V.A. Geodakyan
Evolutionary theory of sex
NO ONE natural phenomenon did not generate as much interest and did not contain as many mysteries as gender. The problem of sex was dealt with by the greatest biologists: C. Darwin, A. Wallace, A. Weissman, R. Goldschmidt, R. Fischer, G. Meller. But mysteries remained, and modern authorities continued to talk about the crisis of evolutionary biology. “Sex is the main challenge to modern evolutionary theory... the queen of problems in evolutionary biology,” says G. Bell. “The intuitions of Darwin and Mendel, which illuminated so many mysteries, could not cope with the central mystery of sexual reproduction.” Why are there two genders? What does this give?
The main advantages of sexual reproduction are usually associated with ensuring genetic diversity, suppressing harmful mutations, and preventing inbreeding. However, all this is the result of fertilization, which also occurs in hermaphrodites, and not differentiation (separation) into two sexes. In addition, the combinatorial potential of hermaphroditic reproduction is two times higher than that of dioecious reproduction, and the quantitative efficiency of asexual methods is two times higher than that of sexual ones. It turns out that the dioecious method is the worst? Why then are all evolutionarily progressive forms of animals (mammals, birds, insects) and plants (dioecious) dioecious?
The author of these lines, back in the early 60s, expressed the idea that gender differentiation is an economical form of information contact with the environment, specialization in two main aspects of evolution: conservative and operational. Since then, it has been possible to discover a number of patterns and create a theory that explains common positions many different facts and predicts new ones. The essence of the theory will be presented in the article.
Two genders, two flows of information
In principle, two solutions to this conflict are possible for the system: to be at some optimal “distance” from the environment or to split into two coupled subsystems, conservative and operational, the first “to be moved away” from the environment in order to preserve the existing information, and the second “to be brought closer” to the environment for getting a new one. The second solution increases the overall stability of the system, therefore it is often found among evolving, adaptive, tracking systems (regardless of their specific nature), biological, social, technical, etc. This is precisely the evolutionary logic of sex differentiation. Asexual forms “adhere” to the first solution, dioecious forms to the second.
If we distinguish two flows of information: generative (transfer of genetic information from generation to generation, from the past to the future) and ecological (information from the environment, from the present to the future), then it is easy to see that the two sexes participate in them differently. In the evolution of sex, at different stages and levels of organization, a number of mechanisms appeared that consistently ensured a closer connection of the female sex with the generative (conservative) flow, and the male sex with the ecological (operational) flow. Thus, the male sex, compared to the female sex, has a higher frequency of mutations, less additivity of inheritance of parental characteristics, a narrower reaction norm, higher aggressiveness and curiosity, more active search, risky behavior and other qualities that “bring closer to the environment.” All of them, purposefully placing the male sex on the periphery of distribution, provide him with preferential receipt of environmental information. Another group of features is the huge redundancy of male gametes, their small size and high mobility, greater activity and mobility of males, their tendency to polygamy and other ethological and psychological properties. Long periods Pregnancy, feeding and caring for offspring in females, actually increasing the effective concentration of males, turn the male sex into “surplus”, therefore, “cheap”, and the female into scarce and more valuable.
This leads to the fact that selection operates mainly due to the exclusion of male individuals; “redundancy” and “cheapness” allow it to work with large coefficients. As a result, the number of males in the population decreases, but their greater potential allows them to fertilize all females. A small number of males transmit as much information to their offspring as big number female, in other words, the channel of communication with offspring is wider for males than for females. This means that the genetic information transmitted through the female line is more representative, but through the male line it is selective, i.e., in the female line the past diversity of genotypes is more fully preserved, while in the male line the average genotype changes more strongly.
Let's move on to the population of an elementary evolving unit. Any dioecious population is characterized by three main parameters: sex ratio (the ratio of the number of males to the number of females), sex dispersion (the ratio of the variance values of a trait, or its diversity, in males and females), sexual dimorphism (the ratio of the average values of a trait for males and females). floors). Attributing a conservative mission to the female sex and an operational one to the male sex, the theory connects these population parameters with environmental conditions and the evolutionary plasticity of the species.
In a stable (optimal) environment, when there is no need to change anything, conservative tendencies are strong and evolutionary plasticity is minimal. In a driving (extreme) environment, when it is necessary to increase plasticity, operational tendencies intensify. In some species, say lower crustaceans, these transitions are carried out by switching from one type of reproduction to another (for example, in optimal conditions parthenogenetic, in extreme dioecious). In most dioecious species, this regulation is smooth: under optimal conditions, the main characteristics decrease (the birth rate of males falls, their dispersion narrows, sexual dimorphism decreases), and under extreme conditions they increase (this environmental rule differentiation of sexes).
Since environmental stress leads to their sharp growth, these population parameters can serve as an indicator of the state of the ecological niche. In this regard, it is significant that the birth rate of boys in Karakalpakstan has increased by 5% over the past decade. According to environmental rule, the main parameters should increase during any natural or social disasters (major earthquakes, wars, famine, relocations, etc.). Now about the elementary step of evolution.
Transformation of genetic information in one generation
A genotype is a program that in different environments can be realized into one of a whole range of phenotypes (traits). Therefore, the genotype does not contain specific value characteristic, but a range of possible values. In ontogenesis, one phenotype is realized, the most suitable for a particular environment. Consequently, the genotype sets a range of realizations, the environment “selects” a point within this range, the width of which is the reaction norm, characterizing the degree of participation of the environment in determining the trait.
For some characteristics, such as blood type or eye color, the reaction norm is narrow, so the environment does not actually affect them; for other psychological ones, intellectual abilities very broad, so many associate them only with the influence of the environment, i.e. upbringing; third characteristics, say height, mass, occupy an intermediate position.
Taking into account two differences between the sexes in the reaction rate (which is wider in females) and the cross-section of the communication channel (wider in males), we will consider the transformation of genetic information in one generation, i.e. from zygotes to zygotes, in becoming a bilizing and driving environment. Let us assume that the initial distribution of genotypes in the population is the same for male and female zygotes, i.e., there is no sexual dimorphism for the trait in question. In order to obtain from the distribution of zygote genotypes the distribution of phenotypes (organisms before and after selection), from it, in turn, the distribution of egg and sperm genotypes, and, finally, the distribution of zygotes of the next generation, it is enough to trace the transformation of two extreme genotypes of zygotes into extreme phenotypes, extreme gametes and again into zygotes. The remaining genotypes are intermediate and will remain so in all distributions. The wider reaction norm of the female sex allows it, due to modification plasticity, to leave the selection zones, preserve and transmit to the offspring the entire spectrum of the original genotypes.
The narrow reaction norm of the male sex forces him to remain in the zones of elimination and undergo intense selection. Therefore, the male sex transmits to the next generation only a narrow part of the original spectrum of genotypes, which best corresponds to the environmental conditions at the moment. In a stabilizing environment this is the middle part of the spectrum, in a driving edge of the distribution. This means that the genetic information transmitted by the female sex to the offspring is more representative, and that transmitted by the male sex is more selective. Intensive selection reduces the number of males, but since the formation of zygotes requires an equal number of male and female gametes, males have to fertilize more than one female. The wide cross-section of the male channel allows this. Consequently, in each generation of the population, eggs of a wide variety, carrying information about the past richness of genotypes, merge with sperm of a narrow variety, the genotypes of which contain information only about the ones most suitable for current environmental conditions. Thus, the next generation receives information about the past from the maternal side, and about the present from the paternal side.
In a stabilizing environment, the average genotypes of male and female gametes are the same, only their variances differ, therefore the genotypic distribution of zygotes of the next generation coincides with the initial one. The only result of sex differentiation in this case comes down to the population paying for environmental information"cheaper" male gender. The picture is different in the driving environment, where changes affect not only variances, but also the average values of genotypes. Genotypic sexual dimorphism of gametes arises, which is nothing more than a recording (fixation) of environmental information in the distribution of male gametes. What is his future fate?
If paternal genetic information is transmitted stochastically to sons and daughters, at fertilization it will become completely mixed and sexual dimorphism will disappear. But if there are any mechanisms that prevent complete mixing, some of this information will pass from fathers only to sons and, therefore, some of the sexual dimorphism will be preserved in zygotes. But such mechanisms exist. For example, only sons receive information from the genes of the Uchromosome; Genes appear differently in offspring, depending on whether they are inherited from the father or mother. Without such barriers, it is also difficult to explain the dominance of the paternal genotype in offspring from reciprocal crosses, known in animal husbandry, for example, the high milk yield of cows transmitted through a bull. All this allows us to believe that only gender differences in the reaction rate and the cross-section of the communication channel are sufficient for genotypic sexual dimorphism to arise in the driving environment already in one generation, which will accumulate and grow as generations change.
Dimorphism and dichronism in phylogeny
So, when the stabilizing environment becomes driving for a given trait, the evolution of the male trait begins. gender, but in the female it remains, that is, the divergence of the character occurs, from monomorphic it turns into dimorphic. From several possible evolutionary scenarios, two obvious facts allow us to choose the only one: both sexes evolve; There are both mono and dimorphic traits. This is only possible if the phases of the evolution of the trait in the sexes are shifted in time: in the male, the change in the trait begins and ends earlier than in the female. Moreover, according to the ecological rule, the minimum dispersion of a trait in a stabilizing environment expands with the beginning of evolution and narrows at its completion.
The evolutionary trajectory of the trait bifurcates into male and female branches, and sexual dimorphism appears and grows. This is the divergent phase in which the rate of evolution and dispersion of the trait is male. After many generations, the variance in the female sex begins to expand and the trait begins to change. Sexual dimorphism, having reached its optimum, remains constant. This is a parallel phase: the rates of evolution of the trait and its dispersion in both sexes are constant and equal. When the trait reaches a new, stable value in the male sex, the variance narrows and evolution stops, but still continues in the female sex. This is the convergent phase in which the rate of evolution and dispersion is greater in the female sex. Sexual dimorphism gradually decreases and, when the trait becomes the same in the sexes, disappears, and the variances level out and become minimal. This completes the dimorphic stage of evolution of the trait, which is again followed by the monomorphic, or stability stage
Thus, the entire phylogenetic trajectory of the evolution of a trait consists of alternating monomorphic and dimorphic stages, and the theory considers the presence of dimorphism itself as a criterion for the evolution of the trait.
So, sexual dimorphism for any trait is closely related to its evolution: it appears with its beginning, persists while it continues, and disappears as soon as evolution ends. This means that sexual dimorphism is a consequence not only of sexual selection, as Darwin believed, but of any kind: natural, sexual, artificial. This is an indispensable stage, a mode of evolution of any trait in dioecious forms, associated with the formation of a “distance” between the sexes along the morphological and chronological axes. Sexual dimorphism and sexual dichronism are two dimensions of the general phenomenon of dichronomorphism.
The above can be formulated in the form of phylogenetic rules of sexual dimorphism and sex dispersion: if there is population sexual dimorphism for any trait, then the trait evolves from the female to the male form; if the dispersion of a trait is greater in the male sex, the divergent phase, the dispersion is equal to parallel, the dispersion is greater in the female sex, the convergent phase. According to the first rule, one can determine the direction of evolution of a trait, and according to the second, its phase, or the path traveled. Using the rule of sexual dimorphism, a number of easily testable predictions can be made. Thus, based on the fact that the evolution of most vertebrate species was accompanied by an increase in size, it is possible to establish the direction of sexual dimorphism in large forms males are generally larger than females. Conversely, since many insects and arachnids have become smaller during evolution, in small forms the males should be smaller than the females.
The rule can be easily tested on farm animals and plants whose artificial evolution (selection) was directed by humans. Selection of economically valuable traits should be more advanced in males. There are many such examples: in meat breeds of animals - pigs, sheep, cows, birds - males grow faster, gain weight and give best quality meat; stallions are superior to mares in sports and working qualities; rams of fine wool breeds produce 1.52 times more wool than sheep; Male fur-bearing animals have better fur than females; male silkworms produce 20% more silk, etc.
Let us now move from the phylogenetic time scale to the ontogenetic one.
Dimorphism and dichronism in ontogenesis
If each of the phases of the phylogenetic scenario is projected onto ontogeny (according to the law of recapitulation, ontogenesis is a brief repetition of phylogeny), we can obtain the corresponding six (three phases in the evolutionary stage and three in the stable; pre-evolutionary, post-evolutionary and inter-evolutionary) different scenarios for the development of sexual dimorphism in individual development. Dichronism will manifest itself in ontogenesis as an age-related delay in the development of a trait in the female sex, i.e., the dominance of the female form of a dimorphic trait at the beginning of ontogenesis and the male form at the end. This is an ontogenetic rule of sexual dimorphism: if there is population sexual dimorphism for any trait, during ontogenesis this trait changes, as a rule, from the female to the male form. In other words, the characteristics of the maternal breed should weaken with age, and the paternal breed should strengthen. Testing this rule against two dozen anthropometric characteristics completely confirms the prediction of the theory. A striking example development of horns in different types deer and antelope: the stronger the “hornedness” of a species, the earlier in ontogenesis horns appear, first in males and then in females. The same pattern of age-related developmental delay in females based on functional asymmetry of the brain was revealed by S. Vitelzon. She examined the ability of 200 right-handed children to recognize objects by touch with their left and right hand and found out that boys already at 6 years old have a right-hemisphere specialization, and girls up to 13 years old are “symmetrical.”
