Maximum load g. Force units

On the one hand, it helps to clear the gene pool of harmful mutations that make up the “ge-no-ti-che-th load”, on the other hand, it can lead to the extinction of the species. It depends on the nature of sexual selection. If it negatively affects the adaptability of the species, then this leads to extinction. And if, as in the case of humans, it will only eliminate the genetic load, then the role of sexual selection will be extremely positive.

No matter how exalted and unearthly love feelings seem to us, in fact, pre-reading and and in relation to each other are largely rational. And even such a seemingly strange selection criterion, as, in fact, is perfectly explained. Moreover, it should be noted that sexual selection also affects the rate of evolution in the same way. And in the case of humans, sexual selection is the only method of selection. This is due to the development of technology. People are more practical-ti-ches-ki not subject to eu-test-ven-no-mu selection,. Now everyone survives, and that's good. But many of the "survivors" leave offspring, and this is bad.

Due to the fact that almost all people, regardless of their health, can leave offspring, the human gene pool is deteriorating. This is not a call to become "childfree". This is a statement of fact. We as a species have stopped weeding out negative mutations through natural selection. And that's bad! And the only humane solution to this problem is development, capable of correcting without sacrifice what nature corrects with cruelty. But so far, in the case of humans, weeding out negative mutations occurs only through sexual selection. And therefore, in our case, he plays an exceptionally-key-chi-tel-but-lo-zhi-tel-tion role. Though for it also it is necessary to pay bitter youthful tears.

The Negative Role of Sexual Selection

In the case of animals in constant danger of being brutally killed and eaten, the role of sexual selection may not be so positive. This is due to the fact that an increase in con-ku-ren-to-spo-behavior-nos-ti in sexual selection can adversely affect survival. Individuals can adapt worse to natural conditions. This is clearly seen on the ex-pe-ri-men-tah with fish -. Females prefer brighter or spotted males, so in the absence of predators, males become very attractive. If a predator is launched into the aquarium, then after several generations the males will become less bright. This is due to the role of the EU-test-ven-no-go and sexual selection.

The brightest males will be eaten by predators, so they will not leave offspring or leave, but less, as a result of which their mutations are gradually eliminated. The dimmest males will not undergo sexual selection, so their genome will also not be widely represented in the population. Therefore, the most common phenotype will be something in between. But in this case, the role of sexual selection is obviously negative. Instead of letting the males adapt-tee-ro-wa-xia, the females force them to stay bright, resulting in a smaller fish population than it could be. And, in the end, such sexual selection can shorten the life span of the entire species. Therefore, do not follow the example of fish, and love each other not for brightness, but for content!

Sources

www.nlm.nih.gov/pmc/articles/PMC1070813/

www.nlm.nih.gov/pmc/articles/PMC3151377/

www.nlm.nih.gov/pmc/articles/PMC2702796/

www.nlm.nih.gov/pmc/articles/PMC3684741/

www.nlm.nih.gov/pmc/articles/PMC1691857/

Nature.com/articles/s41586-018-0020-7

www.nlm.nih.gov/pmc/articles/PMC5319324/

www.nlm.nih.gov/pmc/articles/PMC5290736/

www.nlm.nih.gov/pmc/articles/PMC3210352/

www.nlm.nih.gov/pmc/articles/PMC4394296/

ncbi.nlm.nih.gov/pmc/articles/PMC3721656/

www.nlm.nih.gov/pmc/articles/PMC3193187/

academic.oup.com/beheco/article/14/2/194/192089

sciencedirect.com/science/article/pii/S000334729690010X

www.nlm.nih.gov/pmc/articles/PMC3141438/

www.nlm.nih.gov/pmc/articles/PMC3797706/

sexual selection - the form natural selection, based on the rivalry of individuals of the same sex for mating with individuals of the opposite sex. At the same time, the fitness of a genotype (phenotype) is assessed not by its survival rate, but by its participation in reproduction. The value of sexual selection lies in the activation of the process of reproduction of the species. There are two forms.

