Conclusion from Alexander Markov's "Human Evolution"

A. Markov. Human Evolution. In 2 books. - Moscow: Astrel: CORPUS, 2011. Presented here is a fragment of Book 2 (pp. 471-499). Part of this material has already been published online; the conclusion of the book is reproduced here in full with the agreement of Alexander Vladimirovich Markov. The purpose is use in the educational process (and, where possible, popularization of this wonderful book).
A. Markov. Human Evolution
Conclusion
Evolution continues

Many people are curious whether human evolution is continuing today, and if so, where it is heading. Will we become smarter than we are now? Will we have a "massive" head on a tiny body and fingers adapted to the QWERTY layout? Or no, only the left hand adapted to QWERTY. The right one - to the mouse. Or perhaps we will simply die out under the weight of harmful mutations?

As a rule, serious scientists refrain from such forecasts, citing a lack of data, underdeveloped models, and the high degree of stochasticity of the processes under consideration (that is, the great role of chance in evolution in general and in human evolution in particular). All of this is true. But I have already hinted several times at my attitude toward excessive seriousness. All the more so because some well-grounded statements can still be made.

Let us start with the fact that the biological evolution of humans has not stopped and is unlikely ever to stop. This can be demonstrated, so to speak, "on one's fingers", which is exactly what we shall now do.

Evolution is, first and foremost, a change in the frequencies of alleles (genetic variants) in a population. The two main mechanisms for changing allele frequencies are genetic drift and natural selection. Let us start with drift.

Genetic drift is random, undirected fluctuation in allele frequencies. Under the "jurisdiction" of drift fall, first and foremost, neutral genetic differences, that is, those that do not affect, or only weakly affect, an individual's reproductive success (the number of offspring left behind). Random fluctuations in allele frequencies are absolutely inevitable, if only because, owing to a huge number of diverse random causes, different individuals leave different numbers of offspring. We looked at an example of genetic drift at work in the chapter "From Erectus to Sapiens", when we talked about mitochondrial Eves. The inevitability of the appearance of these Eves is one of the consequences of genetic drift. This example shows that, for all its randomness, genetic drift leads to quite predictable consequences.

Because of drift, allele frequencies are constantly, gradually changing. And this means evolution is proceeding. Only a miracle could stop drift. For that, an allele whose frequency in a given generation is, say, 25.0632001%, would need to have exactly the same frequency in the next generation. To the precision of every digit that corresponds to a whole number of people. And its frequency would have to remain exactly the same in the third generation. And in the fourth, and the fifth, and always.

How could this be achieved? Well, one could force every person to have exactly two children - no more and no fewer. One boy and one girl. That would help, but not much. Because each child receives a randomly chosen half of your genes. Some genes are bound to be luckier, others less so. Some of your genes will go to both children, some to neither. To fully stop drift, one would have to take control of the formation of germ cells - gametes - as well. One would have to specially take from every person two such gametes with no repeats whatsoever, in which absolutely all of that parent's genes are represented, each in exactly one copy. A simple selection from the existing variety of gametes will not do here, especially in women. They produce far too few egg cells. One would have to artificially engineer the genomes of the gametes. A hellish labor - and one utterly useless to anyone.

Because of drift, as we saw with the example of mitochondrial Eves, any neutral allele will sooner or later inevitably reach either zero or one-hundred-percent frequency. That is, it will either become fixed in the population or disappear. The probability of the first outcome (fixation of the allele in the population) equals the frequency of the allele at the given moment in time. If the population is large, fixation may take a long time to wait for - thousands, tens of thousands of generations. In a small population, neutral alleles disappear and become fixed faster.

But in a small population, fewer new mutations arise as well. For example, each newborn human, according to existing estimates, carries about 100 new mutations that were not present in their parents. Most of these mutations are neutral, some (perhaps around a dozen) are harmful, and beneficial mutations appear extraordinarily rarely. For the sake of simplicity, let us for now assume that all mutations are neutral. Then, in a population of a thousand people, 100,000 new neutral mutations arise in each generation. In a population of a million people - 100 million mutations. Some of these will eventually disappear from the gene pool, some will become fixed, that is, reach one-hundred-percent frequency.

The probability that a new, just-arisen neutral mutation will end up becoming fixed in the population, rather than disappearing, is inversely proportional to the size of the population. The number of mutations arising in a population is directly proportional to its size. In the end, if we wanted to calculate the rate at which new mutations become fixed in a population, the population size in our equation simply cancels out. The rate of fixation of mutations does not depend on population size! It depends only on the rate of mutagenesis (in our case - 100 mutations per individual per generation). Moreover, I'll let you in on a secret - it is simply equal to that rate. If our mutagenesis rate is 100 mutations per individual per generation, it follows that in each generation approximately 100 neutral mutations in humanity's gene pool reach one-hundred-percent frequency.