The described patterns refer to dimorphic, evolving characters. But there are also monomorphic, stable ones, in which sexual dimorphism is normally absent. These are fundamental characteristics of the species and higher ranks of generality, such as multicellularity, warm-bloodedness, a body plan common to both sexes, the number of organs, etc. According to the theory, if their variance is greater in the male sex, then the phase is pre-evolutionary, if in the female sex it is post-evolutionary . In the last phase, the theory predicts the existence of “relics” of sexual dimorphism and gender dispersion in pathology. The “relic” of dispersion manifests itself as an increased frequency of congenital anomalies in the female sex, and the “relic” of sexual dimorphism in their different directions. This is the teratological rule of sexual dimorphism: congenital anomalies of an atavistic nature should appear more often in the female sex, and those of a futuristic nature (search) in the male sex. For example, among newborn children with an excess number of kidneys, ribs, vertebrae, teeth, etc. of all organs that have undergone a reduction in number during evolution, there should be more girls, and with their shortage of boys. Medical statistics confirm this: among 2 thousand children born with one kidney, there are approximately 2.5 times more boys, and among 4 thousand children with three kidneys there are almost twice as many girls. This distribution is not accidental; it reflects the evolution of the excretory system. Consequently, three kidneys in girls is a return to the ancestral type of development, an atavistic direction; one kidney in boys is futuristic, a continuation of the reduction trend. The statistics for the anomalous number of edges are similar. Five-six times more girls than boys are born with dislocated hips, a birth defect that makes children better at running and climbing trees than healthy ones.
The picture is similar in the distribution of congenital heart defects and great vessels. Of the 32 thousand verified diagnoses, all “female” defects were dominated by elements characteristic of the embryonic heart or human phylogenetic predecessors: an open foramen ovale in the interatrial septum, a non-closed botal duct (the vessel connecting the fetal pulmonary artery to the aorta), etc. “Male” the defects were more often new (search): they had no analogues either in phylogeny or in embryos various kinds stenosis (narrowing) and transposition of the great vessels.
The listed rules cover dimorphic characteristics inherent in both sexes. What about traits that are characteristic only of one sex, such as egg production and milk yield? Phenotypic sexual dimorphism for such traits is of an absolute, organismal nature, but hereditary information about them is recorded in the genotype of both sexes. Therefore, if they evolve, there must be genotypic sexual dimorphism in them, which can be found in reciprocal hybrids. Based on such characteristics (among other evolving ones), the theory predicts the direction of reciprocal effects. In reciprocal hybrids, according to the divergent characteristics of the parents, the paternal form (breed) should dominate, and according to the converging characteristics, the maternal form. This is the evolutionary rule of reciprocal effects. It provides an amazing opportunity to reveal greater genotypic advancement of the male sex, even based on purely female characteristics. This seemingly paradoxical prediction of the theory is fully confirmed: in the same breed, bulls are genotypically “more productive” than cows, and roosters are more “egg-laying” than hens, i.e. these traits are transmitted predominantly by males.
Problems of evolution mainly refer to "black boxes" without entering into them direct experiment is impossible. Necessary information evolutionary doctrine drew from three sources: paleontology, comparative anatomy and embryology. Each of them has significant limitations, since it covers only part of the characteristics. The formulated rules give new method for evolutionary studies on absolutely all characteristics of dioecious forms. Therefore, the method is of particular value for the study of human evolution, such characteristics as temperament, intelligence, functional asymmetry of the brain, verbal, spatial-visual, creative abilities, humor and other psychological properties, to which traditional methods not applicable.
Functional asymmetry of the brain and psychological characteristics
For a long time it was considered a human privilege, associated with speech, right-handedness, self-awareness, and it was believed that asymmetry is a secondary consequence of these unique human characteristics. It has now been established that asymmetry is widespread in placental animals; most researchers also recognize the difference in its severity in men and women. J. Levy believes, for example, that the female brain is similar to the brain of a left-handed man, that is, less asymmetrical than that of a right-handed man.
From the perspective of gender theory, more asymmetrical brains in men (and the males of some vertebrates) mean that evolution moves from symmetry to asymmetry. Sexual dimorphism in brain asymmetry offers hope for understanding and explaining differences in the abilities and inclinations of men and women.
It is known that our distant phylogenetic ancestors had lateral eyes (in human embryos early stages development, they are located in the same way), the visual fields did not overlap, each eye was connected only with the opposite hemisphere (contralateral connections). In the process of evolution, the eyes moved to the front side, the visual fields overlapped, but for a stereoscopic picture to arise, visual information from both eyes had to be concentrated in one area of the brain. Vision became stereoscopic only after additional ipsilateral fibers emerged that connected the left eye to left hemisphere, right with right. This means that the ipsilateral connections are evolutionarily younger than the contralateral ones, and therefore in men they should be more advanced, i.e. there are more ipsilateral fibers in the optic nerve.
Since three-dimensional imagination and spatial visual abilities are associated with stereoscopy (and the number of ipsi-fibers), they should be better developed in men than in women. Indeed, psychologists are well aware that in understanding geometric problems men are far superior to women, as in reading maps, orienteering, etc.
How did psychological sexual dimorphism arise, from the point of view of gender theory? There is no fundamental difference in the evolution of morphophysiological and psychological or behavioral traits. The wide norm of reaction of the female sex provides it with higher plasticity (adaptability) in ontogenesis than that of the male sex. This also applies to psychological signs. Selection in zones of discomfort in males and females goes in different directions: thanks to a wide reaction norm, the female sex can “get out” of these zones due to education, learning, conformity, i.e., in general, adaptability. For the male sex, this path is closed due to the narrow norm of reaction; only resourcefulness, quick wits, and ingenuity can ensure his survival in uncomfortable conditions. In other words, women adapt to the situation, men get out of it by finding a new solution, discomfort stimulates the search.
Therefore, men are more willing to take on new, challenging, and extraordinary tasks (often doing them in rough drafts), while women are better at solving familiar problems to perfection. Is this why they excel in jobs that require highly polished skills, such as assembly line work?
If mastery of speech, writing, or any craft is considered in an evolutionary aspect, we can distinguish the phase of search (finding new solutions), mastery and the phase of consolidation and improvement. A male advantage in the first phase and a female advantage in the second was revealed in special studies.
Innovation in any business is the mission of the male gender. Men were the first to master all professions, sports, even knitting, in which women's monopoly is now undeniable, was invented by men (Italy, 13th century). The role of the avant-garde belongs to men and exposure to certain diseases and social vices. It is the male sex that is more often susceptible to “new” diseases, or, as they are called, diseases of the century; civilization, urbanization, atherosclerosis, cancer, schizophrenia, AIDS, as well as social vices: alcoholism, smoking, drug addiction, gambling, crime, etc.
According to the theory, there should be two opposing types of mental illness, associated with the vanguard role of the male gender and the rearguard role of the female gender. Pathology, which is accompanied by insufficient brain asymmetry, small size of the corpus callosum and large anterior commissures, should be two to four times more common in women, anomalies with the opposite characteristics in men. Why?
If there are no differences between the sexes in a quantitative trait, then the distribution of its values in the population is often described by a Gaussian curve. The two extreme regions of such a distribution are the zones of pathology “plus” and “minus” deviations from the norm, into each of which male and female individuals fall with equal probability. But if sexual dimorphism exists, then in each sex the trait is distributed differently, and two curves are formed, separated by the amount of sexual dimorphism. Since they remain within the general population distribution, one zone of pathology will be enriched in males, the other in females. By the way, this also explains the “sexual specialization” of many other diseases that is characteristic of the population of almost all countries of the world. The above examples show how the theory of gender “works” only in some human problems; in fact, it covers a much larger array of phenomena, including the social aspect.
Since the dimorphic state of a trait indicates that it is on the “evolutionary march,” the differences in the most recent evolutionary acquisitions of man—abstract thinking, creative abilities, spatial imagination, and humor—should be maximum; they should predominate in men. Indeed, outstanding scientists, composers, artists, writers, and directors are mostly men, and there are many women among the performers.
The problem of gender affects very important areas of human interest: demography and medicine, psychology and pedagogy, the study of alcoholism, drug addiction and crime; through genetics it is connected with economics. Correct social concept gender is needed to solve problems of fertility and mortality, family and education, and professional guidance. Such a concept must be built on a natural biological basis, because without understanding the biological, evolutionary roles of the male and female sexes, it is impossible to correctly determine them social roles.
Here are presented only a few general biological conclusions of the theory of sex; various previously incomprehensible phenomena and facts are explained from a unified position; prognostic possibilities are mentioned. So, let's summarize. The evolutionary theory of sex allows:
predict the behavior of the main characteristics of a dioecious population in stable (optimal) and driving (extreme) environments;
differentiate evolving and stable traits;
determine the direction of evolution of any trait;
establish the phase (traveled path) of the evolution of the trait;
define average speed evolution of the trait: V= dimorphism / dichronism
predict six different variants of the ontogenetic dynamics of sexual dimorphism corresponding to each phase of phylogeny;
predict the direction of dominance of the paternal or maternal breed trait in reciprocal hybrids;
predict and reveal “relics” of sex dispersion and sexual dimorphism in the field of congenital pathologies;
establish a connection between age and sex epidemiology
So, the specialization of the female sex in preserving genetic information, and the male sex in changing it, is achieved by the heterochronic evolution of the sexes. Consequently, sex is not so much a method of reproduction, as is commonly believed, but a method of asynchronous evolution.
Since the work presented here is the fruit of theoretical reflections and generalizations, it is impossible not to say a few words about the role of theoretical research in biology. Natural science, according to famous physicist, laureate Nobel Prize R. Millikan, moves on the two legs of theory and experiment. But this is how things are in physics, while in biology the cult of facts reigns, it still lives by observations and experiments, theoretical biology as such, there is no analogue of theoretical physics. Of course, this is due to the complexity of living systems, hence the skepticism of biologists who are accustomed to following the traditional path from facts and experiments to generalizing conclusions and theory. But can the science of living things continue to remain purely empirical in the “age of biology,” which, as many contemporaries recognize, is replacing the “age of physics”? I think it’s time for biology to stand on both legs.
The principle of coupled subsystems
The theory is based on the principle of coupled subsystems that evolve asynchronously. Male gender is operational subsystem of the population, female gender - conservative subsystem. New information from the environment first reaches the male sex and only after many generations is transmitted to the female, therefore the evolution of the male sex precedes the evolution of the female. This time shift (two phases evolution of a trait) creates two forms of the trait (male and female) - sexual dimorphism in the population. Evolutionary “distance” between subsystems is necessary to search for and test innovations.
The interpretation of sexual dimorphism as a phylogenetic “distance” between the sexes, as evolutionary “news” that has already entered the male subsystem, but has not yet been transferred to the female one, is applicable for all traits of plants, animals and humans in which sexual dimorphism is observed. Only in the case of species characteristics does the pattern appear in the area of pathology, population characteristics - in the norm, and for sexual characteristics - in the form of a “paternal effect”.
The theory relates the main characteristics of a dioecious population: sex ratio, gender dispersion And sexual dimorphism, with environmental conditions and evolutionary plasticity of the population. In optimal, stable environmental conditions, these characteristics are minimal, that is, the birth rate (at the same time the mortality rate) of boys decreases, their diversity and the difference between the male and female sexes are reduced. All this reduces the evolutionary plasticity of the population. IN extreme conditions, when rapid adaptation requires high evolutionary plasticity, reverse processes occur: the birth rate and mortality rate (that is, the “turnover rate”) of the male sex and its diversity simultaneously increase, and sexual dimorphism becomes clearer.
Analysis of the gender problem
The concept of gender includes two fundamental phenomena: sexual process(fusion of genetic information of two individuals) and sexual differentiation(dividing this information into two parts). Depending on the presence or absence of these phenomena, the many existing methods of reproduction can be divided into three main forms: asexual, hermaphroditic and dioecious. The sexual process and sexual differentiation are different phenomena and, in essence, diametrically opposed. The sexual process creates a variety of genotypes, and this is the advantage of sexual methods over asexual methods, recognized by many scientists. Sexual differentiation, by imposing a ban on same-sex combinations (mm, lj), on the contrary, reduces it by half (a phenomenon known in English literature as the “two-fold cost of sex”). That is, during the transition from hermaphroditic to dioecious reproduction, at least half of the diversity is lost.
Then, it is not clear what the division into two sexes gives if it halves the main achievement of sexual reproduction? Why are all species of animals that are progressive in evolutionary terms: (mammals, birds, insects) and plants (dioecious) dioecious, while there are clear advantages of quantitative efficiency and simplicity in asexual forms, and diversity of offspring in hermaphrodite ones?
To solve the riddle of dioeciousness, it is necessary to explain what differentiation gives, and for this it is necessary to understand the advantages of dioeciousness over hermaphroditism. This means that dioeciousness, which they try in vain to understand as the best method of reproduction, is not such at all. It's effective way of evolution.
Conservative-operative specialization of sexes
The division into two sexes is a specialization in preserving and changing information in a population. One sex should be informationally more closely connected with the environment, and be more sensitive to its changes. Increased male mortality from all environmental factors allows us to consider it operational ecological subsystem of the population. The female gender, as more stable, is conservative subsystem and preserves the existing distribution of genotypes in the population.
In the evolution of sex, at different stages and levels of organization, a number of mechanisms appeared that consistently ensured a closer connection of the female sex with the generative (conservative) flow, and the male sex with the ecological (operational) flow. Thus, in males, compared to females, the frequency of mutations is higher, the inheritance of parental characteristics is less additive, the reaction norm is narrower, aggressiveness and curiosity are higher, search activity is more active, risky behavior and other qualities that “bring closer to the environment.” All of them, purposefully placing the male sex on the periphery of distribution, provide him with preferential receipt of environmental information.
