interested in this topic and who want to understand it will not be limited to short information. And the rest, well, let's try to help create this illusion. In a nutshell, the theory of evolution is a huge body of knowledge about how the evolution of the organic world occurs. The fact of evolution is an absolutely firmly established truth and does not need any additional proof for a long time.
By what laws does evolution function?
- Probably the easiest way to answer this question is to give a brief historical overview. Modern evolutionary biology nevertheless began with Darwin, with his work "The Origin of Species", which even today is very interesting to read - it, as was customary then, is written in a living, understandable language. This is a rather rare case in the history of science, when a scientist who lived in the middle of the 19th century (at that time, very many of the most important facts in this matter were simply not known; for example, no one knew what heredity is and how it works, what is the nature of variability why children are like their parents), we managed to correctly guess the main most important principle underlying the evolution of all living organisms - the principle of natural selection, on which everything is based to this day. Although, of course, a huge amount of new knowledge has been added to the fundamental ideas of Darwin today.
By the way, what was Darwin wrong, and what was right?
- This question, perhaps, is not even so interesting, because 157 years have passed since he wrote his book. He knew neither genetics, nor molecular biology, practically nothing of what modern biology knows, so it is not very correct to understand what he was wrong about, of course. He was wrong in those arguments that were based on the vague notions of the nature of, say, heredity, accepted at that time in science. At that time, no one knew about genes, chromosomes, Mendel's laws, that heredity is discrete.
Therefore, Darwin proceeded from the assumption of a fused heredity - the views that existed at that time. And for him it was a very, very difficult question about why organisms remain variable. After all, if the hereditary rudiments of the parents in the offspring merge into a single indistinguishable mass, all this should lead to the fact that all individuals in the population will very quickly become exactly the same. That is, if heredity is continuous, and not discrete, variability should disappear very quickly. It was incomprehensible. Therefore, to say that the idea of merged heredity was Darwin's mistake would be dishonest to him.
Another example. At the time of Darwin, there was a generally accepted point of view that acquired characteristics, such as the results of exercise and non-exercise of organs, all kinds of muscles trained or, conversely, atrophied from inaction, can also be inherited. Special experiments have not yet been carried out that refuted these ideas. Accordingly, Darwin used this to explain many of the facts. But the point is not where Darwin was wrong, but where he was right. Take any naturalist of those years, and from the height of modern knowledge, we will find in him a huge number of "mistakes". The most amazing thing is that Darwin, without even knowing what heredity and variability are, correctly guessed the main principle of natural selection. And modern ideas are still based on it. That is, it has indeed been proven that natural selection works, that it is the most powerful of forces. And in recent decades, when we entered a new era of genetics and were able to compare genetic texts, hereditary material of different species, it turned out that from these texts you can directly see exactly where natural selection worked, what was its type, which genes it acted on. with what force, etc.
What was the further development of biology?
- The first stage is the beginning of the 20th century, when Mendel's laws were rediscovered (principles of transmission of hereditary traits from parental organisms to their descendants - NS) and classical genetics with its chromosomal inheritance appeared. At first, it seemed to many that genetics contradicted Darwin's views, because he wrote about very small, barely noticeable changes, and genetics initially worked with very strong mutations - all kinds of deformities. They are easier to spot and study. But by the 1930s, it became clear that there was no contradiction here, that there was a huge number of mutations with small effects, that almost all traits were polygenic, that is, they depend on many genes that make a very small contribution to them. And, accordingly, this makes Darwinian evolution not only possible, but also inevitable. When we learned that heredity is not fused, but there are discrete units - genes, we figured out their effects, it became clear that natural selection must necessarily work and lead to an increase in fitness over time. This is what Darwin predicted. Formed the so-called synthetic theory of evolution (synthesis of genetics and the teachings of Darwin. - NS). It is mistakenly considered by some to be the state of the art of evolutionary theory. No, and this theory, too, will soon be one hundred years old. Since then, there has been further powerful development: new research has been carried out, new facts have emerged.
What happened next?
- The next revolution takes place in the 1950s – 1960s, when the structure of DNA was discovered and finally the material nature of heredity was discovered, the genetic code was deciphered, general principles of how hereditary information is recorded in DNA, how it is read and embodied in a particular organism. It was the greatest breakthrough - people began to understand how evolution occurs at the deepest, most basic level. And finally, the current genomic revolution, which already allows us to directly read genetic texts and compare the genomes of different individuals, different species.