As a result of drift, the population is invariably changing, accumulating neutral mutations. Here, "neutral" does not mean "not manifested in the phenotype". They can be manifested; they simply do not noticeably affect reproductive success. As an example of such a trait, determined by a single gene and evidently not affecting reproductive success, one can cite the ability to roll one's tongue into a tube. Perhaps, after thousands of generations, this ability will be possessed by everyone on Earth. Or, conversely, by no one. This too is evolution.

However, on drift alone one won't get far. Drift cannot ensure sustained evolutionary movement in some particular direction. It cannot lend evolution directionality, since it mostly governs neutral genetic differences. It is incapable of creating a new adaptation.

Natural selection can do all of that. Does selection act on present-day humans? For some reason, many people think not. It's hard to say where this myth arose. In fact, stopping selection is no easier than putting an end to genetic drift. Judge for yourself: for selection to stop acting on humans, it would be necessary to reach a point where no genetically determined differences between people whatsoever affect the number of offspring left behind. For that, for example, the most severe hereditary diseases would need to affect reproductive success no more strongly than the ability to roll one's tongue into a tube. It is obvious that, on average, people burdened with a large number of harmful mutations leave fewer offspring than people who have few harmful mutations (by "harmfulness" we will, for now, mean harm to health).

The matter is not limited to hereditary diseases alone. Recall the first law of behavioral genetics: all behavioral traits depend on genes! Can one, while remaining of sound mind, assume that the number of children a person produces does not depend on their behavior?

There is no doubt that selection continues to act on us. But exactly how - that is a complicated question, and specific facts are still few. It is obvious that the direction of selection in post-Paleolithic societies depends radically on culture, on the way of life accepted in a given society. The Japanese, perhaps, were selected for the ability to digest seaweed, pastoral tribes - for lactase persistence in adulthood, many African peoples - for resistance to malaria, nomadic hunter-gatherers of South America - for adventurousness and a drive toward novelty. But for tribes that do not consume milk, lactase persistence in adulthood is a useless and even a slightly harmful trait (resources are wasted synthesizing an unnecessary protein). For settled farmers, the "adventurousness gene" is slightly harmful. And so on. The direction of selection differs across different cultures.

Meanwhile, cultural evolution in recent centuries, in most societies, proceeds at such a rapid pace that the factors of selection probably manage to change direction several times within the lifetime of a single generation. Until people's way of life "settles down", until the social environment stabilizes - in general, until humanity's social and cultural development comes to a halt (and, honestly, I hope this does not happen in the coming millennia) - it is rather pointless to speak of reliable and detailed evolutionary forecasts. Let historians and sociologists lay out for biologists, in all its details, the sociocultural development of humanity for the next 100,000 years, and then biologists may perhaps be able to give a well-grounded forecast of the further course of the biological evolution of *Homo sapiens*.

In general, if the reader is disappointed by the absence of clear forecasts in this book, let them know: historians and sociologists are the ones to blame.

As for concrete facts about the direction of selection in our day, they are not yet very impressive: too few such studies have been carried out, and too few traits that could potentially affect reproductive success have come under researchers' scrutiny.

For example, there is data on the relationship between the number of children and such personality traits as extraversion and neuroticism. Both of these psychological characteristics are heritable to a significant degree (Viken et al., 1994). Extraversion in men, as a rule, correlates positively with the number of sexual partners and with social status. For some present-day societies it has been shown that extraverted men leave more children compared to their introverted compatriots. However, extraverts on average more often end up in dangerous situations and get injured. Perhaps this offsets their advantage (and that's why introverts haven't died out yet). A high level of neuroticism in women may increase fertility, but at the same time reduce the "quality" of offspring (the children receive less care, which reduces their chances of successful reproduction). A low level of neuroticism, conversely, is associated with fewer children, each of whom receives more investment of resources. Maximum reproductive success may in the end belong to women with an intermediate level of neuroticism. Unfortunately, such studies have so far only been carried out on individual cultures, and it is not clear how universal such patterns might be (Alvergne et al., 2010).

One more example: based on the results of 6 years of observation of 5,000 women living in North America, it was shown that selection today favors the following female phenotypic traits (Coyne, 2009):
1. height slightly below average (a decrease in the average height of North American women of 2.1 cm over the next ten generations can be expected);
2. weight slightly above average (women gain 1.4% over ten generations, if the pattern of selection does not change);
3. low blood pressure and cholesterol levels (cholesterol will drop by 3.6%, blood pressure by 1.9% over ten generations);
4. earlier first childbirth (the average age at which a North American woman gives birth to her first child will decrease over ten generations by 1.7%: from 26.18 to 25.74 years);
5. later onset of menopause (will increase by 1.6%, or 0.8 years, over ten generations).

Nevertheless, even these (frankly, not very exciting) conclusions are not final and are not without dispute. The calculations took into account the degree of heritability of the traits, which in a number of cases can only be estimated approximately. And besides, all these forecasts are based on an assumption - which, incidentally, is quite unrealistic - that the way of life (including diet) and the selection factors acting on North American women will not change over ten generations.