Another group of features is the huge redundancy of male gametes, their small size and high mobility, greater activity and mobility of males, their tendency towards polygamy and other ethological and psychological properties. Long periods of pregnancy, feeding and caring for offspring in females, actually increasing the effective concentration of males, turn the male sex into “surplus”, therefore, “cheap”, and the female into scarce and more valuable.
As a result of the conservative-operative specialization of the sexes, their asynchronous evolution occurs: new characteristics first appear in the operational subsystem (male sex) and only then enter the conservative (female sex).
The male gender remains in hazardous areas and is subject to selection. After the action of selection, the proportion of male individuals decreases and their genotypic dispersion narrows. In the driving environment, transformations affect both sex variances and average trait values: the reaction norm creates temporary, phenotypic sexual dimorphism, selection - genotypic. The male sex receives new environmental information. An increase in male mortality increases the male birth rate due to negative feedback.
The evolutionary role of sex chromosomes and sex hormones
The sexual process and sexual differentiation operate in opposite directions: the first increases the diversity of genotypes, and the second worsens it at least twice. Therefore, calling a “different” pair of homologous chromosomes (XY, ZW) “sex” just because they determine sex is not entirely correct. There are much more reasons to consider them “anti-sex”, since it is they who worsen the main achievement of sex - the combinatorics of characteristics. The main role of sex chromosomes is evolutionary - the creation of two time-shifted forms (female and male) for economical evolution.
The sex of the zygote is determined at conception by sex chromosomes. Further, until the end of ontogenesis, sex is controlled by sex hormones. In mammals, the base sex is homogametic (XX) - female; and the derived sex is heterogametic (XY) - male. It is triggered by the Y chromosome, which converts the “asexual” gonadal primordia of the embryo into testes that produce androgens. In the absence of the Y chromosome, the same tissues become ovaries, which produce estrogens. In birds, the base sex is also homogametic (ZZ), but male; and the derived female sex has a heterogametic constitution (ZW). It is triggered by the W chromosome, which turns the buds into ovaries that produce estrogens. In the absence of the W chromosome, the same tissues turn into testes that produce androgens. That is, in mammals, androgens move males away from females towards the environment, and in birds, estrogens move females away from males and the environment. In both cases, the male gender is “environmental”, and the female is “systemic”. Sex hormones determine the development of not only signs of sexual differentiation (sexual dimorphism), but also asymmetry of the brain, hands and other parts of the body (lateral dimorphism). Estrogens, expanding the reaction norm, allow female phenotypes to leave the selection zone and persist. They act “centripetally”, removing and isolating the system from the environment. Androgens, their chemical antagonists, act, on the contrary, “centrifugally”, bringing the system closer to the environment, exposing it to more intense selection and accelerating evolution. Consequently, the androgen-estrogen ratio regulates the intensity of information contact of the system with the environment.
Wider female reaction norm
The evolutionary theory of sex considers increased male mortality as a beneficial form of information contact with the environment for the population, carried out through the elimination of a part of the population by a harmful environmental factor. For example, all “new” diseases, diseases of the “century” or “civilization” (heart attack, atherosclerosis, hypertension, etc.), as a rule, are diseases of the male gender.
“Turnability” of males in extreme environmental conditions
In changing, extreme environmental conditions, male mortality increases and the tertiary sex ratio of the population decreases. The more changeable the environment, the fewer males remain in the population and, at the same time, the more of them are required for adaptation. It is possible to compensate for a decrease in the tertiary sex ratio only by increasing the secondary one. In other words, under extreme environmental conditions, both the mortality and birth rates of male individuals will simultaneously increase, that is, their “turnover” will increase.
Regulation of population sex ratio
Organismal mechanisms for regulating sex ratio
Negative Feedback is realized in plants through the amount of pollen, and in animals - through the intensity of sexual activity, aging, affinity and death of gametes. At the same time, a small amount of pollen, intense sexual activity of males, fresh sperm and old eggs should lead to an increase in the birth rate of males.
Population mechanisms of sex ratio regulation
To implement the population mechanism, it is necessary that the probability of having an offspring of a given sex differs among different individuals and is determined by their genotype. At the same time, there should be an inverse relationship between the reproductive rank of a given individual and the sex of its offspring: the higher the reproductive rank, the more offspring of the opposite sex there should be. In this case, regulation can be carried out at the population level - by greater or lesser participation in the reproduction of individuals that produce an excess of males or females in their offspring.
“Cross section” of the channel for transmitting information to offspring
Father and mother pass on approximately the same amount of genetic information to each offspring, but the number of offspring to which a male can pass on genetic information is incomparable more quantity, to whom the female can convey information. Each male, in principle, can transmit information to the entire offspring of the population, while females are deprived of this opportunity. That is, the capacity - the “cross section” - of the communication channel between the male and the offspring is much greater than the cross section of the female’s communication channel.
“Cross section” of the communication channel and the reproductive structure of the population
In a strictly monogamous population, the number of fathers and mothers is equal, that is, males and females have the same “channel cross-section” of communication with the offspring. In the case of polygyny, when there are fewer fathers than mothers, males have a larger “cross section” of the communication channel. In the case of polyandry, the opposite is true.
Ontogenetic and phylogenetic plasticity
A wide reaction norm makes the female sex more changeable and plastic in ontogenesis. It allows females to leave zones of elimination and discomfort, gather in a comfort zone and reduce phenotypic variance and mortality.
The male's narrower reaction norm does not allow him to reduce phenotypic variance. Males remain in zones of elimination and discomfort and die or do not leave offspring. This allows the population to new information“pay” is primarily a victim of males.
The high ontogenetic plasticity of the female sex provides it with high stability in phylogenesis. Over the course of generations, the female sex more fully preserves the existing distribution of genotypes in the population. The genotypic distribution of males varies much more. Consequently, in phylogenetic terms, the male sex is more changeable and plastic, and in ontogenetic terms, on the contrary, the female sex is more plastic and changeable. This, at first glance paradoxical, distribution of roles in phylogeny and ontogenesis, in fact, consistently and consistently implements the idea of specialization of the sexes according to the conservative and operational tasks of evolution.
Sexual dimorphism
Sexual dimorphism in one generation
Stable environmental conditions
In a stable environment, all transformations of genetic information affect gender variances, but do not affect the average values of traits. Therefore, there is no sexual dimorphism. There is only a difference in variance, which disappears when moving to the next generation. However, it is necessary that genotypic sexual dimorphism in the reaction norm exists in advance (in a stable phase), and genetic information about the broad reaction norm should be transmitted only through the female line, and about the narrow reaction rate only through the male line.
Changing Environment
In the driving environment, the phenotypic distribution of the male sex, before the action of selection, approximately repeats the original genotypic distribution. A wide norm of reaction of the female sex leads to a shift in the distribution of phenotypes and to the emergence of temporary - phenotypic - sexual dimorphism. The female sex leaves the zones of selection and discomfort, and retains the spectrum of past genotypes. The resulting difference between male and female gametes is partially preserved even after fertilization, since the information transmitted through the Y chromosome never passes from father to daughter. The fact that part of the genetic information remains in the male subsystem and does not enter the female subsystem is also evidenced by the existence of reciprocal effects - the fact that during hybridization it is not indifferent which breed the father is from and which the mother is from.
So, different cross-sections of the channel and the norm of reaction of male and female sexes in the moving environment inevitably lead, already in one generation, to the emergence of genotypic sexual dimorphism. In subsequent generations, in the moving environment, it can accumulate and grow.
Sexual dimorphism in phylogeny
If we move to the phylogenetic time scale, then in dioecious forms, after changing the stabilizing environment to the driving one, for many generations the trait changes only in the male sex. For females, the old meaning of the trait is retained. The evolutionary trajectory of the trait bifurcates into male and female branches, and a “divergence” of the trait occurs in the two sexes—the appearance and growth of genotypic sexual dimorphism. This - divergent a phase in which the rate of evolution of a trait is greater in the male sex.
After some time, when the possibilities of the reaction norm and other female defense mechanisms are exhausted, the trait begins to change in him too. Genotypic sexual dimorphism, having reached its optimum, remains constant. This - stationary the phase when the rates of evolution of a trait in males and females are equal. When in the male sex a trait reaches a new evolutionarily stable value, in the female sex it continues to change. This - convergent the phase of evolution of a trait when its speed is greater in the female sex. Genotypic sexual dimorphism gradually decreases and, with the merging of characters in the two sexes, disappears. Therefore, the phases of the evolution of the trait in males and females are shifted in time: in males they begin and end earlier than in females.
Since the evolution of a trait always begins with the expansion of its genotypic variance and ends with its narrowing, then in the divergent phase the variance is wider in the male sex, and in the convergent phase - in the female. This means that by sexual dimorphism and gender dispersion one can judge the direction and phase of evolution of a trait.
Sexual dimorphism by traits
All signs can be divided into three groups according to the degree of difference between the sexes.
Signs that are the same in both sexes
The first group includes those characteristics in which there is no difference between the male and female sexes. These include qualitative characteristics that manifest themselves at the species level - the general plan and fundamental structure of the body for both sexes, the number of organs, and many others. Sexual dimorphism for these characteristics is normally absent. But it is observed in the field of pathology. Girls more often show atavistic anomalies (resets or arrests of development), and boys - futuristic ones (search for new paths). For example, among 4,000 newborn children with three kidneys, there were 2.5 times more girls than boys, and among 2,000 children with one kidney, there were approximately 2 times more boys. Let us recall that our distant ancestors had a pair of excretory organs - metanephridia - in each segment of the body. Consequently, three kidneys in girls is a return to the ancestral type (atavistic direction), and one kidney in boys is a futuristic tendency. The same picture is observed among children with an excess number of ribs, vertebrae, teeth, etc., that is, organs that have undergone a decrease in number in the process of evolution - there are more girls among them. Among newborns with their shortage, there are more boys. A similar picture is observed in the distribution of congenital heart defects and great vessels.
Traits that are unique to one gender
The second group includes characteristics found only in one sex. These are primary and secondary sexual characteristics: genitals, mammary glands, beard in humans, mane in lions, as well as many economic characteristics (production of milk, eggs, caviar, etc.). Sexual dimorphism for them is genotypic in nature, since these characteristics are absent in the phenotype of one sex, but hereditary information about these characteristics is recorded in the genotype of both sexes. Therefore, if they evolve, then there must be genotypic sexual dimorphism in them. It is found in the form of reciprocal effects.
Traits present in both sexes
The third group of characters is in the middle between the first (there is no sexual dimorphism) and the second group (sexual dimorphism is absolute). It includes signs that occur in both males and females, but are distributed in the population with different frequencies and degrees of severity. These are quantitative characteristics: height, weight, size and proportions, many morphophysiological and ethological-psychological characteristics. Sexual dimorphism in them is manifested as the ratio of their average values. It is true for the entire population, but may have the opposite meaning for a single pair of individuals. It is this sexual dimorphism that serves as a “compass” for the evolution of the trait.
Sexual dimorphism and evolution of characters
Sexual dimorphism is closely related to the evolution of a character: it should be absent or minimal for stable characters and maximum, most clearly expressed, for phylogenetically young (evolving) characters. Like the other two main characteristics of a dioecious population - dispersion and sex ratio, sexual dimorphism is not considered as a constant inherent this species, as was previously thought, but as a variable and adjustable quantity, closely related to environmental conditions and determining, in turn, the evolutionary plasticity of the trait. Because in changeable extreme environment If greater plasticity is required than in a stable (optimal) environment, then sexual dimorphism in a stable environment should decrease, and in a changeable environment it should increase.
Sexual dimorphism and reproductive structure of the population
Sexual dimorphism should be associated with the reproductive structure of the population: in strict monogamists it should be minimal, since monogamists use sexual specialization only at the organismal level; in polygamous species, which more fully use the advantages of differentiation, it should increase with increasing degree of polygamy.
Sexual dimorphism in reciprocal hybrids (“Paternal effect”)
Based on characteristics inherent only to one sex (primary and secondary sexual characteristics, as well as many economically valuable characteristics: production of eggs, milk, caviar), sexual dimorphism has an absolute, organismal character. Since these characteristics are absent in the phenotype of one sex, genotypic sexual dimorphism can be judged from them by reciprocal effects. If according to the “old” (stable) traits the genetic contribution of the father to the offspring is on average slightly less than the contribution of the mother (due to the maternal effect due to cytoplasmic inheritance, homogametic constitution and uterine development in mammals), then according to the “new” characters, according to evolutionary theory gender, there must be some dominance of paternal characteristics over maternal ones.
The paternal effect has been established for alcoholism in humans, for the brooding instinct, precocity, egg production and live weight in chickens, for growth dynamics, the number of vertebrae and the length of the small intestine in pigs, for milk yield and milk fat production in cattle. The presence of a paternal effect in milk yield and egg production means nothing more than a higher genotypic “milk yield” in bulls and “egg production” in roosters than in cows and chickens of the same breeds.