In the first form of selection the female is passive, and the males fight for the right to continue the race, and the stronger one wins. In this direction, the male in a number of generations increased physical strength, activity, hooves, horns, fangs, spurs (in roosters), etc. developed more powerfully.

With the second form the female is active, which chooses a more attractive male for procreation, which has led to competition between males for a more beautiful and bright outfit (most birds and butterflies). For each male, this can cause death, but for the population as a whole it has positive value, as it increases the chances of these males to prolong the genus.

The concept of sexual selection explains the origin of many traits that, at first glance, are useless or even harmful to both the individual and the species. These signs include:

• strong branching of the antlers of deer, weakening their importance as organs of defense or attack,
• a long heavy tail in males of some birds during the mating season.

Sexual selection is progressive form of selection, since the "struggle" between males does not raise the question of survival, of the struggle for the conditions necessary for life (food, living space, etc.). Therefore, sexual selection does not require the death of the "losers": the "losers" usually survive and may be even more durable than the winners, and in the subsequent mating season they may turn out to be "winners".

Sexual selection has played a significant role in human evolution. The fundamentals of the concept of sexual selection were developed by C. Darwin (The Origin of Man and Sexual Selection, 1871).

Natural selection is divided into individual and group . Individual selection is reduced to the differential reproduction of individual individuals that have advantages in the struggle for existence within populations. Individual selection is based on the competition of individuals within populations.

Natural selection, "processing" insignificant hereditary differences of individuals and "folding" them in a certain direction, contributes to the gradual deviation of descendants from their ancestors. Any features and properties of species and larger taxa are formed in the process of selecting individuals based on their assessment. individual differences. Against this constant background of individual selection in nature, group selection is carried out - the predominant reproduction of individuals of any group.

At group selection in evolution, traits favorable for the group, but not always favorable for individuals, can be fixed. In group selection, groups of individuals compete with each other to create and maintain integrity over organismal systems.

Related individuals have a greater similarity of genotypes than unrelated ones. Therefore, if some trait in a part of related individuals contributes to the survival of their neighbors, then such a trait can be fixed in evolution even if it has a negative effect on the immediate carrier. For example, an individual that warns its relatives with a cry about the appearance of a predator, most often turns out to be a victim of the attacker. However, all other individuals of this group will be saved, and since the altruistic trait is characteristic of at least some of them too, this trait will be spread by natural selection (selection of relatives). It is assumed that it group selection fixed in the evolution of the properties associated with the regulation of population size. Group selection can lead to the displacement of one of the competing groups and thus to a decrease in group diversity, or to the emergence of new differences between forms and thereby to a decrease in selection pressure. Observations have shown that species of African savannah antelopes eat different parts of herbaceous plants (some eat only the soft tops of grasses with flowers, others only dry grass straws, others eat thorny leaves, etc.). This situation is the result of group interspecific selection, which contributes to an increase in the "sum of life" per unit area.

In all cases, without exception, group selection based on intrapopulation natural selection. This is understandable, since the competition of species in the process of evolution is carried out through the competition of their individuals. The emergence of evolutionary innovations occurs only with individual selection, while group selection selects from ready-made adaptations that have arisen at the intraspecific level. Intermediate position is occupied group intraspecific selection- selection different families, populations, groups of populations.

sexual selection

a form of natural selection in animals based on the rivalry of individuals of one sex (mainly male) for the possession of individuals of the other sex, leading to a decrease in the offspring of the less adapted. As a result of sexual selection, secondary sexual characteristics (bright mating coloration, horns, etc.) arose in many animal species.