**Are we degenerating?**
Persistent rumors circulate that humanity is threatened by genetic degeneration. Many journalists and philosophers assert this. And it must be admitted that these rumors did not arise without cause. Many scientists seriously consider this possibility. It seems we do indeed have grounds for concern.

The problem is that cultural, social, and scientific-technological progress leads to a weakening of purifying selection - the very selection responsible for weeding out harmful mutations. We are talking, above all, about so-called weakly deleterious mutations, each of which by itself does not lower viability and fertility very strongly, but when many of them accumulate, the cumulative effect becomes noticeable.

Humans, or other animals, burdened with a large number of weakly deleterious mutations, have poor health; they may have reduced immunity, intelligence, energy, reaction speed, fertility, lifespan, sexual attractiveness, and everything else for which "good genes" are needed. Weakly deleterious mutations arise in every generation, and if selection does not filter them out, they accumulate. Every newborn human probably carries in their genome about ten new weakly deleterious mutations that were not present in their parents.

To begin with, let us imagine a situation in which there is no selection at all. We said above that this never happens, but one can imagine anything one likes. Suppose we are trying to save an extinct species of animal, and we have only two individuals left: a male and a female. We cross them and get offspring - one son and one daughter (generation 1). Suppose that, for some reason, we cannot get more than one son and one daughter from a pair of parents. The son will have ten new weakly deleterious mutations, and the daughter will also have ten - but different ones. Now let us cross brother and sister: we simply have no other option if we want to preserve the species. Let us, for simplicity, ignore the harmful consequences of inbreeding (close-kin crossing). We obtain offspring - a girl and a boy. Each of them inherits, on average, half of each parent's harmful mutations (5 + 5 = 10), plus another ten new ones will appear. In total, in generation 2 each individual will have on average 20 harmful mutations. In generation 3 there will already be 30 mutations, and so on. Degeneration under such conditions (when there is no selection at all) occurs quickly and inevitably. Very soon we will get a generation so weak, sickly, and feeble that no ultra-modern medicine will help this pair produce offspring. Without selection, any species will quickly degenerate and perish. Simply because: 1) mutagenesis cannot be stopped; 2) most non-neutral mutations are harmful.

Genetic degeneration under conditions of weakened selection is not a purely theoretical construction, but an experimentally confirmed fact. In 1997 the well-known evolutionary biologist Alexey Kondrashov, now working at the University of Michigan, and his colleagues Lev Yampolsky and Svetlana Shabalina published the results of an experiment on fruit flies, in which selection in the studied populations was radically weakened (Shabalina et al., 1997). The authors took, from each pair of flies, one randomly chosen son and one randomly chosen daughter. Selection was thus not entirely abolished, because some pairs could not produce offspring at all, larvae did not hatch from some of the laid eggs, some larvae could not pupate, and adult flies did not emerge from some pupae. Evidently, this fate befell those whose genomes were too heavily burdened with harmful mutations. Nevertheless, selection became significantly weaker than in nature or in an ordinary laboratory population, where flies living in food-filled vials form pairs of their own choosing and compete freely for food and space. If selection is not switched off, it is quite capable of counteracting the harmful effects of inbreeding, as shown by the experience of breeding pure lines of laboratory animals, or, say, the history of the ancient Egyptian pharaohs, who regularly married their relatives.

After 30 generations, the experimental fly populations were in a deplorable state. Their fertility and lifespan had dropped sharply. Moreover, they had become sluggish and, in the words of A. S. Kondrashov, "did not even buzz." [I had an interesting discussion with A. S. Kondrashov about this on the internet, which can be found at: https://macroevolution.livejournal.com/36027.html (part 1) and https://macroevolution.livejournal.com/38950.html (part 2).] Genetic degeneration is obvious.

There is reason to believe that over the last 100 years humans (at least residents of developed countries) have found themselves in conditions similar to Kondrashov's experiment. Thanks to the development of medicine, the invention of antibiotics, the solving of the food problem, and the rise in the standard of living, mortality has fallen sharply (and, a little later, so has fertility). In developed countries almost every child born survives. Moreover, poor health has ceased to be a serious obstacle to reproduction (see the video recording of A. S. Kondrashov's public lecture "Evolutionary Biology of Man and Health Care": https://www.polit.ru/science/2010/10/22/kondrashov_live.html).

In Kondrashov's opinion, natural selection today acts on humans almost not at all, at least in developed countries. This means that people's survival and fertility have practically ceased to depend on their genotype.