Sexual dimorphism in anthropology
According to Geodakyan, the concept of gender theory, about the isolation of new and old information over many generations, allows us to explain a number of incomprehensible phenomena in anthropology. Thus, in the Turkmen population, using the generalized portrait method, a clear difference by gender was discovered - female portraits fit into one type, and male portraits into two types. A similar phenomenon was observed by R. M. Yusupov in the craniology of the Bashkirs - female skulls were close to the Finno-Ugric type (geographically, these are the northwestern neighbors of modern Bashkirs), and male skulls were close to the Altai, Kazakh and others (eastern and southeastern neighbors ). In the Udmurt population, dermatoglyphics in women corresponded to the Northwestern type, and in men - to the East Siberian type. L.G. Kavgazova noted the similarity of the dermatoglyphics of Bulgarians with Turks, while Bulgarians were closer to Lithuanians. Female forms of phenotypes show the original ethnic group, while male forms- number of sources and direction of gene flows. The facts given above show the Finno-Ugric origin of the Udmurt and Bashkir ethnic groups, differing in culture and language. The four-modal distribution of skulls of the male part of the population, according to V. Geodakyan, is explained by the influence of three different invasions from the south and east. The direction of gene flows in these populations is from southeast to northwest, and for the Bulgarian population - from south to north. He also states that the island population (Japanese), in full accordance with the theory, is monomodal for both sexes.
Evolutionary theory of sex - rules
Ecological rule of sex differentiation
In optimal, stable environmental conditions, when there is no need for high evolutionary plasticity, the main characteristics decrease and have minimum value, - that is, the birth rate (at the same time the mortality rate) of boys is falling, their diversity and the difference between male and female sexes is decreasing. All this reduces the evolutionary plasticity of the population. In extreme conditions of a changing environment, when rapid adaptation requires high evolutionary plasticity, reverse processes occur: at the same time, the birth rate and mortality rate (that is, the “turnover rate”) of the male sex, its diversity, and sexual dimorphism become clearer. All this increases the evolutionary plasticity of the population.
Rule of criterion for the evolution of a trait
A trait evolves if there is sexual dimorphism in it, and is stable when there is no sexual dimorphism.
Main article: Phylogenetic rule of sexual dimorphism
“If genotypic population sexual dimorphism exists for any trait, then this trait evolves from a female to a male form.”
The rule is part of the Evolutionary Theory of Sex. From the point of view of the systematic approach applied by V. A. Geodakyan in 1965 to the problem of sex, sexual dimorphism is considered as a consequence of the asynchronous evolution of the sexes. Consequently, sexual dimorphism occurs only according to evolving characters. This is an evolutionary “distance” between the sexes, which appears with the beginning of the evolution of a trait and disappears with its end. Accordingly, sexual dimorphism can be a consequence of any type of selection, and not just sexual, as Darwin believed.
Phylogenetic rule of sex dispersion
If the variance of a trait in males is greater than in females, evolution is in divergent phase, if the variances of the sexes are equal - the phase of evolution stationary, if the dispersion is greater in females, then the phase convergent. Dispersion is the diversity of traits in males and females.
IN dioecious population, each gender has its own dispersion value - and . Other parameters are the number of individuals, sex ratio and sexual dimorphism. The total contribution of variance, sex ratio and sexual dimorphism determines the degree differentiation floors
Inheritance of parental characteristics
It was found that female offspring inherit parental traits more additively (intermediate, arithmetic mean inheritance) than male offspring. Differences between male and female mice were observed for the relative weights of the adrenal glands, thymus, gonads, and pituitary glands, as well as genes responsible for locomotor activity.
Phenotypic variance
The greater phenotypic dispersion of the male sex is one of the main provisions of the evolutionary theory of sex. Since phenotypic dispersion reflects genotypic dispersion, it can be expected that in males it should be wider due to mutations and non-additive inheritance of traits. The degree of connection between the genotype and the phenotype (reaction norm) also determines the amount of phenotypic variance.
Sex dispersion in phylogeny
It can also be said that the female form of the trait is more typical for the initial, juvenile stage of ontogenesis, and the male form is more characteristic for the definitive, mature stage. In other words, female forms of traits should, as a rule, weaken with age, and male forms should increase.
Darwin drew attention to the closer connection of the female sex with the initial phase of ontogenesis. He wrote: “In the entire animal kingdom, if the male and female sexes differ from each other in appearance, with rare exceptions it is the male and not the female that is modified, because the latter usually remains similar to young animals of its own species and to other members of the whole groups." Anthropologists have also noted the proximity female type with children's (more graceful bones, weakly defined brow ridges, less body hair, etc.).
Hair distribution on the body of women and men
A striking example is the connection between the degree of development of horns in different species of deer and antelope with the age of their appearance in males and females: the more pronounced hornedness is in a species as a whole, the more early age horns appear: first in males and later in females. The ontogenetic rule of sexual dimorphism was confirmed on 16 anthropometric characters: relative length of the legs, forearm, 4th and 2nd fingers, cephalic index, dental arch circumference, epicanthus, nasal hump, body hair, facial and head hair, concentration of erythrocytes in the blood , pulse rate, gallbladder emptying rate, brain asymmetry, reaction time, phenylthiourea bitter taste sensation and sense of smell.
Phylogenetic rule of reciprocal effects
“In reciprocal hybrids, according to the divergent characteristics of the parents, the paternal form (breed) should dominate, and according to the converging characteristics, the maternal form.”
Main article: Teratological rule of sexual dimorphism
“Developmental anomalies that have an “atavistic” nature should appear more often in the female sex, and those that have a “futuristic” nature (search) - in the male sex.” According to species (and higher ranks of community) characteristics (multicellularity, warm-bloodedness, number of organs, plan and fundamental structure of the body, etc.), sexual dimorphism is normally absent. It is observed only in the field of pathology and is expressed in different frequencies of occurrence of certain congenital malformations in males and females. The classification of congenital anomalies into “atavistic” (returns or arrests of development) and “futuristic” (search for new ways) allows, in some cases, to trace in sexual dimorphism those predicted by the evolutionary theory of sex general trends. For example, among about 2,000 newborn children born with one kidney, there were approximately twice as many boys, while among 4,000 children with three kidneys, there were approximately 2.5 times as many girls. In lancelets and sea worms (distant predecessors of mammals), each body segment has a pair of specialized excretory organs - metanephridia. Therefore, the appearance of three buds can, in a certain sense, be considered an “atavistic” trend, and one bud as a “futuristic” trend. The same picture is observed among newborn children with an excess number of ribs, vertebrae, teeth and other organs that have undergone a reduction in number and oligomerization in the process of evolution - there are more girls among them. Among newborns with their shortage, on the contrary, there are more boys.
Congenital hip dislocation
The rule was also tested on the material of congenital heart defects and great vessels (32 thousand cases). It has been shown that female developmental anomalies are in the nature of preservation of embryonic features of the structure of the heart, characteristic of the last stages of intrauterine development, or features characteristic of species standing at lower steps of the evolutionary ladder (recent past) (open oval foramen in the interatrial septum and Botall's duct) . Elements of “male” defects (stenoses, coarctation, transposition of the great vessels) have a “futuristic” nature (search).
Matching Rule
Main article: Correspondence rule of V. A. Geodakyan
If there is a system of interconnected phenomena in which time-oriented past and future forms can be distinguished, then there is a correspondence (closer connection) between all past forms, on the one hand, and between future ones, on the other.
The correspondence rule was formulated by V. A. Geodakyan in 1983 and illustrated by the example of past and future forms of signs in different phenomena. In 1866, the Haeckel-Müller biogenetic law was discovered, establishing a connection between the phenomena of phylogenesis and ontogenesis (ontogenesis is a brief repetition of phylogeny).
If, for simplicity, we talk not about the organism as a whole, but only about one of its characteristics, then the phenomenon of phylogenesis is the dynamics (appearance and change) of a trait on an evolutionary time scale, in the history of the species. The phenomenon of ontogenesis is the dynamics of a trait in the life history of an individual. Consequently, the Haeckel-Müller law connects the ontogenetic and phylogenetic dynamics of a trait.
In 1965, V. A. Geodakyan discovered a pattern connecting the phenomenon of population sexual dimorphism with phylogenesis. “If there is genotypic population sexual dimorphism for any trait, then this trait evolves from the female to the male form.”
In 1983, he theoretically predicted a pattern connecting the phenomenon of sexual dimorphism with ontogenesis. “If there is population sexual dimorphism for any trait, then during ontogenesis this trait changes, as a rule, from the female to the male form.”
Let us introduce the concepts of two forms of a trait associated with the time vector in each of the three phenomena (phylogeny, ontogenesis and sexual dimorphism). In the phylogenesis of a trait we will distinguish between its “atavistic” and “futuristic” forms, in the ontogenesis of a trait - its “juvenile” (young) and “definitive” (adult) forms, and in population sexual dimorphism - its “female” and “male” forms . Then the generalized pattern connecting the phenomena of phylogenesis, ontogenesis and sexual dimorphism can be formulated as a “correspondence rule” between atavistic, juvenile And female forms of signs, on the one hand, and between futuristic, definitive And male forms - on the other.
The “rule of correspondence” can be extended to other phenomena that are systematically related to phylogenesis and ontogenesis (evolution), in which past and future forms can be distinguished. For example, the phenomenon of mutation (phylogenetic process of genes occurrence), the phenomenon of dominance (ontogenetic process of gene manifestation), the phenomenon of heterosis and reciprocal effects. The connection between the phenomena of phylogenesis, ontogenesis, mutation, dominance and sexual dimorphism is indicated by the following known facts like: more high degree spontaneous mutations in males; more additive inheritance of parental characteristics by female descendants, and therefore more dominant inheritance by male descendants; well-known autosomal genes that manifest themselves in the female genome as recessive traits, and in the male genome as dominant and increasing in ontogenesis, for example, the horned-polled gene in sheep, or the gene that causes baldness in humans, as well as the dominance of the paternal form over the maternal in evolving ( new) characteristics (“paternal effect”).
Predictions
Phylogenetic and ontogenetic rules of sexual dimorphism, connecting the phenomenon of sexual dimorphism with the dynamics of a trait in phylogeny and ontogenesis, make it possible, knowing one phenomenon, to predict two others. It is known that in distant phylogenetic predecessors of humans, the eyes were located laterally, their visual fields did not overlap, and each eye was connected only to the opposite hemisphere of the brain - contralaterally. During the process of evolution, in some vertebrates, including the ancestors of humans, in connection with the acquisition of stereoscopic vision, the eyes moved forward. This led to an overlap of the left and right visual fields and to the emergence of new ipsilateral connections: left eye - left hemisphere, right eye - right. Thus, it became possible to have in one place visual information from the left and right eyes - to compare them and measure depth. Therefore, ipsilateral connections are phylogenetically younger than contralateral ones. Based on the phylogenetic rule, it is possible to predict evolutionarily more advanced ipsi connections in males compared to females, that is, sexual dimorphism in the proportion of ipsi/contra fibers in the optic nerve. Based on the ontogenetic rule, it is possible to predict an increase in the proportion of ipsi fibers in ontogenesis. And since visual-spatial abilities and three-dimensional imagination are closely related to stereoscopy and ipsi connections, it becomes clear why they are better developed in men. This explains the observed differences between men and women in understanding geometric tasks, orienting and determining directions, reading drawings and geographical maps (see, for example, “Male and female strategy for orienteering” // Behavioral Neuroscience).
Applying the same rules to the human olfactory receptor leads to the conclusion that, in phylogenesis, human sense of smell, unlike vision, deteriorates. Since, as people age, olfactory fibers have been shown to atrophy and their number in the olfactory nerve steadily decreases, it can be predicted that their number should be greater in women than in men.
- In most vertebrate species, the evolution of which was accompanied by an increase in size, males should often be larger than females.
- In many species of insects and arachnids, which, on the contrary, became smaller, males should be smaller than females.
- For all selection traits, in cultivated plants and animals, males must be superior to females.
- In reciprocal hybrids, according to the diverging characteristics of the parents, the paternal form (breed) should dominate, and according to the converging characteristics, the maternal form.
- Signs of the recent phylogenetic past should be more common in females, and signs of a near possible future - in males.
- It is known that the relative sizes of the corpus callosum increase during human ontogenesis. This means that it should be greater in men and increase in phylogeny.
Criticism and attitude towards other theories
There is no criticism of gender theory in general in the literature. Criticism of certain aspects is sometimes encountered. For example, in the book by L. A. Gavrilov and N. S. Gavrilova, sex differences in life expectancy are analyzed. Regarding the greater variability of traits in males being responsible for their increased mortality, the authors note that “this hypothesis does not reveal a specific molecular genetic mechanism leading to longer life expectancy in females.” And they also write there that this drawback “can, in principle, be eliminated during further development and specification of this hypothesis.” They believe that the theory’s prediction about the predominance of men among long-livers does not agree with the facts, since, firstly, “as life expectancy increases, the differences in this area between men and women also grow” and secondly, “in recent years, in developed countries, an accelerated decline in the mortality rate of older women compared to men.” They also believe that “the long life expectancy of females is not at all a general biological pattern.” It should be noted that the conclusion about the longer life expectancy of females in most of the studied species was made long before the appearance of the theory of sex in a number of works.
Since Charles Darwin himself believed that the male sex changes earlier, the main position of V. Geodakyan’s concept, that the evolution of the sexes occurs asynchronously, does not contradict Darwin’s theory of evolution. IN Lately in the West it is even widely used new term“male-driven evolution”. V. Geodakyan’s theory complements and expands the theory of sexual selection of Charles Darwin, noting that sexual dimorphism can arise as a result of any (and not just sexual) selection.
V. Geodakyan's theory analyzes the process of sexual differentiation, and therefore does not contradict numerous theories trying to explain the emergence and maintenance of sexual reproduction, since they focus on the process of crossing.