sexual selection

special form natural selection, which determines the emergence in the process of evolution of secondary sexual characteristics. These features include: the bright mating color of the plumage of ducks, black grouse and many other birds, the “dancing” of insects, the display of birds, the “tournament fights” of male birds and mammals, the various sound signaling of males, which serves to attract females, odorous glands to attract individuals opposite sex in insects, mammals, etc. Sharply distinguished characters (coloration, etc.) develop mainly in males; females (especially during the breeding season), as a rule, are more protected by protective coloration and shape, appropriate behavior, etc. The primary basis for the action of P. o. there was a discrepancy in identifying features male and female. This probably facilitated the encounters of heterosexual individuals of the same species and prevented interbreeding with individuals of other species. Subsequently, individuals with more pronounced sexual characteristics attracted individuals of the other sex more easily, which led to their predominant reproduction. By. ≈ one of the factors determining the development of ethological (behavioral) mechanisms of isolation. Sometimes P.'s action about. conflicts with the action of other directions of natural selection: genotypes are preserved that increase the success of reproduction, but do not increase the viability of the species as a whole. However, this circumstance does not give grounds to oppose P. o. natural selection and consider it an independent factor in evolution. P.'s concept about. put forward and substantiated by C. Darwin (1859, and especially 1871). See also Indirect selection, Sexual dimorphism.

Lit .: Darwin Ch., The origin of species by means of natural selection, trans. from English, Soch., vol. 3, M. ≈ L., 1939; his, The Origin of Man and Sexual Selection, trans. from English, ibid., vol. 5, M., 1953; Shmalgauzen I.I., Problems of Darwinism, 2nd ed., L., 1969.

A. V. Yablokov.

Wikipedia

sexual selection

sexual selection- a process based on competition for a sexual partner between individuals of the same sex, which entails selective mating and the production of offspring. This mechanism may cause the evolution of some characteristic features and lead to their enhancement. Within a species, one of the sexes (almost always female) plays the role of a limited resource for the other (almost always male).

Sexual selection is a special case of natural selection.

Some modern ethologists are of the opinion that the feeling of love and self-sacrifice is the result of sexual selection and inbreeding selection at the genetic level.

Selection at the level of a single gene, hitherto regarded as an overly simplistic but useful abstraction, seems to have been a real and even the main selective process on early stages organic evolution, when gene-like particles were the predominant unit of organization. In the modern world, there is a process that is close to selection at the gene level - the differential reproduction of viral particles or bacterial cells that differ in one viral or bacterial gene.

Some genetically controlled deviations of meiosis in Drosophila melanogaster lead to the fact that one of the chromosomes of a homologous pair is included in more efficiently functioning spermatozoa than the other. The disturbed splitting of chromosomes in meiosis leads to an increase in the frequency of a chromosome of one type in the gamete fund compared to the frequency of its homologue. This process is known as the meiotic drive. Similar frequency changes are observed in genes located on these two homologous chromosomes and in phenotypes determined by these genes. In one case, the sex ratio changes towards an excess of females, in the other case, the frequency of one recessive lethality increases (Sandler and Novitski, 1957; Hiraizumi, Sandler, and Crow, 1960). The meiotic drive is essentially a process of differential reproduction of homologous chromosomes, i.e., selection at the chromosome level.

In flowering plants, male gametes are found in independent structure The male gametophyte consists of pollen grains and a pollen tube. A heterozygous plant produces genetically different classes of pollen; in some cases, pollen grains are broken down by genetic factors that affect the viability of the pollen, its ability to germinate, or the growth rate of the pollen tubes. In addition, pollen is usually produced and deposited on the stigma in large quantities than is needed for fertilization, so that there is competition between pollen grains or pollen tubes. When pollen is degraded for growth factors, this competition results in some classes of male gametes being more efficient than others at fertilization, and therefore more likely to contribute to the formation of embryos or endosperm, i.e., selection occurs at the level of gametes. .

Let us assume that some marker gene that determines a certain outwardly noticeable morphological trait, linked to the gene that determines the growth of the pollen tube. In this case, among the descendants, instead of the expected Mendelian splitting for this gene, a deviant ratio will be observed: an excess among seeds or seedlings morphological type determined by the allele-marker introduced by pollen, selectively superior to the pollen of another class, and a decrease in the proportion of the opposite morphological type. The change in ratios during splitting, due to the low selective value of certain classes of pollen, is well known in different types flowering plants.