Undoubtedly, the danger of the accumulation of harmful mutations in the human population exists. But what is the scale of the catastrophe? For precise estimates the data are still insufficient, but we nevertheless do have certain grounds for restrained optimism. I have already said that present-day data on the (albeit only partial) genetic conditioning of most behavioral traits do not allow one to believe in the possibility that human reproductive success no longer depends on genotype at all. Everything in us depends on genotype - kindness, intelligence, happiness in family life, even political views. And you're saying the expected number of offspring, reproductive success, does not depend on it? Unconvincing. For example, the trait "age at first childbirth" definitely has nonzero heritability and is under the action of selection (see above). Moreover, it undoubtedly depends on certain character traits, does it not? Including such traits for which hereditary variability exists (since practically all character traits have nonzero heritability). Therefore, human reproductive success, despite all the achievements of medicine, still depends on genotype. The efficiency of weeding out weakly deleterious mutations has, of course, decreased, but it has still not dropped to zero. A person burdened with a multitude of weakly deleterious mutations will on average be weaker, sicklier, less intelligent, less attractive (crookedly-warped - asymmetric). On top of everything, they will cost their parents more. If the case is very severe, it will make the parents think twice about whether it is worth having another child. Even if this weak, sickly person survives thanks to medicine and leaves offspring, that is not enough for selection to stop acting. Selection will only stop acting once such a person leaves, on average, exactly as many - down to fractions of a percent! - children as a healthy, strong, intelligent, attractive, symmetrical person who brought their parents nothing but joy (and so they wanted to have another one). Even if only by fractions of a percent, the reproductive success of people burdened in this way with a genetic load will, even in the most developed countries, still be lower than that of carriers of fewer weakly deleterious mutations. Selection has not stopped - it has merely become weaker, but it has not disappeared and will never disappear as long as we live in our biological bodies and have not turned into robots.

There is also direct factual confirmation of what has been said. For example, it has been established that the reproductive success of both men and women in modern industrial society correlates positively with external attractiveness. Americans born in the 1937-1940s, whose photographs at age 18 are rated by other people as more attractive, on average had more children than their less attractive peers. This is partly explained by sexual selection - attractive people less often remain unmarried - but it seems also by "ordinary" natural selection, that is, by a positive correlation between attractiveness and fertility. Interestingly, in women the dependence of reproductive success on attractiveness is nonlinear: the most offspring were left by women belonging to the "second quartile segment from the top" - that is, attractive, but not the most irresistibly beautiful. The great beauties bore more children than the women in the two "lower quartiles", but still fewer than the merely attractive women. What explains this - inflated self-esteem, concern for one's figure, or something else - is not yet known (Jokela, 2009).

Moreover, selection continues to work excellently at the level of embryos. A zygote (fertilized egg cell) excessively burdened with harmful mutations will not last long; it will be "culled" at the early stages of embryonic development. True, such selection also acted on the fruit flies in Kondrashov's experiments - and did not save the poor creatures from degeneration.

I place great hopes in the technology of in vitro fertilization (IVF), for which its creators recently received the Nobel Prize. The "test-tube conception" method involves creating several "spare" zygotes, which are grown to a certain (very early) stage of embryonic development, after which the healthiest of these embryos are selected for transfer into the uterus of the future mother. If we learn to carry out genetic analysis of embryos quickly and without harm to them, we will be able to weed out harmful mutations far more effectively than ordinary natural selection would.

Purifying selection has indeed become weaker, but perhaps we don't currently need it to be strong. The point is that the size of humanity today is unprecedentedly high: we are nearly seven billion. No species of terrestrial vertebrate of our size has ever had such numbers in the entire history of the Earth. There are limits to how much population size has the most direct relationship to the efficiency of selection acting on weakly deleterious mutations: the larger the population, the smaller the chance a weakly deleterious mutation has of spreading in the gene pool. Let us try to understand why this is so. First consider a small population of 1,000 individuals. Suppose half of these individuals carry in their genotype a weakly deleterious mutation that reduces reproductive success by 0.01% (one ten-thousandth) compared to carriers of the non-mutant allele of the same gene. A mutation with such a weak negative effect in a population of 1,000 individuals will simply be imperceptible to selection. Put simply, if there were 500 mutants in generation 1, then in generation 2 their number should decrease by 0.01%. What would this mean in practice? Let us try to calculate the average expected number of mutants in the second generation: 500 - (0.01 x 500/100) = 499.95. But the number of individuals cannot be a fraction. In reality we would get a whole number of mutants close to 500: it could be 482, or 512, or 501, or 497. The probability that there will turn out to be fewer than 500 mutants is slightly greater than the probability that there will be more than 500. However, this difference in probabilities will be negligibly small. In other words, this mutation in a population of 1,000 individuals will behave, in effect, as neutral. Its frequency will change according to the law of random walk, and in the end the mutation will either become fixed or be eliminated. The probability of fixation of the weakly deleterious mutation in this case will be close to 0.5, just as for any neutral mutation (at an initial frequency of 0.5). But if the population is large, say consisting of 7 billion individuals, then such a mutation will already be very noticeable to selection. Its frequency will decrease honestly by approximately 0.01% in each generation. If there were initially 50% mutants (3,500,000,000), then in the next generation there will be on average 350,000 fewer individuals (and not 0.05 individuals fewer, as in the previous case). Of course, in this case too there will be a random spread. However, the probability that, owing to chance, the number of mutants in generation 2 will turn out to be greater than in generation 1 will this time be not close to 50% (as it was in the small population), but close to 0%. The same holds for the probability of fixation (elimination). In a small population, the probability that the mutation will become fixed is close to 50%. In a large one - it is practically zero. So there you have the effect of population size. In a large population, even a mutation with a very weak negative effect will be weeded out by selection and will never be able to reach one-hundred-percent frequency. In a small one, by contrast, it can easily become fixed. Thus, the enormous size of humanity is in itself a good defense against the spread of weakly deleterious mutations.