We can calculate that in the past, say, a hundred thousand years, natural selection in human populations has acted on a particular gene. That is, it supported some kind of mutations in specific genes, because they were useful, increased reproductive success. And in other genes, for example, all mutations turned out to be harmful and were discarded. Such things are very clearly visible and one can compare evolution in different lines and conditions. And many very important additions were made to the general outline. As, for example, the theory of neutral evolution. After all, Darwin considered primarily beneficial random changes and only partially harmful ones, those that should be rejected by selection. But already in the middle of the last century, it became clear that a huge role in evolution is played by neutral mutations, which are neither useful nor harmful, but still change something.
They arise and accumulate in populations and later, as it turned out, can play an important role in evolution. Not all differences between species have some kind of adaptive meaning. Many are simply the result of the free accumulation of neutral mutations. But this randomness is subject to very strict statistical laws. And, in particular, thanks to these patterns, we can calculate the lifetime of the last common ancestors. The accumulation of neutral mutations is ongoing. Of course, the speed of this process is not entirely constant, there are a number of complicating factors, but in the first approximation it can be called the same. The principle of the molecular clock is based on this. With its help, comparing neutral changes in the genomes of two species, one can say when their last common ancestor lived approximately.
Tell us about the basic laws of evolution
- The basic law is a combination of heredity, variability and differential reproduction. Why is evolution happening? Objects that are capable of Darwinian evolution are called replicators. A replicator is an object that has four properties. The first is the ability to reproduce. That is, the replicator must by any means contribute to the production of its own copies - other objects similar to itself. The second property is variability. This means that the copies do not have to be 100% exactly the same as the parent object. At least sometimes there should be some random changes. The third is heredity. This means that at least some of these randomly occurring deviations must be hereditary, that is, be inherited by the next generation.
Moreover, in order for the replicator to evolve effectively, the quantitative indicators of changes must be within certain limits. That is, the variability should not be too great, but should ensure the stable reproduction of some basic properties of replicators in the course of generations. If there are too many mutations, then hereditary information will be lost. And, finally, the fourth property is the dependence of the reproductive efficiency on the hereditary characteristics of the organism. This means that at least some of the hereditary deviations should affect - positively or negatively - the efficiency of reproduction, that is, how many copies of itself a given object will create and pass on to the next generation.And, by the way, the efficiency of reproduction does not mean the speed of such, not just fertility - a million eggs laid out and that's it.
You need to understand that this means the number of offspring that you have produced and who have successfully survived to their own reproduction. The efficiency of reproduction will be more correctly assessed not in the number of children, but in the number of grandchildren. Although this is also not an ideal estimate. So, if all four conditions are met, such an object cannot but evolve according to Darwin, it is simply doomed to do so. And the final proof of this was the decoding of the structure of DNA. The replicator and its four properties are the basic principle underlying evolution. And the dependence of reproduction on hereditary characteristics is natural selection. In simple terms, this means that individuals with some hereditary traits reproduce more efficiently than individuals with other traits. And, accordingly, the population becomes more of those traits that provide more efficient reproduction.
What is sexual selection?
- Sexual selection is a very interesting, specific form of natural selection, characteristic of those organisms that have a division into males and females. Sexual selection is a very striking mechanism that leads to very impressive results. Often, traits that evolved to look attractive in the eyes of a butterfly, for example, look attractive in our eyes too.
Combinations of bright colors attract not only butterflies, but also people - due to some fundamental principles of the nervous system of all animals. But let's go directly to sexual selection. In many cases, the male's main job is to get the female's attention. Indeed, in order to reproduce effectively, one must not only survive, escape from predators and eat well, but also find a sexual partner. And preferably high-quality, with good genes. Otherwise, you will have weak offspring.
If you have the opportunity to leave offspring from many partners, then it is beneficial, accordingly, to find many partners. But this in most cases only works for males. Because males produce small and cheap sex cells, but in huge numbers. Whereas females produce large eggs, of which there are a limited number. In different species, everything, of course, is very different, but the basic situation is such that male opportunities for reproduction are in abundance, and female ones are in short supply. Therefore, it is beneficial for a male to mate with a large number of females: the more females he fertilizes, the more children he will have. And the female, on the contrary, is not profitable - one male is enough for her, which will fertilize all her eggs. From the fact that she mates with a thousand males, she will not have more children.
Therefore, males often begin to compete with each other for female attention, and they develop various adaptations that help to win this competitive struggle. For example, the weapon is the antlers of deer or stag beetles. Or all kinds of bright decorations - spots on the wings or tails. And females, on the contrary, develop fastidiousness. After all, if they are actively competing for her, she needs to be picky so as not to be mistaken in choosing the best partner. Therefore, in order to master such a female, the male has to make absolutely incredible efforts. This is especially evident in birds of paradise or such wonderful birds as bowerbirds, who build real palaces from twigs, and in every possible way they are decorated with flowers, berries, shells. They select objects for their huts by color, by size. For one of the views, the use of optical illusions is even shown, which are sometimes used in architecture to make the building seem larger than it is.These birds arrange pebbles on the platform in such a way that the female, which stands in the middle of the gazebo, seemed, looking at the male, that he is larger than he really is.