Among the theories of dioecy, the theory of sex is more general than, for example, the theory of Parker (1972), which explains sexual differentiation at the gamete level and only in aquatic animals.
see also
- Gender differences
- The principle of coupled subsystems
- Paternal effect
Notes
- Geodakyan V. A. (1986) Sexual dimorphism. Biol. magazine Armenia. 39 No. 10, p. 823-834.
- Geodakyan V. A., Sherman A. L. (1970) Experimental surgery and anesthesiology. 32 No. 2, p. 18-23.
What might be responsible for the individual differences between males and females? Obviously, to answer this question it is necessary to go beyond psychology and turn to theories and hypotheses existing in ethology and biology.
The question of why gender exists at all has arisen for a long time. The simplest answer - for reproduction - cannot be considered satisfactory. In the living world, in addition to dioecious reproduction, there is also asexual (vegetative) and hermaphrodite reproduction, and dioecious reproduction has no obvious advantages over them. On the contrary, the combinatorial potential (combination of genes) in hermaphrodites is twice as high, and the number of offspring (reproduction efficiency) is higher in asexuals. However, all progressive forms reproduce sexually (3, 5).
To clarify the role of dioecious reproduction, in 1965, the domestic biologist V.A. Geodakyan (under the obvious influence of cybernetics and systems theory) created the so-called evolutionary theory of sex. In which the author argued that the differentiation of the sexes is associated with specialization in two main aspects of the evolutionary process - preservation and change of genetic information as a form of information contact with the environment beneficial for the population. Obviously, only male (or only female) individuals are not enough to ensure the continuity and development of the species. They must coexist.
Having based his theory on the principle of conjugate subsystems, Geodakyan noted that adaptive systems evolving in a driving environment significantly increase their overall stability subject to differentiation into two conjugate subsystems, with conservative and operational specialization, which belong to female and male individuals, respectively. How does this happen?
Initially, the female body has a wider reaction rate than the male body. So, if a man in conflict behavior, for example, usually behaves explosively, then it is hardly possible to make him tolerant and peaceful. And a woman can combine several strategies in her behavior, using them flexibly depending on the situation. Thanks to this, the adaptive abilities of females are much higher and their learning ability is better. (Research on educational psychology notes that the initial level of abilities is usually higher in boys, but in the process of learning they quickly reach a plateau, while girls, starting from lower indicators, pick up the pace and overtake boys.) If we we'll come to classroom and look at the performance of children, it turns out that girls (like boys) are equally divided into excellent students, poor students and mediocre students. However, if we pose the question differently: who is the most notorious loser and hooligan, who is the most talented student? - it turns out that these groups are filled, as a rule, with boys. That is, the male subsample has more specialized behavior, which generally hinders adaptation at the individual level. All extremes are more clearly represented in men, but women are more trainable.
Let us assume that the species’ environment remains virtually unchanged (such an environment is called stabilizing). In this environment, natural selection leads to a simple increase in the number of individuals, without changing their genotype. For this purpose, there is no need for the presence of a large number of males in the population, the main thing is that there are a sufficiently large number of females. And indeed, in stable conditions, slightly fewer boys are born (there is even a sign that many boys are born for war).
But if the environment abruptly changes its conditions (becomes driving), then the tasks of selection in adaptation change somewhat; it leads not only to an increase in the number of individuals, but also to a change in the genotype. In conditions of disasters (ecological, social, historical), elimination and exclusion from reproduction mainly affect the male sex, and modification - the female. Thanks to the differentiation of the sexes, two main changes appeared compared to asexual reproduction - a wider cross-section of the information channel of interaction in the male individual and a wider reaction norm in the female individual. Thus, a male individual can fertilize a larger number of females, and a female individual can provide a spectrum of phenotypes from one genotype.
After the disappearance of the catastrophic factor and the end of selection, the proportion of male individuals decreases, and their genotypic dispersion narrows (those who did not survive leave no genetic traces). So, women provide permanent phylogenetic memory of the species, and men provide temporary, ontogenetic memory (3).
To illustrate this idea, Geodakyan cites the following poetic example. When there was a general cooling on the planet, women, as highly adapted creatures, increased their fat layer. And men, due to their poor adaptability, turned out to be incapable of this and for the most part simply died out. But the remaining one invented fire to warm the entire community, and from that moment on, it was his genotype that began to be fixed. So, men carry out the search, and women – improvement. This is the mechanism of evolutionary biological (and psychological) progress.
It is obvious that, having a narrow reaction norm, men are more biologically (and psychologically) vulnerable. Therefore, their life expectancy is lower. Newborn boys are more likely to die than girls. However, the majority of centenarians are still men.
Of course, not all anatomical, physiological and behavioral characteristics develop and change, but only some. The presence of differences in characteristics between males and females is called sexual dimorphism, i.e. the existence of two forms (and in psychology they have already begun to use the expression sexual dippsychism). In modern people, for example, there is sexual dimorphism in terms of height, weight, hair growth, but there is no dimorphism in terms of the number of fingers or ears, or eye color.
In a stabilizing environment, there is no sexual dimorphism (there is no need to adapt, and male and female individuals have the same evolutionarily advantageous trait value). And in the moving environment, genotypic sexual dimorphism appears already in one generation, increasing in subsequent generations. By the variability of a trait, one can judge the phase of the evolutionary process based on the trait. Thus, if the variance in the male subsample is higher than in the female subsample, this indicates the beginning of the evolutionary process, and the selection phase is called divergent. Then comes the parallel phase, in which the variances in both groups are approximately equal. Finally, the convergent phase, in which variation in women increases compared to men, indicates that the evolutionary process is close to completion.
Geodakyan formulated the phylogenetic rule of sexual dimorphism: if there is population sexual dimorphism for any trait, then this trait evolves from the female to the male form. That is, the population is masculinized, and the trait values that exist in the male subsample are evolutionarily advantageous. This applies to all species that have dioecious reproduction. So, for example, if in mammals the female is smaller in size than the male, this means that as the evolutionary process progresses, females will increase in size because this is beneficial for the species. In insects (for example, spiders), females, on the contrary, are much larger than males; this suggests that it is easier for a light creature to survive in its environment. Consequently, the females will become smaller.
This fact is also used in breeding: since selection traits are more advanced in fathers, sire selection is a key problem for developing new breeds, even if it concerns hidden traits, such as milk yield.
There is also an ontogenetic rule of sexual dimorphism: if there is population sexual dimorphism for any trait, then during ontogenesis this trait changes, as a rule, from the female to the male form. The rule of the paternal effect in selection is that according to the diverging traits of the parents (which are the subject of attention), the paternal form (breed) should dominate, and according to the converging traits (not essential for breeding the breed), the female form should dominate.
It is interesting that in ontogenesis, female forms of the trait appear earlier, and male forms later. Thus, young children of both sexes are more like girls, and in older people, again, regardless of gender, masculine traits begin to appear (a rough voice, growth of facial hair, etc.). Based on the characterological characteristics of a little girl, one can more reliably predict the personality structure and behavior of an adult woman than in boys. Therefore, we can talk not only about dimorphism, but also about dichronomorphism (i.e., a temporary discrepancy in the manifestation of female and male characteristics) (3, 6).
It is noteworthy that congenital anomalies of an “atavistic” nature more often appear in women, and “futuristic” ones - in men. Thus, among newborn girls there are more often those with tails. However, the longest tail, measuring 13 cm, still belonged to a boy. Sexual dimorphism is observed both in the area of the appearance of diseases (all new diseases, such as cancer, AIDS, first appeared in men), and in the structure of the brain (in men, the asymmetry of the hemispheres and operating systems are more pronounced - the cortex and the left hemisphere, and in women - conservative systems - subcortex and right hemisphere, which determines the predominance of analytical thinking in men, and intuitive, imaginative and sensory cognition in women). Due to less asymmetry, women are also more trainable. In addition, in the cultural and historical process, the flagship role of men is observed: each new profession was at first only male and only then became female, and the main scientific discoveries and cultural revolutions were also made by men.
© V.A. Geodakyan
EVOLUTIONARY THEORY OF SEX V.A. Geodakyan
Vigen Artavazdovich Geodakyan, doctor biological sciences, senior Researcher Institute of Evolutionary Morphology and Animal Ecology named after. A.N. Severtsov USSR Academy of Sciences. Theoretical biologist. Scientific interests include sex-related problems of evolution, genetics, ecology, brain asymmetry and psychology, as well as issues of information and systems organization.Unfortunately, for technical reasons, pictures are not shown - V.V.
NOT ONE natural phenomenon has aroused such interest or contained so many mysteries as gender. The problem of sex was dealt with by the greatest biologists: C. Darwin, A. Wallace, A. Weissman, R. Goldschmidt, R. Fischer, G. Meller. But mysteries remained, and modern authorities continued to talk about the crisis of evolutionary biology. "Sex is the main challenge to modern evolutionary theory... the queen of problems in evolutionary biology,"- says G. Bell - “The intuitions of Darwin and Mendel, which illuminated so many mysteries, could not cope with the central mystery of sexual reproduction.”. Why are there two genders? What does this give?
The main advantages of sexual reproduction are usually associated with ensuring genetic diversity, suppressing harmful mutations, and preventing inbreeding - inbreeding. However, all this is the result of fertilization, which also occurs in hermaphrodites, and not differentiation (separation) into two sexes. In addition, the combinatorial potential of hermaphroditic reproduction is two times higher than that of dioecious reproduction, and the quantitative efficiency of asexual methods is two times higher than that of sexual ones. It turns out that the dioecious method is the worst? Why then are all evolutionarily progressive forms of animals (mammals, birds, insects) and plants (dioecious) dioecious?
The author of these lines, back in the early 60s, expressed the idea that gender differentiation is an economical form of information contact with the environment, specialization in two main “aspects of evolution - conservative and operational. Since then, it has been possible to uncover a number of patterns and create a theory that explains many different facts from a unified perspective and predicts new ones.The essence of the theory will be presented in the article.
TWO SEXES - TWO STREAM OF INFORMATION
In principle, two solutions to this conflict are possible for the system: to be at some optimal “distance” from the environment or to split into two coupled subsystems - conservative and operational, the first one “moved away” from the environment in order to preserve the existing information, and the second one “brought closer” to the environment to get a new one. The second solution increases the overall stability of the system, therefore it is often found among evolving, adaptive, tracking systems (regardless of their specific nature) - biological, social, technical, etc. This is precisely the evolutionary logic of sex differentiation. Asexual forms “adhere” to the first solution, dioecious forms to the second.
If we distinguish two flows of information: generative (transfer of genetic information from generation to generation, from the past to the future) and ecological (information from the environment, from the present to the future), then it is easy to see that the two sexes participate in them differently. In the evolution of sex, at different stages and levels of organization, a number of mechanisms appeared that consistently ensured a closer connection of the female sex with the generative (conservative) flow, and the male sex with the ecological (operational) flow. Thus, the male sex, compared to the female sex, has a higher frequency of mutations, less additivity of inheritance of parental characteristics, a narrower reaction norm, higher aggressiveness and curiosity, more active search, risky behavior and other qualities that “bring closer to the environment.” All of them, purposefully placing the male sex on the periphery of distribution, provide him with preferential receipt of environmental information. Another group of features is the huge redundancy of male gametes, their small size and high mobility, greater activity and mobility of males, their tendency to polygamy and other ethological and psychological properties. Long periods of pregnancy, feeding and caring for offspring in females, actually increasing the effective concentration of males, turn the male sex into “surplus”, therefore, “cheap”, and the female into scarce and more valuable.
This leads to the fact that selection operates mainly due to the exclusion of male individuals; “redundancy” and “cheapness” allow it to work with large coefficients. As a result, the number of males in the population decreases, but their greater potential allows them to fertilize all females. A small number of males transmits as much information to their offspring as a large number of females; in other words, the channel of communication with offspring is wider for males than for females. This means that the genetic information transmitted through the female line is more representative, but through the male line it is selective, i.e., in the female line the past diversity of genotypes is more fully preserved, while in the male line the average genotype changes more strongly.
Let's move on to the population - an elementary evolving unit.
Any dioecious population is characterized by three main parameters: sex ratio (the ratio of the number of males to the number of females), sex dispersion (the ratio of the variance values of a trait, or its diversity, in males and females), sexual dimorphism (the ratio of the average values of a trait for males and females). floors). Attributing a conservative mission to the female sex, and an operational one to the male sex, the theory connects these population parameters with environmental conditions and the evolutionary plasticity of the species.
In a stable (optimal) environment, when there is no need to change anything, conservative tendencies are strong and evolutionary plasticity is minimal. In a driving (extreme) environment, when it is necessary to increase plasticity, operational tendencies intensify. In some species, say lower crustaceans, these transitions are carried out by switching from one type of reproduction to another (for example, in optimal conditions - parthenogenetic, in extreme conditions - dioecious). In most dioecious species, this regulation is smooth: under optimal conditions, the main characteristics decrease (the birth rate of males falls, their dispersion narrows, sexual dimorphism decreases), and under extreme conditions they increase (this is the ecological rule of sex differentiation).
Since environmental stress leads to their sharp growth, these population parameters can serve as an indicator of the state of the ecological niche. In this regard, it is significant that the birth rate of boys in Karakalpakstan has increased by 5% over the past decade. According to the ecological rule, the basic parameters should increase during any natural or social disasters (major earthquakes, wars, famine, relocations, etc.). Now about the elementary step of evolution.