Incidentally, the colossal size of the population, combined with the weakening of purifying selection, gives us additional chances for the appearance of very improbable (that is, rare) beneficial mutations. A mutation whose probability of arising is one in a billion will occur, in a population of 1,000 individuals, on average once every million generations. That is, effectively never. In a seven-billion population, such a mutation will almost certainly occur already in the first generation. As for the weakening of purifying selection, it gives us an additional chance to escape the so-called traps of local fitness maxima (see the chapter "Victims of Evolution"). To develop some valuable new adaptation, we may need to go through a stage of temporary decrease in fitness. For example, this may require three mutations in combination, where the first and second mutations are harmful by themselves, but in combination with the third they give a positive effect. Medicine now allows us to traverse such evolutionary trajectories, which are forbidden to populations under strong purifying selection, because it gives a chance of survival to promising mutants carrying the first two "harmful" mutations.

Moreover, no matter how powerful medicine becomes, no one has abolished, nor will anyone ever abolish, people's selectiveness in choosing a long-term sexual partner. There will always be super-princesses seeking super-princes, and there will always be citizens of lower "quality" forced to restrain their pickiness and choose partners roughly like themselves (such selectiveness, or "positive assortative mating", genuinely exists in humans when forming marital pairs, as it does in other monogamous animals). People burdened with a multitude of weakly deleterious mutations will tend to pair up mainly with one another, just as the lucky ones with good genotypes will. Such selectiveness, incidentally, sharply increases the efficiency of purifying selection. At one edge of the spectrum, completely non-viable weaklings will keep being born, time and again. They die at early stages of embryogenesis or a little later, taking their mutations with them.

Positive assortative mating by intelligence also exists in humans (intelligent women tend to choose intelligent men, and unintelligent men avoid interacting with women more intelligent than themselves). This allows us to hope that if we do become more foolish in the future, it will only be on average, not radically and not completely.

A few more considerations can be cited that allow us to hope that the accumulation of harmful mutations due to weakened selection may perhaps not pose such a great threat to humanity after all.

First, one must define what exactly we mean by "harmfulness". In evolutionary biology, a harmful mutation is a mutation that lowers fitness (reproductive success). The degree of harmfulness is determined by the magnitude by which this mutation lowers fitness. If a mutation does not lower fitness, then it is not harmful from an evolutionary point of view, even if its phenotypic effect is personally not to our liking. From this point of view, it must be acknowledged that the harmfulness of mutations is not constant: it changes depending on the development of medicine and other benefits of civilization.

For example, the high infant mortality of Homo sapiens was to a large extent caused by infections, from which we are now protected by antibiotics and vaccines. For illustration, let us consider a hypothetical harmful mutation that reduces resistance to the smallpox virus. Suppose this mutation increases the probability of falling ill with smallpox on contact with the virus, or increases the probability of death in the event of illness. Such a mutation was very harmful 200 years ago (let's assume it lowered fitness across humanity on average by 2%). When vaccination appeared, the harmfulness of this mutation decreased (let's assume it now lowers fitness by only 1%). And now, when the smallpox virus no longer exists in nature (this was solemnly announced in 1980), the harmfulness of this mutation has vanished entirely. The mutation has simply ceased to be harmful, whatever we might understand by "harmful". It has become neutral, and can now calmly undergo random fluctuations in its frequency under the action of drift.

Most diseases, of course, have not disappeared the way smallpox did. They can still kill a person, but thanks to the availability of antibiotics, the probability of such an outcome today is significantly lower than before. Mutations that increase susceptibility to all of these diseases used to lower fitness very strongly, and now their harmfulness has decreased. We could say that the purifying selection acting on these harmful mutations has weakened. But one can say the same thing in other words: these mutations have become less harmful.

It seems likely that many of the harmful mutations now accumulating in humanity's gene pool because of weakened selection are exactly of this kind - their harmfulness having been radically reduced thanks to medicine.

Unfortunately, in many cases evolutionary "harmfulness" does not coincide with human "harmfulness". Natural selection can only protect us from mutations that lower reproductive success. But it will not protect us from mutations that lower the quality of our lives without affecting the number of offspring left behind.

In the experiment with fruit flies, when two offspring from each female were kept alive, the experimenters, in effect, told the flies: "Dear flies, from now on, all mutations that reduce your fertility to ten, five, or even two offspring in a lifetime will no longer be harmful to you. However many you produce, exactly two will survive regardless." The flies rejoiced and quickly accumulated mutations that reduce fertility but are, under the conditions of the experiment, completely harmless to them. Then the experimenters came back and said: "Actually, we were joking. These mutations are still harmful after all, and we are now going to count them up. Oh, how degenerate you've become!"