The case of linked genes Su (which determines the type of endosperm) and Ga (which controls the growth of the pollen tube) in maize has been well analyzed ( Zea mays). Su/su heterozygotes usually produce grains that are divided into two classes (starchy and sugary endosperm) in Mendelian ratios according to the nature of the endosperm. Assume that the su allele (sugary endosperm) is linked to the ga allele (pollen tube slow growth) in a heterozygote (Su Ga/su ga) and that heterozygote is used as the paternal individual, so that the su-ga linkage is transmitted through the pollen. In this case, in the next generation, there is a noticeable shortage of grains of the sugary type (Mangelsdorf and Jones, 1926).

sexual selection

Sexual selection is based on the selective inequality of individuals of the same sex in dioecious organisms (usually in animals). This is a special form of individual selection in which representatives of only one sex (usually males) of a given population participate.

Sexual selection begins with the "division of labor" between gametes and between their carriers, which arose on early stages evolution of sexual reproduction. The specialization of the eggs and ultimately the females was to provide nourishment and protection to the embryo, while the specialization of the spermatozoa and ultimately the males was to locate the eggs and fertilize them. This separation of functions led at the outset to a numerical predominance of spermatozoa over eggs, to a greater motility of spermatozoa or males compared to eggs or females, and to the development of a stronger sex drive in males than in females. All this laid the foundation for the emergence of selective differences between males.

Sexual dimorphism in animals is often expressed in differences in two groups of characters. Primary sexual characteristics are those that are directly related to reproduction. Here we will not consider them. Males have secondary sexual characteristics that help them find mating partners. It is to these secondary sexual characteristics that the theory of sexual selection is addressed.

Secondary sexual characteristics can be divided into two broad classes: 1) signs relating to size, strength and various kinds of appendages (for example, larger males in sea lions or antlers in male deer); 2) decorations and display behavior (for example, bright plumage of drakes, bright spots on the neck of male hummingbirds, special types songs, marital behavior). In The Descent of Man and Sexual Selection, Darwin (1871) reviewed examples of secondary sexual characteristics known in his time in male animals belonging to a wide range of groups, and proposed the theory of sexual selection to explain them.

Darwin conceived of sexual selection as a process complementary to the more general and more widespread process of natural selection. The latter, according to Darwin's theory, created the adaptive characteristics of this species as a whole, including the original adaptations common to both sexes, as well as primary sexual differences directly related to reproduction. Natural selection in its original Darwinian sense did not explain secondary sex characteristics. Characters such as deer antlers or the bright plumage of drakes are not adaptations favorable to the species as a whole; nor are they necessary for reproduction. However, they appear to increase the likelihood of mating success for those males that possess them. The theory of sexual selection was introduced in order to explain the development of such special male traits.

Darwin describes the process he proposed as an explanation as follows (Darwin, 1871): "... sexual selection ... depends on the advantages, relating exclusively to reproduction, that some individuals have over other individuals of the same sex and species." He further explains (I have paraphrased Darwin's statement here, retaining his terminology): if both sexes lead exactly the same way of life, but the male's sense organs or organs of locomotion are much more developed than those of the female, then it is possible that males often manage to acquire these traits not because they are better adapted to survive in the struggle for existence, but because they have certain advantages over other males in breeding. “In such cases, sexual selection must have come into play.”

The study of sexual selection since 1871 has been going on winding way. In Darwin's time, this topic was a matter of controversy. Wallace (1889) assumed the role of sexual selection in the development of traits required by males in fights, but not in the development of display traits. Then this problem was consigned to oblivion. When, at the beginning of the modern period of evolutionary research, it reappeared on the scene in the works of Fisher (Fisher, 1930) and Huxley (Huxley, 1938), the situation was quite different: the same phenomena were considered from other alternative points of view, and the theory of sexual selection should have been debut again. This second debut turned out to be successful: at present, sexual selection is the subject of active research and an extensive literature is dedicated to him.