Here you really think that intelligence is the result of not only adaptation to external environmental conditions, but also sexual selection …
- Yes, there is such a well-respected hypothesis that the leap in the development of the human brain is associated, among other things, or even, perhaps, primarily with sexual selection. Because highly developed intelligence is a good indicator of fitness. And females, perhaps, benefit from the signs of the male's intelligence when she makes a choice. Since a perfectly functioning brain is a good window into the genome. Indeed, for the good development of the brain, the coordinated work of hundreds and even thousands of genes is needed.
If some of them are spoiled, then it is likely to affect intelligence. Demonstrating his wit, eloquence and creativity, the male thereby shows the female that he has very good genes and the offspring from him will be healthy. Sexual selection can also generate positive feedbacks. A trait can swell to incredible proportions, because the very fact that parts of the females like the trait makes it beneficial to the male. Accordingly, selection maintains this trait in the male.
But choosing this trait becomes beneficial for other females, because their sons will inherit it, which means, in turn, more females will like it. Therefore, the very fashion of the trait makes it useful. It turns out a chain reaction and the sign can grow to gigantic proportions. And in human evolution, the brain volume quickly - in 2 million years - increased by as much as three times. Therefore, it is possible that sexual selection took part in this.
How does the living differ from the inanimate, the properties of replicators?
- You're right. Many philosophers have tried to answer this question, but the difficulty is that we know only one form of life, which, as we now know, has a single origin, a single genetic code. Therefore, we do not know what features of our earthly life are obligatory for life in general. And since NASA is looking for life on other planets, and they need to understand what, in fact, they should be looking for - these guys seriously asked the question of the difference between living and non-living. And they came to the conclusion that any chemical system capable of Darwinian evolution should be considered alive. That is, any chemical replicator. This definition does not fit computer viruses, which could also be considered alive, especially if they were given the opportunity to mutate freely. But there is a catch - they are not of chemical origin.
The development of medicine has led to the fact that natural selection has decreased. From the point of view of ethics, this is great, but from the point of view of biology?
- Natural selection is a wonderful creative force that has created all the diversity around us. But from a human point of view, natural selection is extremely unpleasant. And none of us wants to be exposed to it. As it used to be, in the Middle Ages, when infant mortality was 60%, and the average life expectancy was 30 years.
It can be assumed that then the healthiest, strongest, strongest, most capable, etc. survived. Natural selection acted and rejected any harmful mutations. But thanks to the development of civilization, its effect weakens. People with such inherited mutations survive, which would have died earlier. On the one hand, this is bad for our gene pool - these mutations weaken the health of mankind, reduce its intelligence, accumulate more freely in the gene pool.
And if nothing is opposed to this, they will continue to accumulate freely, people will be less healthy and more stupid. Indeed, in modern civilization, a person, even with very low intelligence, still reproduces well and leaves offspring.In some societies at some stages of history, even in our societies, an inverse relationship also arises - people with low intelligence reproduce better than people with high intelligence. This is direct selection for stupidity. Which, of course, is not good at all. Because a society in which stupid people are numerically predominant is a degraded society in which violence and cruelty, ugly social institutions will flourish. Because genetic degradation is necessarily associated with social degradation.
What can be opposed to this?
- It is not entirely clear, but, in principle, there are only two ways in the future. Or we do nothing and the situation continues to grow - our health is weakening and we are increasingly dependent on doctors. But due to the accumulation of harmful mutations, even the most highly developed medicine will quickly cease to cope with the increased workload.
And even, despite the presence of colossally advanced medicine, everyone will work all their lives only for medicines, and still everyone will be sick and stunted, and they will still die at the age of 30, and still there will be infant mortality, as in the Middle Ages. We're back to where natural selection is working again. This is a pessimistic scenario. The optimistic one is that science will have time to come up with effective methods of consciously correcting our genomes in order to take evolution into its own hands, so that high biotechnologies work instead of natural selection and correct harmful mutations in the genes of embryos.
And in the future, they even picked up some kind of design, improved the hereditary qualities of future children. Of course, there will be a lot of all kinds of ethical, social and legal problems, but the fact is that we have no other way. Either a return to the medieval nightmare, or the path of development of biotechnology. There is no third. I really hope that humanity will choose the second path.