Looking at the situation from this angle, one might note that, from an evolutionary point of view, the flies in this experiment perhaps had not degenerated all that much. But from the point of view of the flies themselves (had they possessed consciousness and been capable of a little reflection), their affairs really were bad. Their vital energy had vanished, their lifespan had shortened, they had become sluggish, and had even stopped buzzing. I'm afraid we too are not protected from all this. We won't die out, but we can quite plausibly become, on average, sicklier, more sluggish, and more foolish.

Moreover, it is entirely possible that this is precisely what has been happening to us over the last 10,000 years (since the transition from hunting and gathering to farming and pastoralism). Or even 40,000 years - since the Upper Paleolithic revolution.

It is a pity, of course, that we are not becoming kinder, more intelligent, and more talented from generation to generation. That is, not becoming so genetically; the development of culture is, for now, saving us. But still, one would like it to happen genetically too. Is there hope? Hard to say. Personally, I place great hopes on princesses. If only they don't turn promiscuous in their liaisons. Dear princesses! Please remember that political correctness is out of place when choosing a life partner. You deserve better. Watch the indicators of fitness closely. Do not confuse genuine large, beautiful, and costly peacock tails with cheap imitations.

And finally - one more encouraging, though purely hypothetical, consideration. How closely does the mortality rate correlate with the efficiency of selection? Yes, we know that nowadays people in developed countries have started having very few children, and almost all of these children survive, that is, postnatal mortality has fallen sharply. Should we conclude from this that the efficiency of postnatal selection has decreased by exactly the same amount? It seems to me: no, because there is another important variable: the degree to which mortality depends on genotype. Many individuals die or remain childless not because their genes are bad, but simply because they were "unlucky". In other words, there exists a certain variability in reproductive success among individuals, and the question is what fraction of this spread is determined by hereditary variability. It is obvious that this quantity is always less than 100% and always greater than 0%. The efficiency of selection depends on it no less than on the mortality rate.

In theory, as organisms transition from an r-strategy to a K-strategy (that is, from producing a great many poorly protected offspring to producing a small number of well-protected ones), the degree to which reproductive success depends on genes (rather than on chance) ought to increase. If this were not so, we would observe very sharp differences between r- and K-strategists in the rate of accumulation of harmful mutations, the rate of genetic meltdown, and species extinction. We would observe K-strategists dying out faster and, in the end, always losing out. After all, K-strategists by definition produce fewer offspring and have lower mortality. However, this is not observed. In the paleontological record we see many examples of how a transition to a K-strategy clearly improved a group's "genetic well-being" and evolutionary prosperity. In the evolution of terrestrial animals and plants there is a clear tendency toward the development of ever-better care for offspring, that is, a movement toward the K-strategy. And at the same time, average rates of species extinction, on the whole, do not rise but fall.

What is happening with humanity right now is a pronounced shift toward the K-strategy: fewer children are being born, but a great deal of resources is invested in each one, and almost all of them survive. Wasn't the high mortality of the past, including infant mortality, far more dependent on chance (rather than on genes) than it is now? Children died like flies, mainly from poor sanitation and malnutrition. Famine could engulf entire regions, epidemics of deadly diseases swept across continents. Doesn't this resemble the mass death of krill in a whale's maw, where almost nothing depends on the genotype of a particular crustacean?