In order to evaluate state of the art problems of natural selection, one should first of all clearly imagine the huge variety of secondary sexual characteristics that carry the most different functions in animal life. The emergence of all these characters, apparently, cannot be attributed to the selection of any one type. Differences in overall size between males and females may be due to selection for ecological divergence (see part ) as well as sexual selection. Powerful horns and other "weapons" of males can serve to seize territory or achieve a dominant position in the community, as well as to conquer females. Various kinds of decorations, displays, songs, and the smell of males can serve as courtship stimulants and species-specific identification signals. AT last case they may have arisen through selection for reproductive isolation (see part ), as well as through sexual selection.

The emergence of the entire vast spectrum of secondary sexual characteristics is the result of the combined action of various selective processes, so it is difficult to single out the effects of sexual selection alone here.

AT last years attempts are being made to extend the concept of sexual selection to dioecious plants. These attempts are expressed in the interpretation known facts biology of plant reproduction in terms of a greatly extended concept of sexual selection. In particular, they indicate a very large number of pollen grains compared to the number of eggs and the resulting competition between these grains (Stephenson and Bertin, 1983; Willson, 1983). However, this state of affairs is the result of the original division of labor between males and females; it is an indispensable prerequisite for the process of sexual selection, as already mentioned, and not its result. The phenomenon of incompatibility in plants, some types of pollen which successfully germinate only in a certain ovule, is considered as a choice on the part of the female (Stephenson and Bertin, 1983; Willson and Burley, 1983). In this case, the concept of such a choice is expanded, covering the immunological reactions of organisms deprived of nervous system or mental capacity. Intermale selection is theoretically possible in dioecious plants. However, this problem is currently far from being solved due to the lack of a critical approach, as well as the necessary data.

Signs of males associated with fights between them

The role of sexual selection is clearly expressed in the development of traits associated with fights between males and with the phenomenon of dominance. Three conditions are necessary for sexual selection of this type: 1) competition between males for females; 2) genotypic differences between males, which determine their competitiveness in the fight for females; 3) the reproductive advantage of successful males over other males.

The first condition exists in mammals and birds with a polygynous (polygamous) breeding system. In polygynous species, the strongest males gather harems of females around them and guard the females themselves or the territory in which they are located, driving away the weaker males, so that few or no females remain for the share of the latter.

Polygyny is common in mammals and occasionally in birds. Among mammals, it occurs in deer, cattle, sheep, most antelope, elephants, seals, sea lions, walruses and baboons; among birds, chickens, pheasants, and peacocks. The males of these animals have well-developed secondary sexual characteristics, in contrast to the males of related non-polygyn groups. So, in polygynous chickens, pheasants and peacocks, males are much larger, more pugnacious, and their plumage is more elegant than that of females, while in monogynous - gray partridge, grouse and tundra partridge - the differences between individuals of different sexes are relatively small. In walruses and sea lions, the males are very large; males of many ungulates are decorated with horns; in baboons, males are large and aggressive. In contrast, in monogynous wolves and some monogynous monkey species, as well as in a number of cats whose cubs are raised mainly by the mother, and in colonial but non-polygynous rodents, males and females almost do not differ from each other in size and strength (Darwin , 1871, chapter 8).

Since the signs associated with fights between males are observed mainly in polygynous groups, we can assume that they arose as a result of sexual selection. The correlation between overall size dimorphism and the mating system is less clear, not to mention numerous exceptions and complications (Ralls, 1977).

In mammals and birds, another correlation is also observed - between the mating system and the contribution of parents to the care of offspring (Trivers, 1972; Zeveloff and Boyce, 1980).

In birds, males and females take more or less equal part in various aspects of caring for offspring, i.e., in building a nest and rearing chicks. The breeding strategy common to most birds necessitates the cooperation of both parents. This leads to monogamy, which is widespread in birds. In monogamy, when each male has a marriage partner, there is no competition between males for females. Accordingly, the traits necessary for males in fights and for gaining a dominant position do not develop either.