TRANSFORMATION OF GENETIC INFORMATION IN ONE GENERATION
A genotype is a program that in different environments can be realized into one of a whole range of phenotypes (traits). Therefore, the genotype does not record a specific value of a trait, but a range of possible values. In ontogenesis, one phenotype is realized, the most suitable for a particular environment. Consequently, the genotype specifies a range of realizations, the environment “selects” a point within this range, the width of which is the reaction norm, characterizing the degree of participation of the environment in determining the trait
For some characteristics, for example, blood type or eye color, the reaction norm is narrow, so the environment does not actually influence them; for others - psychological, intellectual abilities - it is very wide, so many associate them only with the influence of the environment, i.e. upbringing; third characteristics, say height, mass, occupy an intermediate position.
Taking into account two differences between the sexes - in the reaction rate (which is wider in females) and in the cross-section of the communication channel (wider in males) - let us consider the transformation of genetic information in one generation, i.e. from zygotes to zygotes, in becoming a bilizing and driving environment . Let us assume that the initial distribution of genotypes in the population is the same for male and female zygotes, i.e., there is no sexual dimorphism for the trait in question. In order to obtain from the distribution of zygote genotypes the distribution of phenotypes (organisms before and after selection), from it, in turn, the distribution of egg and sperm genotypes, and, finally, the distribution of zygotes of the next generation, it is enough to trace the transformation of two extreme genotypes of zygotes into extreme phenotypes, extreme gametes and again into zygotes. The remaining genotypes are intermediate and will remain so in all distributions. The wider reaction norm of the female sex allows it, due to modification plasticity, to leave the selection zones, preserve and transmit to the offspring the entire spectrum of the original genotypes.
The narrow reaction norm of the male sex forces him to remain in the zones of elimination and undergo intense selection. Therefore, the male sex transmits to the next generation only a narrow part of the original spectrum of genotypes, which best corresponds to the environmental conditions at the moment. In a stabilizing environment this is the middle part of the spectrum, in a driving environment it is the edge of the distribution. This means that the genetic information transmitted by the female sex to the offspring is more representative, and that transmitted by the male sex is more selective. Intensive selection reduces the number of males, but since the formation of zygotes requires an equal number of male and female gametes, males have to fertilize more than one female. The wide cross-section of the male channel allows this. Consequently, in each generation of the population, eggs of a wide variety, carrying information about the past richness of genotypes, merge with sperm of a narrow variety, the genotypes of which contain information only about the ones most suitable for current environmental conditions. Thus, the next generation receives information about the past from the maternal side, and information about the present from the paternal side.
In a stabilizing environment, the average genotypes of male and female gametes are the same, only their variances differ, therefore the genotypic distribution of zygotes of the next generation coincides with the initial one. The only result of sex differentiation in this case comes down to the population paying for environmental information with the “cheaper” male sex. The picture is different in the driving environment, where changes affect not only variances, but also the average values of genotypes. Genotypic sexual dimorphism of gametes arises, which is nothing more than a recording (fixation) of environmental information in the distribution of male gametes. What is his future fate?
If paternal genetic information is transmitted stochastically to sons and daughters, at fertilization it will become completely mixed and sexual dimorphism will disappear. But if there are any mechanisms that prevent complete mixing, some of this information will pass from fathers only to sons and, therefore, some sexual dimorphism will be retained in zygotes. But such mechanisms exist. For example, only sons receive information from the genes of the Y chromosome; Genes are expressed differently in offspring, depending on whether they are inherited from the father or mother. Without such barriers, it is also difficult to explain the dominance of the paternal genotype in offspring from reciprocal crosses, known in animal husbandry, for example, the high milk yield of cows transmitted through a bull. All this allows us to believe that only gender differences in the reaction rate and the cross-section of the communication channel are sufficient for genotypic sexual dimorphism to arise in the driving environment already in one generation, which will accumulate and grow as generations change.
DIMORPHISM AND DICHRONISM IN PHYLOGENESIS
So, when the stabilizing environment becomes driving for a given trait, the evolution of the male trait begins. gender, but in the female it remains, that is, the divergence of the character occurs, from monomorphic it turns into dimorphic.
From several possible evolutionary scenarios, two obvious facts allow us to choose the only one: both sexes evolve; There are both mono- and dimorphic characters. This is only possible if the phases of the evolution of the trait in the sexes are shifted in time: in the male, the change in the trait begins and ends earlier than in the female. Moreover, according to the ecological rule, the minimum dispersion of a trait in a stabilizing environment expands with the beginning of evolution and narrows at its completion.
The evolutionary trajectory of the trait bifurcates into male and female branches, and sexual dimorphism appears and grows. This is the divergent phase in which the rate of evolution and dispersion of the trait is male. After many generations, the variance in the female sex begins to expand and the trait begins to change. Sexual dimorphism, having reached its optimum, remains constant. This is a parallel phase: the rates of evolution of the trait and its dispersion in both sexes are constant and equal. When the trait reaches a new, stable value in the male sex, the variance narrows and evolution stops, but still continues in the female sex. This is the convergent phase in which the rate of evolution and dispersion is greater in the female sex. Sexual dimorphism gradually decreases and, when the trait becomes the same in the sexes, disappears, and the variances level out and become minimal. This completes the dimorphic stage of evolution of the trait, which is again followed by the monomorphic, or stability stage.
Thus, the entire phylogenetic trajectory of the evolution of a trait consists of alternating monomorphic and dimorphic stages, and the theory considers the presence of dimorphism itself as a criterion for the evolution of the trait.
So, sexual dimorphism for any trait is closely related to its evolution: it appears with its beginning, persists while it continues, and disappears as soon as evolution ends. This means that sexual dimorphism is a consequence not only of sexual selection, as Darwin believed, but of any kind: natural, sexual, artificial. This is an indispensable stage, a mode of evolution of any trait in dioecious forms, associated with the formation of a “distance” between the sexes along the morphological and chronological axes. Sexual dimorphism and sexual dichronism are two dimensions of a common phenomenon - dichronomorphism.
The above can be formulated in the form of phylogenetic rules of sexual dimorphism and sex dispersion: if there is population sexual dimorphism for any trait, then the trait evolves from the female to the male form; if the dispersion of a trait is greater in the male sex - the phase is divergent, the dispersions are equal - parallel, the dispersion is greater in the female sex - the convergent phase. According to the first rule, one can determine the direction of evolution of a trait, and according to the second, its phase, or the path traveled. Using the rule of sexual dimorphism, a number of easily testable predictions can be made. Thus, based on the fact that the evolution of most vertebrate species was accompanied by an increase in size, it is possible to establish the direction of sexual dimorphism - in large forms, males are, as a rule, larger than females. Conversely, since many insects and arachnids have become smaller during evolution, in small forms the males should be smaller than the females.
The rule can be easily tested on farm animals and plants whose artificial evolution (selection) was directed by humans. Selection - economically valuable - traits should be more advanced in males. There are many such examples: in meat breeds of animals - pigs, sheep, cows, birds - males grow faster, gain weight and produce better quality meat; stallions are superior to mares in sports and working qualities; rams of fine wool breeds produce 1.5-2 times more wool than sheep; Male fur-bearing animals have better fur than females; male silkworms produce 20% more silk, etc.
Let us now move from the phylogenetic time scale to the ontogenetic one.
DIMORPHISM AND DICHRONISM IN ONTOGENESIS
If each of the phases of the phylogenetic scenario is projected onto ontogeny (according to the law of recapitulation, ontogenesis is a brief repetition of phylogeny), we can obtain the corresponding six (three phases in the evolutionary stage and three in the stable; pre-evolutionary, post-evolutionary and inter-evolutionary) different scenarios for the development of sexual dimorphism in the individual development. Dichronism will manifest itself in ontogenesis as an age-related delay in the development of a trait in the female sex, i.e., the dominance of the female form of a dimorphic trait at the beginning of ontogenesis and the male form at the end. This is an ontogenetic rule of sexual dimorphism: if there is population sexual dimorphism for any trait, during ontogenesis this trait changes, as a rule, from the female to the male form. In other words, the characteristics of the maternal breed should weaken with age, and those of the paternal breed should strengthen. Testing this rule against two dozen anthropometric characteristics completely confirms the prediction of the theory. A striking example is the development of antlers in different species of deer and antelope: the stronger the “hornedness” of a species, the earlier in ontogenesis antlers appear, first in males and then in females. The same pattern - age-related delay in development in females due to functional asymmetry of the brain - was revealed by S. Vitelzon. She examined the ability of 200 right-handed children to recognize objects by touch with their left and right hands and found that boys already at the age of 6 had a right-hemisphere specialization, and girls up to 13 years old were “symmetrical.”
The described patterns refer to dimorphic, evolving characters. But there are also monomorphic, stable ones, in which sexual dimorphism is normally absent. These are fundamental characteristics of the species and higher ranks of community, such as multicellularity, warm-bloodedness, a body plan common to both sexes, the number of organs, etc. According to the theory, if their dispersion is greater in the male sex, then the phase is pre-evolutionary, if in the female - post-evolutionary. In the last phase, the theory predicts the existence of "relics" of sexual dimorphism and gender dispersion in pathology. The "relic" of dispersion manifests itself as an increased frequency of congenital anomalies in the female sex, and the "relic" of sexual dimorphism - in their different directions. This is the teratological rule of sexual dimorphism: congenital anomalies of an atavistic nature should appear more often in females, and those of a futuristic nature (search) - in males. For example, among newborn children with an excess number of kidneys, ribs, vertebrae, teeth, etc. - all organs , who have undergone a reduction in number during evolution, there should be more girls, and with their shortage - boys. Medical statistics confirm this: among 2 thousand children born with one kidney, there are approximately 2.5 times more boys, and among 4 thousand. There are almost twice as many children with three kidneys as girls. This distribution is not accidental; it reflects the evolution of the excretory system. Consequently, three kidneys in girls is a return to the ancestral type of development, an atavistic direction; one kidney for boys is futuristic, a continuation of the reduction trend. The statistics for the anomalous number of edges are similar. Five to six times more girls than boys are born with dislocated hips, a congenital defect that makes children better at running and climbing trees than healthy ones.
The picture is similar in the distribution of congenital heart defects and great vessels. Of the 32 thousand verified diagnoses, all “female” defects were dominated by elements characteristic of the embryonic heart or human phylogenetic predecessors: an open foramen ovale in the interatrial septum, a non-closed botal duct (the vessel connecting the fetal pulmonary artery to the aorta), etc. “Male” the defects were more often new (search): they had no analogues either in phylogeny or in embryos - various kinds of stenosis (narrowing) and transposition of the great vessels.
The listed rules cover dimorphic characteristics inherent in both sexes. What about traits that are characteristic only of one sex, such as egg production and milk yield? Phenotypic sexual dimorphism for such traits is of an absolute, organismal nature, but hereditary information about them is recorded in the genotype of both sexes. Therefore, if they evolve, there must be genotypic sexual dimorphism in them, which can be found in reciprocal hybrids. Based on such characteristics (among other evolving ones), the theory predicts the direction of reciprocal effects. In reciprocal hybrids, according to the divergent characteristics of the parents, the paternal form (breed) should dominate, and according to the converging characteristics, the maternal form. This is the evolutionary rule of reciprocal effects. It provides an amazing opportunity to reveal greater genotypic advancement of the male sex, even based on purely female characteristics. This seemingly paradoxical prediction of the theory is fully confirmed: in the same breed, bulls are genotypically “more productive” than cows, and roosters are more “egg-laying” than hens, i.e., these traits are transmitted predominantly by males.
Problems of evolution mostly refer to "black boxes" without an input - direct experimentation is impossible in them. Evolutionary teaching drew the necessary information from three sources: paleontology, comparative anatomy and embryology. Each of them has significant limitations, since it covers only part of the characteristics. The formulated rules provide a new method for evolutionary research on absolutely all characteristics of dioecious forms. Therefore, the method is of particular value for studying human evolution, its characteristics such as temperament, intelligence, functional asymmetry of the brain, verbal, spatial-visual, creative abilities, humor and other psychological properties to which traditional methods are not applicable.
FUNCTIONAL ASYMMETRY OF THE BRAIN AND PSYCHOLOGICAL FEATURES
For a long time it was considered a human privilege, associated with speech, right-handedness, self-awareness, and it was believed that asymmetry was secondary - a consequence of these unique human characteristics. It has now been established that asymmetry is widespread in placental animals; most researchers also recognize the difference in its severity in men and women. J. Levy believes, for example, that the female brain is similar to the brain of a left-handed man, that is, less asymmetrical than that of a right-handed man.
From the perspective of gender theory, more asymmetrical brains in men (and the males of some vertebrates) mean that evolution is moving from symmetry to asymmetry. Sexual dimorphism in brain asymmetry offers hope for understanding and explaining differences in the abilities and inclinations of men and women.
It is known that our distant phylogenetic ancestors had lateral eyes (in human embryos at early stages of development they are located in the same way), the visual fields did not overlap, each eye was connected only to the opposite hemisphere (contralateral connections). In the process of evolution, the eyes moved to the front side, the visual fields overlapped, but for a stereoscopic picture to arise, visual information from both eyes had to be concentrated in one area of the brain.
Vision became stereoscopic only after additional ipsilateral fibers appeared, which connected the left eye to the left hemisphere, and the right to the right. This means that the ipsilateral connections are evolutionarily younger than the contralateral ones, and therefore in men they should be more advanced, i.e. there are more ipsilateral fibers in the optic nerve.