Today, in developed countries, most people are more or less materially provided for, medicine is accessible to all, famine does not threaten, and the healthiest young men are not conscripted into 25-year military service. Doesn't this lead to a radical reduction in the influence of chance on reproductive success? And to an increase in the influence on it - however strange it may seem - of genes? If everyone is socially more or less equal (well, at least ideally) and the forces of nature no longer threaten you, then what else could your success, including reproductive success, depend on, if not on genes - over which no democracy and no political correctness yet holds sway, and which are still different in everyone? Perhaps the "equalization of chances" provided by civilization (as well as the intensified care for offspring and other characteristic features of the K-strategy) does not, in fact, decrease but rather increase the dependence of reproductive success on genotype? If so, it must contribute not only to a decrease in the efficiency of selection (through the reduction in mortality), but also to an increase in that efficiency (through the growing influence of genotype on reproductive success). Unfortunately, there is still not enough data to quantitatively assess all these hypothesized mechanisms. In the end it may well turn out that these listed "protective effects" are still not sufficient, and genetic degeneration will indeed become a serious problem for us after a few more generations. Not a lethal one, but a distasteful one. What is good and what is bad? As attentive readers have probably noticed, the author does not consider this question directly related to the subject of the book. In my view, it is not at all the business of biologists to decide which of our soul's evolutionarily determined (or culturally instilled) features should today be considered "good" and which "bad". All the more so since all of this changes so easily and quickly: both over time and from country to country, from community to community, even from family to family. In Europe and the US, crying on someone's shoulder is considered normal; in Korea, not so much. Lending money at interest was once considered immoral; now all banks do it with pride. Smiling at a stranger is considered indecent in some places, and the opposite elsewhere. Murder is a terrible sin, but in wartime, on the order of a superior - go right ahead. One could list such examples endlessly. Biological evolution has a rather indirect relation to all of this. Evolutionary psychology and anthropology answer a different question - they help us understand why we are the way we are. And they maintain a dead silence regarding how we should be, what we should strive for, and which patterns of behavior to take as a model. The data of these sciences can be compared to an etymological dictionary. It is interesting to read about the origin of words - it broadens one's horizons and even helps solve some special tasks - but it entails no organic conclusions concerning everyday language. If your goal is to learn to write and speak correctly, then knowledge of the Proto-Indo-European roots from which various words descend is unlikely to help you much. An orthographic dictionary and a grammar reference will be of far more use. Even more useful - conversing with educated people. The biological evolution of our psyche, evidently, is not yet complete, but it proceeds slowly. On time intervals of the order of a few centuries, it can generally be safely neglected. A far greater influence on the development of moral norms, laws, traditions, and styles of behavior has, for many millennia now (at least since the Upper Paleolithic), been exerted by cultural-social evolution. It is based on the selective reproduction of memes, not genes. It has its own laws, which we have hardly spoken of, since this book is devoted to the biological, not the cultural-social, evolution of humans. Evolution has provided us with a large brain in which, from birth, certain templates and preparations already exist that help it work with incoming information. We are not born with a virginally clean soul and an empty memory. The blank-slate hypothesis has long since been rejected by psychologists and neurobiologists. But these templates are plastic, and in different cultural environments the same innate predispositions may manifest in quite different ways. One and the same mutation affecting the level of oxytocin secretion may, in one cultural-social setting, foster friendship with the residents of a neighboring village, and in another - hostility toward them. But we also have innate predispositions that manifest in a similar way across the most diverse cultural surroundings. This does not mean their manifestations do not depend on culture at all. But it does mean that they depend little on the cultural differences that exist on the planet today. This, in turn, allows us to suppose that these templates manifested in a similar way in our Paleolithic ancestors too, and that this is precisely why they were favored by selection. Among such stable templates - behavioral stereotypes, probably advantageous to Paleolithic hunter-gatherers - are some that are quite decent by today's standards. For example, those innate predispositions of ours which, in many people, become embodied in a conscious moral principle - the ideal of reciprocal altruism, the golden rule of ethics: "Do unto others as you would have them do unto you." But these templates are very diverse, and at times contradict one another. We clearly have a genetic predisposition toward forming emotional attachment to a marital partner - and this, perhaps, stretches back to the times of early hominids who switched to monogamy. But we (unlike prairie voles) also have a clear tendency to easily rid ourselves of such attachments, "not to become their slaves". We have a predisposition toward marital infidelity, and certain properties that can be interpreted as adaptations aimed at preventing infidelity (jealousy, perhaps, is among them). All of this too most likely reaches us from very ancient times. What here is good, and what is bad? Evolutionary psychology modestly, but firmly, refrains from answering. Decide for yourself! And if you don't want to take responsibility upon yourself, you can shift it onto society in the person of its chosen representatives (friends, parents, neighbors, writers, TV hosts, popular performers - whoever you prefer). They will gladly explain to you how a decent girl ought to behave and what a worthy young man must do to earn universal respect. Like any person, I have my own ideas of good and evil. But they are not derived directly from the data of evolutionary psychology - and should not be. They are derived from the cultural riches accumulated by humanity, the realities of today, the state of society, and the atmosphere of one's social surroundings. For example, I cannot tolerate xenophobia in any of its manifestations, from Nazism to homophobia and ideological intolerance, even though I understand that the evolutionary roots of this repulsive psychic trait are quite deep and firm. The main thing is to understand that the evolutionary approach to humans justifies nothing and no one. It explains origins, and that is a different matter. I do not understand the logic of those citizens who believe that evolution supposedly justifies the merciless extermination of the weakest (this mistaken theory is known as "social Darwinism"), nor the logic of those who demand that the teaching of evolution be banned in schools on the pretext that "if children are told they descend from apes, the children will then behave like apes." Fantastic nonsense! By that