Polygynous, male-dominated birds are the exception that proves the rule.

In mammals, the reproductive strategy is based, on the contrary, on the predominant role of the mother in caring for offspring, which is due to the bearing of the embryo in the womb and feeding the cub with her own milk. The contribution of males to the care of offspring is often negligible. Freed from this care, males get the opportunity to compete for females and arrange harems. This sets the stage for sexual selection for traits associated with male dominance, which are often found in mammals. Monogamous mammals, with their equality between the sexes, are the exception that proves the rule.

Reproductive Behavior in Bighorn Sheep and Red Deer

Sexual selection will only be effective if the winning males leave more surviving offspring than the unsuccessful males (condition 3 in the previous section). Information about the relative breeding success of individual males in natural conditions difficult to obtain and few in the literature. However, there are now more such data, and we will give two examples here.

Clutton-Brock et al. (1982), who studied red deer for a long time ( Cervus elaphus) in Scotland obtained data on the reproductive success of individual individuals. This species is characterized by pronounced sexual dimorphism. Males weigh almost twice (on average 1.7 times) more than females. During the autumn rut, fights occur between males, the outcome of which is determined by the overall size, strength and size of the horns of males. The winners collect harems for themselves, and the number of females in the harem varies from 1 to 22, depending on the fighting qualities of the male, and the defeated remain lonely.

Successful males cover several or many females each breeding season, while unsuccessful ones sometimes do not mate at all. In a sample of 13 males, the number of surviving offspring per male (for his entire life) ranged from 0 to 25. This number correlates with the size of the harem, which, as we have seen, depends on the fighting qualities of males. It is clear that the differences between males in terms of reproductive success are very large (Clutton-Brock et al., 1982).

Signs that determine the attractiveness of males

Much less clear is the role of sexual selection in the development of male display traits, such as ornaments, singing, and pheromones, in non-polygistic groups of animals. These traits can be given various explanations, not necessarily related to sexual selection. In addition, there are problems regarding the adequacy of the selective mechanism itself. Sexual selection for traits associated with male ornamentation and display behavior implies a purely individual selection by females, and this is a factor that cannot be quantified.

Do females prefer the most attractive or strongest males, and are they consistent in their preferences? And in non-polygyn animals, in which the number of females and males is the same and they form mating pairs, will females that mate with males whom they immediately preferred to all others leave more offspring than those who had to choose a second time? Sexual selection for traits that determine the attractiveness of males would be effective if all or most females preferred males of one type, but is this condition fulfilled in nature? What happens if females differ in their preferred type of male? If for all or for most females of a given species there is the same standard of attractiveness for males, then how did this standard for the whole species arose in the first place?

Some recent studies have found an association between female preferences and the reproductive success of males of the chosen type. butterflies Colias (C. eurytheme and C. philodice) females make a choice between males based on flight kinetics. Preferred males reach greatest success in mating and, apparently, also possess best ability flight (Watt et al., 1986). At the frog Physalaemus pustalosus in Panama, females prefer certain type sound signals. Males that make such calls are more likely to mate. These successfully mating males are also older and larger, so in this case, just like butterflies Colias fitness seems to play a role (Ryan, 1980; 1983; 1985). Goby females Cottus bairdi prefer to mate with large males, with successful mating females laying more viable eggs (Downhower et al., 1983). In these and similar cases, the choice of females is based on a trait associated with the general fitness of the males.

Such cases do not allow us to explain the vast class of male display traits, which, it would seem, do not give their owners any advantages and may even have a detrimental effect on their viability. It is generally accepted that the long tails of some male birds of paradise reduce their fitness. The mating calls of male Panamanian frogs increase the likelihood of their destruction by predators - bats (Trachops cirrhosus) (Tuttle and Ryan, 1981).