Since three-dimensional imagination and spatial-visual abilities are associated with stereoscopy (and the number of ipsi-fibers), they should be better developed in men than in women. Indeed, psychologists are well aware that men are far superior to women in understanding geometric problems, as well as in reading maps, orienteering, etc.
How did psychological sexual dimorphism arise, from the point of view of gender theory? There is no fundamental difference in the evolution of morphophysiological and psychological or behavioral traits. The wide norm of reaction of the female sex provides it with higher plasticity (adaptability) in ontogenesis than that of the male sex. This also applies to psychological signs. Selection in zones of discomfort in males and females goes in different directions: thanks to a wide reaction norm, the female sex can “get out” of these zones due to education, learning, conformity, i.e., in general, adaptability. For the male sex, this path is closed due to the narrow norm of reaction; only resourcefulness, quick wits, and ingenuity can ensure his survival in uncomfortable conditions. In other words, women adapt to the situation, men get out of it by finding a new solution, discomfort stimulates the search.
Therefore, men are more willing to take on new, challenging, and extraordinary tasks (often doing them in rough drafts), while women are better at solving familiar problems to perfection. Is this why they excel in jobs that require highly polished skills, such as assembly line work?
If mastery of speech, writing, or any craft is considered in an evolutionary aspect, we can distinguish the phase of search (finding new solutions), mastery and the phase of consolidation and improvement. A male advantage in the first phase and a female advantage in the second was revealed in special studies.
Innovation in any business is the mission of the male gender. Men were the first to master all professions, sports, even knitting, in which women's monopoly is now undeniable, was invented by men (Italy, 13th century). The role of the avant-garde belongs to men and exposure to certain diseases and social vices. It is the male sex that is more often susceptible to “new” diseases, or, as they are called, diseases of the century; civilization, urbanization - atherosclerosis, cancer, schizophrenia, AIDS, as well as social vices - alcoholism, smoking, drug addiction, gambling, crime, etc.
According to the theory, there should be two opposing types of mental illness, associated with the vanguard role of the male gender and the rearguard role of the female.
Pathology, which is accompanied by insufficient brain asymmetry, small size of the corpus callosum and large anterior commissures, should be two to four times more common in women, anomalies with the opposite characteristics - in men. Why?
If there are no differences between the sexes in a quantitative trait, then the distribution of its values in the population is often described by a Gaussian curve. The two extreme regions of such a distribution are the zones of pathology - “plus” and “minus” deviations from the norm, into each of which male and female individuals fall with equal probability. But if sexual dimorphism exists, then in each sex the trait is distributed according to -in their own way, two curves are formed, separated by the amount of sexual dimorphism. Since they remain within the general population distribution, one zone of pathology will be enriched in males, the other - in females. By the way, this also explains the “sexual specialization” characteristic of the population of almost all countries of the world in many other countries diseases.
The above examples show how the theory of gender “works” only in some human problems; in fact, it covers a much larger array of phenomena, including the social aspect.
Since the dimorphic state of a trait indicates that it is on the “evolutionary march,” the differences in the most recent evolutionary acquisitions of man—abstract thinking, creative abilities, spatial imagination, and humor—should be maximum; they should predominate in men. Indeed, outstanding scientists, composers, artists, writers, directors are mostly men, and there are many women among the performers.
The problem of gender affects very important areas of human interest: demography and medicine, psychology and pedagogy, the study of alcoholism, drug addiction and crime; through genetics it is connected with economics. A correct social concept of gender is needed to solve problems of fertility and mortality, family and education, and professional guidance. Such a concept must be built on a natural biological basis, because without understanding the biological, evolutionary roles of the male and female sexes, it is impossible to correctly determine their social roles.
Here are presented only a few general biological conclusions of the theory of sex; various previously incomprehensible phenomena and facts are explained from a unified position; prognostic possibilities are mentioned. So, let's summarize. The evolutionary theory of sex allows:
- 1) predict the behavior of the main characteristics of a dioecious population in stable (optimal) and driving (extreme) environments;
- 2) differentiate evolving and stable traits;
- 3) determine the direction of evolution of any trait;
- 4) establish the phase (path traveled) of the evolution of the trait;
- 5) determine the average rate of evolution of the trait: V= dimorphism/dichronism
- 6) predict six different variants of the ontogenetic dynamics of sexual dimorphism corresponding to each phase of phylogeny;
- 7) predict the direction of dominance of the paternal or maternal breed trait in reciprocal hybrids;
- 8) predict and reveal “relics” of gender dispersion and sexual dimorphism in the field of congenital pathologies;
- 9) establish a connection between age and sex epidemiology.
So, the specialization of the female sex in preserving genetic information, and the male sex in changing it, is achieved by the heterochronic evolution of the sexes. Consequently, sex is not so much a method of reproduction, as is commonly believed, but a method of asynchronous evolution.
Since the work presented here is the fruit of theoretical reflections and generalizations, it is impossible not to say a few words about the role of theoretical research in biology. Natural science, according to the famous physicist and Nobel Prize winner R. Millikan, moves on two legs - theory and experiment. But this is how things are - in physics, in biology the cult of facts reigns, it still lives by observations and experiments, theoretical biology as such, an analogue of theoretical physics does not exist. Of course, this is due to the complexity of living systems, hence the skepticism of biologists who are accustomed to following the traditional path - from facts and experiments to generalizing conclusions and theory. But can the science of living things still remain purely empirical in the “age of biology,” which, as many contemporaries recognize, is replacing the “age of physics”? I think it’s time for biology to stand on both legs.
Literature
Bell G., The Masterprice of Nature. The Evolution and Genetics of Sexuality, London, 1982.
. Geodakyan V. A. // Probl. transmission of information 1965. T. 1. No. 1. P. 105-112.
. For more details see; Geodakyan V. A. Evolutionary logic of sex differentiation // Nature. 1983. No. 1. P. 70-80.
. Geodakyan V. A. // Dokl. Academy of Sciences of the USSR. 1983. T. 269. No. 12. P. 477-482.
. Vitelson S.F..// Science. 1976. V. 193. M 4251. R. 425-427.
. Geodakyan V. A., Sherman A. L. // Journal. total biology. 1971. T. 32. No. 4. P. 417-424.
. Geodakyan V. A. // System research: methodological problems. Yearbook. 1986. M., 1987. pp. 355-376.
. Geodakyan V. A. The theory of gender differentiation in human problems // Man in the system of sciences. M., 1989. pp. 171-189.
With environmental conditions and evolutionary plasticity of the population. In optimal, stable environmental conditions, these characteristics are minimal, that is, the birth rate (at the same time the mortality rate) of boys decreases, their diversity and the difference between the male and female sexes are reduced. All this reduces the evolutionary plasticity of the population. In extreme conditions, when rapid adaptation requires high evolutionary plasticity, reverse processes occur: the birth rate and mortality rate (that is, the “turnover rate”) of the male sex and its diversity simultaneously increase, and sexual dimorphism becomes clearer.
Since 1965, more than 150 works have been published on the theory of sex and related issues - life expectancy, differentiation of the brain and hands, sex chromosomes, regulatory mechanisms in plants and animals, heart defects and other diseases, and even culture; reports have been made on many domestic publications. And international congresses conferences and symposia. Two conferences were devoted exclusively to theory (St. Petersburg, Russia, 1990, 1992). The theory has been included in textbooks and teaching programs of a number of universities and institutes. The theory has been repeatedly written about in the pages of periodicals. Three interviews were shown on television in A. Gordon's program.
Analysis of the gender problem
The concept of gender includes two fundamental phenomena: sexual process(fusion of genetic information of two individuals) and sexual differentiation(dividing this information into two parts). Depending on the presence or absence of these phenomena, the many existing methods of reproduction can be divided into three main forms: asexual, hermaphroditic and dioecious. The sexual process and sexual differentiation are different phenomena and, in essence, diametrically opposed. The sexual process creates a variety of genotypes, and this is the advantage of sexual methods over asexual methods, recognized by many scientists. Sexual differentiation, by imposing a ban on same-sex combinations (mm, lj), on the contrary, reduces it by half. That is, during the transition from hermaphroditic to dioecious reproduction, at least half of the diversity is lost.
Then, it is not clear what the division into two sexes gives if it halves the main achievement of sexual reproduction? Why are all species of animals (mammals, birds, insects) and plants (dioecious) progressive in evolutionary terms dioecious, while there are clear advantages of quantitative efficiency and simplicity in asexual forms, and diversity of offspring in hermaphroditic ones?
To solve the riddle of dioeciousness, it is necessary to explain what differentiation gives, and for this it is necessary to understand the advantages of dioeciousness over hermaphroditism. This means that dioeciousness, which they try in vain to understand as the best method of reproduction, is not such at all. It's effective way of evolution.
Conservative-operative specialization of sexes
The division into two sexes is a specialization in preserving and changing information in a population. One sex should be informationally more closely connected with the environment, and be more sensitive to its changes. Increased male mortality from all environmental factors allows us to consider it operational, ecological subsystem of the population. The female gender is more stable conservative subsystem and preserves the existing distribution of genotypes in the population.
In the evolution of sex, at different stages and levels of organization, a number of mechanisms appeared that consistently ensured a closer connection of the female sex with the generative (conservative) flow, and the male sex with the ecological (operational) flow. Thus, the male sex, compared to the female sex, has a higher frequency of mutations, less additivity of inheritance of parental characteristics, a narrower reaction norm, higher aggressiveness and curiosity, more active search, risky behavior and other qualities that “bring closer to the environment.” All of them, purposefully placing the male sex on the periphery of distribution, provide him with preferential receipt of environmental information.
Another group of features is the huge redundancy of male gametes, their small size and high mobility, greater activity and mobility of males, their tendency towards polygamy and other ethological and psychological properties. Long periods of pregnancy, feeding and caring for offspring in females, actually increasing the effective concentration of males, turn the male sex into “surplus”, therefore, “cheap”, and the female into scarce and more valuable.
As a result of the conservative-operative specialization of the sexes, their asynchronous evolution occurs: new characteristics first appear in the operational subsystem (male sex) and only then enter the conservative (female sex).
Wider female reaction norm
Obtaining environmental information from the environment
Firstly, a change in environmental factors can eliminate the most sensitive to a given factor part of the population as a result of natural selection. Secondly, a change in environmental factors, creating uncomfortable conditions, can completely or partially exclude another part of the population from reproduction, due to sexual selection. Thirdly, the changed environment modifies the surviving part of the population, creating morpho-physiological, behavioral and other non-heritable adaptations due to reaction norms. For example, in the cold, animals' tails shorten, their fur becomes thicker, and their subcutaneous fat layer thickens. Man uses caves, clothes, fire.
The first two processes (elimination and discrimination) remove some genotypes from the reproduction pool. The third process (modification), on the contrary, allows some genotypes to be preserved under the guise of a modified phenotype and enter the gene pool of the offspring. That is, someone has to be broken, killed, removed, and someone has to be bent, “educated”, remade.
To obtain ecological information from the environment, the male sex must have greater phenotypic variance, which may be a consequence of wide genotypic variance. It may also be a consequence of a broader hereditary norm of reaction in females, which allows them to leave zones of elimination and discomfort. The wider genotypic variance in males may result from higher mutation rates in males. and also that female offspring inherit. More additive inheritance of parental traits by females can reduce their variance compared to males.
Mechanisms for regulating population parameters
Two mechanisms control population parameters in animals - stress and sex hormones. Plants receive environmental information from their environment through pollen counts. The specific nature of the environmental factor due to which the body experiences discomfort does not, apparently, have any significance for the triggering of these mechanisms, that is, it makes no difference whether the discomfort is caused by frost, drought, hunger or enemies. In all unfavorable conditions, with a certain intensity of discomfort, it develops stressful state, that is, such “generalized” environmental information is, as it were, “one-dimensional” - only “good” or “bad”.
Sex ratio
Increased male mortality
Hamilton (1948) provides a review of differential mortality between the sexes for 70 species, including: various shapes life, such as nematodes, molluscs, crustaceans, insects, arachnids, birds, reptiles, fish, mammals. According to these data, in 62 species (89%) the average lifespan of males is shorter than that of females; for most of the rest there is no difference, and only in some cases the life expectancy of males is longer than that of females.
The evolutionary theory of sex considers increased male mortality as a beneficial form of information contact with the environment for the population, carried out through the elimination of some individuals in the population by a harmful environmental factor. For example, all “new” diseases, diseases of the “century” or “civilization” (heart attack, atherosclerosis, hypertension, etc.), as a rule, are diseases of the male gender.
“Turnability” of males in extreme environmental conditions
In changing, extreme environmental conditions, male mortality increases and the tertiary sex ratio of the population decreases. The more changeable the environment, the fewer males remain in the population, and at the same time, the more of them are required for adaptation. It is possible to compensate for a decrease in the tertiary sex ratio only by increasing the secondary one. In other words, under extreme environmental conditions, both the mortality and birth rates of males will simultaneously increase, that is, their “turnover” will increase.
Regulation of population sex ratio
Organismal mechanisms for regulating sex ratio
Negative feedback is realized in plants through the amount of pollen, and in animals through the intensity of sexual activity, aging, affinity and death of gametes. At the same time, a small amount of pollen, intense sexual activity of males, fresh sperm and old eggs should lead to an increase in the birth rate of males.