logic, let's also hide from children the fact that they consist mostly of water, or they might start spreading out and taking the shape of their container. We did not descend from apes. We are apes, but special apes, cultural ones (in the sense that our behavior is determined by culture, not only by genes), and moreover intelligent ones, with as many as seven registers of short-term working memory. Why on earth should we take chimpanzees as our example - these relict forest hominids incapable of manufacturing a simple Oldowan flake? Even from our quite recent ancestors - Paleolithic hunter-gatherers, Bronze Age people, or medieval Europeans - if we take any example at all, we do so very selectively. And rightly so. Those folks considered "good" much of what today is unambiguous evil. To speak seriously, I believe that the desacralization and demystification of the human psyche, the exposure of its true evolutionary and neurobiological roots, is the path to raising our self-awareness to a new, higher level. Many believe that the chief distinguishing feature of a human being is the capacity for reflection, awareness of one's own existence. That is not enough. The next step must be awareness of one's own nature and origin. Frankly, I hope that one day the paradoxical phrase "man descends from Darwin" will be perceived as a banal truth. Our internal "model of self", this primordial foundation of our social intelligence, once finally cleansed of primitive fairy tales and frightful ghosts, as well as of an excessively inflated sense of self-importance, with the skeletons in its closets rewritten and accounted for, will become a far more effective working tool than the semi-finished product with which evolution released us into the world of culture. And it is precisely on the "model of self" that everything long considered good (even if in a narrow, "parochial" sense) is founded: mutual understanding, love, compassion. We will be able to understand each other better. We will be able to become more magnanimous. Yes, the ability to manipulate one's fellows is also based on this model, but try applying your Machiavellian tricks to a compatriot who knows Machiavellian tricks no worse than you do. Enough already of being victims of evolution, friends. Enough of feeling with our gut and thinking with our stomach. We have seven registers, we have not yet finally destroyed this planet, we have already understood where we came from, and we have already walked on the Moon. Things may still not turn out so badly after all. Grandeur It is a rare author of a popular book on evolution who can resist quoting the final phrase of Darwin's "Origin of Species." I too will not resist. Here it is: There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. As for the "Creator", he was not yet present in the first edition of the "Origin". In place of "the Creator breathed" there stood an impersonal construction. In subsequent editions Darwin not only added the word "Creator", but, under pressure from critics, introduced many other changes into the book that, from today's vantage point, look ill-advised. Someone even joked that the sixth edition would more accurately have been titled "The Origin of Species by Means of Natural Selection and a Great Many Other Different Means." The mention of the Creator added to the text bothered Darwin, judging by his letters. On the whole he leaned toward the idea that life could have originated on its own "in some warm little pond." But he had no arguments, and he decided to spare his reputation. Well, never mind - that's not the point. The point is the grandeur. It is simply astonishing how some people manage, to this day, not to notice the genuine grandeur, the breathtaking beauty of the scientific picture of the world. Including - already largely clarified thanks to the efforts of scientists - the history of our own biological species. Humanity, in its cultural development, has produced many captivating, talented, aesthetically appealing myths about the origin and structure of the world. I myself have loved them since childhood. These stories were selected for their ability to affect the psyche: the most striking ones were remembered and retold, the boring ones were forgotten. It's no wonder some of them possess a spellbinding, hypnotic effect. Having taken hold of the mind, they don't want to let it go. They are adapted precisely for this. The conclusions of science are not selected for their charming power. They are selected for their correspondence to the facts. It would seem that, for this reason alone, they should stand no chance of winning the competitive struggle of memes for control of mass consciousness. But it was not so. The picture of the world, gradually assembled from the discoveries of science, turns out to be exquisitely complex, harmonious, and grand. In a word, no less charming than the myths and legends specifically selected for that trait. Astonishing! Or perhaps not. Could a world that gave rise to such a pensive ape as Homo sapiens possibly turn out to be boring and unattractive? Fortunately, more and more people are coming to understand this. Here, for example, is a wonderful quote from the LiveJournal of the user zlata_gl (published with the author's permission): I was prompted to this topic by a conversation with people who are proud that God Himself created them. So I declare: I am proud of my glorious ancestors! I am proud of the ape that thought of picking up a stone and cracking a nut with it. Maybe it had bad teeth... This is a very complex operation for the volume of an ape's brain. At the very limit of its capabilities. The equivalent, for us, of a Newton or an Einstein. It is necessary to combine three objects in one place: the stone on which the nut is placed, the stone with which it is struck, and the nut itself. I am proud of the Pithecanthropus who first approached the terrifying beast - fire, the terror of all animals. He took a burning branch in his hand and carried it. And began to feed the fire with other branches. His courage is comparable to the exploits of all the heroes of historical times. I am proud of the Neanderthal who was the first to start caring for a wounded compatriot or comrade. We know of him from the excavations at Shanidar, where the remains of people who lived long after severe wounds were found. One of them was disabled, missing an arm and an eye. No animal could have survived with such injuries. I am proud of the Cro-Magnons who painted the walls of caves with pictures of deer hunts. And of the Neolithic people who cast seeds into the ground. Their real feats are higher and more interesting than all the miracles of religious mythology. The same must be said of the mysteries of the human soul, uncovered by neurobiology and experimental psychology. They have turned out to be far more interesting and profound than any mystical fantasies. More interesting, if only because they can genuinely be discovered. They can be tested by facts and experiments, rather than simply invented and taken on faith. Deeper - if only because any mysteries of a mystical character, if traced to their foundation, very quickly run into some "causeless first cause" or other absurdity and unknowability. At first this is mesmerizing, but soon it becomes tedious. Networks of billions of neurons, among which there are more connections than there are stars in the Galaxy, mesmerize far more strongly, once you begin to make sense of them. Science does not kill the soul. It uncovers it, and even, in a certain sense, creates it. And moreover - it takes it by the hand and leads it out of the kindergarten with its fairy-tale pictures on the walls, into the majestic and beautiful world of reality.