There is reason to doubt that the mechanism of sexual selection can and does create highly conspicuous and non-adaptive male display traits. The emergence of this class of features can, however, be explained by another combination of selective forces, the action of which is composed of a series of successive stages. Initially, such display traits are favored by ordinary individual selection, promoting courtship and mating. Specific display characters and courtship rituals within a given species could probably have racial characteristics, such as local dialects in some bird species. Racial differences should cause some initial reproductive isolation. Further divergence at the species level should generally reinforce this ecological isolation and its underlying traits as a by-product of such divergence. Finally, the display characters and courtship rituals of divergent species must be further differentiated by selection for ethological isolation per se, in order to suppress interspecific hybridization (see part ).

This hypothesis is consistent with the great role played by the display traits of the male and the choice on the part of the female in ethological isolation. The choice of a mating partner by a female essentially concerns interspecific relations no less than intraspecific ones. Females usually accept males of their own species, but reject males with display traits of a foreign species. In short, the presence of non-adaptive display traits in males can be explained as a result of speciation.

The relationship between ethological isolation, speciation, and sexual selection has recently been noted in fish of the family Cichlidae from African lakes and in the group Drosophila sitvestris from the Hawaiian Islands (Dominey, 1984; Carson, 1986; Mayr, 1988). These authors consider sexual selection to be the driving force in the development of ethological isolation and speciation. This explanation is consistent with the facts. Equally, however, it can be considered that the main determining factor is speciation, as described above. In general, it does not seem to me necessary to invoke sexual selection in the strict sense to explain precisely these and other similar cases.

Inter-dem selection

Let us now turn to the question of selection for population level causing great controversy. Interdemic selection, often also called group selection, is the differential breeding of different local populations. We begin by looking at interdemean selection in organisms that do not form communities.

One of the features organic world, which is difficult to explain on the basis of individual selection, but can be considered as the result of interdemic selection, is sexual reproduction. Although models have been created in which sexual reproduction is favored by individual selection (Williams, 1975), they do not appear to be realistic. sexual reproduction is the process that creates recombination variation in breeding populations. It is not the parental genotypes that break up in the process of recombination that benefit from sexual reproduction, but the population of future generations, in which the margin of variability increases. This implies participation as one of the factors in the selective process at the population level.

Social group selection

Social hymenoptera are one of the examples of the extremely high integration of communities in the animal world, and the effects of social-group selection are very pronounced in them. Selection of this type probably also operates in groups with a less highly integrated community structure, such as birds and mammals. In Part VIII we will try to show that some features of the species Homo sapiens may have arisen as a result of social group selection.

Altruism

The altruistic behavior of animals is made up of a variety of specific features behavior. In general, it can be defined as behavior that benefits other individuals. Its range is very wide - from behavior favorable to other individuals in a moderate degree, to genuine self-sacrifice, up to suicide. Altruistic behavior may benefit offspring, other relatives, or social groups.

Existence various types altruistic behavior suggests that different types selection. Let's consider three cases.

The first case is the altruistic behavior of parent individuals towards their offspring. This type of altruistic behavior can be attributed to the general phenomenon of caring for offspring in birds and mammals, or special types of behavior characteristic of lapwings, noisy plover and other earth-nesting ones, which pretend to be injured, distracting the attention of the predator, or take it away from the nest. Care for offspring is clearly the result of individual selection, since individual selection favors the preservation of the genes of those parents that leave the largest number of surviving offspring.

Consider now the connection with self-sacrifice defensive behavior worker individuals in social bees, such as Apis mellifera. When a worker bee uses a sting, it is tantamount to suicide for her, but beneficial for the colony, as it prevents the enemy from invading. Colonies that defend better than others survive and reproduce more successfully than colonies with less effective defense. Self-sacrifice of worker bees, along with other characteristics of the worker caste, can be adequately explained as the result of social group selection, since it benefits the bee colony as a whole.

The third case is groups of primitive people who are at the stage of gathering and hunting, an example of which is the Bushmen of southwestern Africa (Lee and Devore, 1976). These communities are organized groups, which includes family members, other relatives, relatives, and sometimes random guests from other groups. The custom of sharing food is deeply rooted in them. If a large animal is killed, its meat is distributed to all members of the group, regardless of whether they are relatives or casual visitors. Other types of cooperative behavior also develop in such groups.

Suppose now, by way of discussion, that the distribution of food and other similar types social behavior have some genetic basis; this will allow us to try to study the types of selection that may be involved in the development of such behavior.

The individual selection favoring the development of care for offspring is probably very intense. It is difficult to imagine, however, that members of a community share food only with their descendants, while depriving other members of the community and close relatives, since the behavioral phenotype and "social pressure" from other members of the group usually have plasticity. Primates leading a social way of life are not characterized by rigid and strictly directed types of behavior. Behavior related to the distribution of food should naturally go beyond its original goals, i.e., the supply of food to offspring, and extend to the whole family and kindred group. It should also be expected that social-group selection should contribute to the development of such behavior. The group as a whole depends on the association of its members in foraging activities that essentially ensure survival, and it must benefit from the distribution of food on a broad basis. The tendency to share food, reinforced by social group selection, should extend to all members of the group, both blood relatives and "in-laws" in equally. Such behavior probably overlaps with the types of behavior created as a result of individual selection among relatives of the intermediate rand. In short, the distribution of food could be adequately explained as the result of the combined action of individual and social-group selection aimed at creating plastic cultural traditions.

Kin selection

The term kin-selection was coined by Maynard Smith (1964). The most appropriate link is given (scanner's comment) ")">*), defining it as a selection aimed at preserving traits that favor the survival of close relatives of a given individual. Such relatives can be either the descendants of a given individual, or its siblings and other relatives. As examples of traits resulting from kin-selection, he cited care for offspring, imitation of injury, and sterile worker castes in social insects.

Maynard Smith and later researchers consider kin-selection to be a process close to social-group selection, and possibly intermediate between individual and group selection.

Kin selection has gained popularity as a concept and term and is very widely used in the literature. However, I believe that it does not explain much, but it can cause a lot of confusion in thinking (see Grant, 1978). Partly kin-selection is a later synonym for individual selection aimed at developing care for offspring, and partly a later synonym for group selection.

The phenomena attributed to kin-selection are quite explicable by these other types of selection, i.e. individual selection for the care of offspring, or social-group selection, or joint action these two processes.

Some authors prefer the term kin selection to the old term group selection because it emphasizes the role of kinship. However, kinship is deeply embedded in the concept of group selection. All social groups animals is related groups. There is no need for a separate term - kin-selection.

Can we find any phenomena in nature that are determined by kin-selection in a narrow sense, excluding such previously accepted types of selection as individual selection and social-group selection? Some of the phenomena usually attributed to kin-selection, such as altruism and worker castes in social insects, have already been discussed. Another set of traits, warning coloration in non-edible insects, has for some time been thought to be the result of kin selection.

The predator kills an insect that has a warning color, finds that it is inedible, and learns to recognize the color signal. This benefits the sibs of the dead insect, which have the same coloration. The kin selection explanation for warning coloration comes from the assumption that a predator kills non-edible insects when it tries to eat them. Wiklund and Jarvi (1982) tested this assumption in experiments on a large number of warning insects, which they presented to four bird species. It turned out that birds usually do not kill the insect. They "try" it, reject it, and often (in 84% of the samples) the insect remains alive. Therefore, inedibility and warning coloration are quite understandable on the basis of individual selection alone (Wiklund and Jarvi, 1982).

Selection at the species level

At least three types of selection operate at the species level: 1) selection aimed at developing ecological divergence; 2) substitution of species; 3) selection leading to reproductive isolation. These types of selection are discussed in part , but they are listed here just to complete our review.

The possibility of selective processes at the level of biotic communities was also discussed. It has been argued that more stable communities may outlast less stable ones on ecological time scales (MacArthur, 1955; Hutchinson, 1959; Dunbar, 1960). * 17