Population mechanisms of sex ratio regulation
To implement the population mechanism, it is necessary that the probability of having an offspring of a given sex differs among different individuals and is determined by their genotype. In this case, there should be an inverse relationship between the reproductive rank of a given individual and the sex of its offspring: the higher the reproductive rank, the more offspring of the opposite sex there should be. In this case, regulation can be carried out at the population level, with greater or lesser participation in the reproduction of individuals that produce an excess of males or females in their offspring.
“Cross section” of the channel for transmitting information to offspring
Father and mother pass on approximately the same amount of genetic information to each offspring, but the number of offspring to which a male can pass on genetic information is incomparably greater than the number to which a female can pass on information. Each male, in principle, can transmit information to the entire offspring of the population, while females are deprived of this opportunity. That is, the capacity—the “cross section”—of the communication channel between the male and his offspring is significantly greater than the cross section of the female’s communication channel.
Ontogenetic and phylogenetic plasticity
A wide reaction norm makes the female sex more changeable and plastic in ontogenesis. It allows females to leave zones of elimination and discomfort, gather in a comfort zone and reduce phenotypic variance and mortality.
The male's narrower reaction norm does not allow him to reduce phenotypic variance. Males remain in zones of elimination and discomfort and die or do not leave offspring. This allows the population to “pay” for new information, primarily through the sacrifice of male individuals.
The high ontogenetic plasticity of the female sex provides it with high stability in phylogenesis. Over the course of generations, the female sex more fully preserves the existing distribution of genotypes in the population. The genotypic distribution of males varies much more. Consequently, in phylogenetic terms, the male sex is more changeable and plastic, and in ontogenetic terms, on the contrary, the female sex is more plastic and changeable. This, at first glance paradoxical, distribution of roles in phylogeny and ontogenesis actually consistently and consistently implements the idea of specialization of the sexes according to the conservative and operational tasks of evolution.
Sexual dimorphism
Sexual dimorphism in one generation
Stable environmental conditions
In a stable environment, all transformations of genetic information affect gender variances, but do not affect the average values of traits. Therefore, there is no sexual dimorphism. There is only a difference in variance, which disappears when moving to the next generation. However, it is necessary that genotypic sexual dimorphism in reaction norms exists in advance (in a stable phase), and genetic information about a broad reaction norm should be transmitted only through the female line, and about a narrow reaction rate only through the male line.
Changing Environment
In the driving environment, the phenotypic distribution of males before selection roughly follows the original genotypic distribution. A broad reaction norm in the female sex leads to a shift in the distribution of phenotypes and to the emergence of temporary, phenotypic sexual dimorphism. The female sex leaves the zones of selection and discomfort, and retains the spectrum of past genotypes. The male sex remains in dangerous zones and is subject to selection. After the action of selection, the proportion of male individuals decreases and their genotypic dispersion narrows. In the driving environment, transformations affect both sex variances and average trait values: the reaction norm creates temporary, phenotypic sexual dimorphism, genotypic selection. The male sex receives new environmental information. An increase in male mortality increases the male birth rate due to negative feedback.
The resulting difference between male and female gametes is partially preserved even after fertilization, since the information transmitted through the Y chromosome never passes from father to daughter. The fact that part of the genetic information remains in the male subsystem and does not enter the female subsystem is also evidenced by the existence of reciprocal effects, the fact that during hybridization it is not indifferent what breed the father is from, what breed the mother is from.
So, different cross-sections of the channel and the reaction rate of male and female sexes in the moving environment inevitably lead in one generation to the emergence of genotypic sexual dimorphism. In subsequent generations, in the moving environment, it can accumulate and grow.
Sexual dimorphism in phylogeny
If we move to the phylogenetic time scale, then in dioecious forms, after changing the stabilizing environment to the driving one, for many generations the trait changes only in the male sex. In females, the old meaning of the trait is retained. The evolutionary trajectory of the trait bifurcates into male and female branches, and a “divergence” of the trait occurs in the two sexes—the appearance and growth of genotypic sexual dimorphism. This- divergent a phase in which the rate of evolution of a trait is greater in the male sex.
After some time, when the possibilities of the reaction norm and other mechanisms of protection of the female sex are exhausted, the trait begins to change in him. Genotypic sexual dimorphism, having reached its optimum, remains constant. This- stationary the phase when the rates of evolution of a trait in males and females are equal. When in the male sex a trait reaches a new evolutionarily stable value, in the female sex it continues to change. This- convergent the phase of evolution of a trait when its speed is greater in the female sex. Genotypic sexual dimorphism gradually decreases and, with the merging of characters in the two sexes, disappears. Therefore, the phases of the evolution of the trait in males and females are shifted in time: in males they begin and end earlier than in females. Since the evolution of a trait always begins with the expansion of its genotypic variance and ends with its narrowing, then in the divergent phase the variance is wider in the male sex, and in the convergent phase in the female. This means that by sexual dimorphism and gender dispersion one can judge the direction and phase of evolution of a trait.
Sexual dimorphism by traits
All signs can be divided into three groups according to the degree of difference between the sexes.
Signs are the same in both sexes
The first group includes those characteristics in which there is no difference between the male and female sexes. These include qualitative characteristics that manifest themselves at the species level - the general plan and fundamental structure of the body for both sexes, the number of organs, and many others. Sexual dimorphism for these characteristics is normally absent. But it is observed in the field of pathology. Girls more often show atavistic anomalies (resets or arrests of development), and boys - futuristic ones (search for new paths). For example, among 4,000 newborn children with three kidneys, there were 2.5 times more girls than boys, and among 2,000 children with one kidney, there were approximately 2 times more boys. Let us recall that our distant ancestors had a pair of excretory organs - metanephridia - in each segment of the body. Consequently, three kidneys in girls is a return to the ancestral type (atavistic direction), and one kidney in boys is a futuristic tendency. The same picture is observed among children with an excess number of ribs, vertebrae, teeth, etc., that is, organs that have undergone a decrease in number in the process of evolution - there are more girls among them. Among newborns with their shortage, there are more boys. A similar picture is observed in the distribution of congenital heart defects and great vessels.
Traits that are unique to one gender
The second group includes characteristics found only in one sex. These are primary and secondary sexual characteristics: genitals, mammary glands, beard in humans, mane in lions, as well as many economic characteristics (production of milk, eggs, caviar, etc.). Sexual dimorphism for them is genotypic in nature, since these characteristics are absent in the phenotype of one sex, but hereditary information about these characteristics is recorded in the genotype of both sexes. Therefore, if they evolve, then there must be genotypic sexual dimorphism in them. It is found in the form of reciprocal effects.
Traits present in both sexes
The third group of characters is in the middle between the first (there is no sexual dimorphism) and the second group (sexual dimorphism is absolute). It includes signs that occur in both males and females, but are distributed in the population with different frequencies and degrees of severity. These are quantitative characteristics: height, weight, size and proportions, many morphophysiological and ethological-psychological characteristics. Sexual dimorphism in them is manifested as the ratio of their average values. It is true for the entire population, but may have the opposite meaning for a single pair of individuals. It is this sexual dimorphism that serves as a “compass” for the evolution of the trait.
Sexual dimorphism and evolution of characters
Sexual dimorphism is closely related to the evolution of a character: it should be absent or minimal for stable characters and maximum, most clearly expressed for phylogenetically young (evolving) characters. Like the other two main characteristics of a dioecious population—dispersion and sex ratio—sexual dimorphism is considered not as a constant characteristic of a given species, as previously thought, but as a variable and adjustable quantity, closely related to environmental conditions and determining, in turn, evolutionary plasticity sign. Since in a changeable, extreme environment greater plasticity is required than in a stable (optimal) one, sexual dimorphism in a stable environment should decrease, and in a changeable environment it should increase.
Sexual dimorphism and reproductive structure of the population
Sexual dimorphism should be related to the reproductive structure of the population: in strict monogamists it should be minimal, since monogamists use sexual specialization only at the organismal level. In polygamous species, which more fully take advantage of differentiation, it should increase with increasing degree of polygamy.
Sexual dimorphism in reciprocal hybrids (“Paternal effect”)
Based on characteristics inherent only to one sex (primary and secondary sexual characteristics, as well as many economically valuable characteristics - production of eggs, milk, caviar), sexual dimorphism has an absolute, organismal character. Since these characteristics are absent in the phenotype of one sex, genotypic sexual dimorphism can be judged from them by reciprocal effects. If, according to the “old” (stable) characteristics, the genetic contribution of the father to the offspring is on average slightly less than the contribution of the mother due to the maternal effect due to cytoplasmic inheritance, homogametic constitution and uterine development in mammals, then according to the “new” characteristics, according to the evolutionary theory of sex, there must be some dominance of paternal characteristics over maternal ones.
The paternal effect has been established for alcoholism in humans, for the brooding instinct, precocity, egg production and live weight in chickens, for growth dynamics, the number of vertebrae and the length of the small intestine in pigs, for milk yield and milk fat production in cattle. The presence of a paternal effect in milk yield and egg production means nothing more than a higher genotypic “milk yield” in bulls and “egg production” in roosters than in cows and chickens of the same breeds.
Sexual dimorphism in anthropology
The ideas of gender theory about the separation of new and old information over many generations make it possible to explain a number of incomprehensible phenomena in anthropology. Thus, in the Turkmen population, using the generalized portrait method, a clear difference by gender was discovered - female portraits fit into one type, and male portraits into two types. A similar phenomenon was observed by R. M. Yusupov in the craniology of the Bashkirs - female skulls were close to the Finno-Ugric type (geographically, these are the northwestern neighbors of modern Bashkirs), and male skulls were close to the Altai, Kazakh and others (eastern and southeastern neighbors ). In the Udmurt population, dermatoglyphics in women corresponded to the Northwestern type, and in men, to the East Siberian type. L.G. Kavgazova noted the similarity of the dermatoglyphics of Bulgarians with Turks, while Bulgarians were closer to Lithuanians. Female forms of phenotypes show the original ethnic group, while male forms show the number of sources and direction of gene flows. The facts given above show the Finno-Ugric origin of the Udmurt and Bashkir ethnic groups, differing in culture and language. The four-modal distribution of skulls of the male part of the population can be explained by the influence of three different invasions from the south and east. The direction of gene flows in these populations is from southeast to northwest, and for the Bulgarian population - from south to north. It is interesting to note that the island population (Japanese), in full accordance with the theory, turns out to be monomodal for both sexes.
Evolutionary theory of sex - rules
Ecological rule of sex differentiation
In optimal, stable environmental conditions, when there is no need for high evolutionary plasticity, the main characteristics decrease and have minimal significance, that is, the birth rate (at the same time the mortality rate) of boys decreases, their diversity and the difference between the male and female sexes are reduced. All this reduces the evolutionary plasticity of the population. In extreme conditions, in a changing environment, when rapid adaptation requires high evolutionary plasticity, the opposite processes occur: the birth rate and mortality rate (that is, the “turnover rate”) of the male sex, its diversity, and sexual dimorphism become clearer at the same time. All this increases the evolutionary plasticity of the population.
Rule of criterion for the evolution of a trait
A trait evolves if there is sexual dimorphism in it and is stable when there is no sexual dimorphism.
Ontogenetic rule of sexual dimorphism
“If there is population sexual dimorphism for any trait, then during ontogenesis this trait changes, as a rule, from the female to the male form.”
Phylogenetic rule of sexual dimorphism
If there is genotypic population sexual dimorphism for any trait, then this trait evolves from the female to the male form. Moreover, if the dispersion of a trait in males is greater than in females, evolution is in divergent phase, if the variances of the sexes are equal, the phase of evolution stationary, if the dispersion is greater in females, then the phase convergent.
Phylogenetic rule of reciprocal effects
“In reciprocal hybrids, according to the divergent characteristics of the parents, the paternal form (breed) should dominate, and according to the converging characteristics, the maternal form.”
Teratological rule of sexual dimorphism
“Developmental anomalies that have an “atavistic” nature should appear more often in the female sex, and those that have a “futuristic” nature (search) should appear more often in the male sex.”
Matching Rule
If there is a system of interconnected phenomena in which time-oriented past and future forms can be distinguished, then there is a correspondence (closer connection) between all past forms, on the one hand, and between future ones, on the other.
Phylogenetic and ontogenetic rules of sexual dimorphism, connecting the phenomenon of sexual dimorphism with the dynamics of a trait in phylogeny and ontogenesis, make it possible, knowing one phenomenon, to predict two others. It is known that in distant phylogenetic predecessors of humans, the eyes were located laterally, their visual fields did not overlap, and each eye was connected only to the opposite hemisphere of the brain - contralaterally. During the process of evolution, in some vertebrates, including the ancestors of humans, due to the acquisition of stereoscopic vision, the eyes moved forward. This led to an overlap of the left and right visual fields and to the emergence of new ipsilateral connections: the left eye - the left hemisphere, the right eye - the right. Thus, it became possible to have visual information from the left and right eyes in one place, for comparing them and measuring depth. Therefore, ipsilateral connections are phylogenetically younger than contralateral ones. Based on the phylogenetic rule, it is possible to predict evolutionarily more advanced ipsi connections in males compared to females, that is, sexual dimorphism in the proportion of ipsi/contra fibers in the optic nerve. Based on the ontogenetic rule, it is possible to predict an increase in the proportion of ipsilateral fibers in ontogenesis. And since visual-spatial abilities and three-dimensional imagination are closely related to stereoscopy and ipsi connections, it becomes clear why they are better developed in men. This explains the observed differences between men and women in the understanding of geometry and descriptive geometry - subjects that require three-dimensional vision.
Applying the same rules to the human olfactory receptor leads to the conclusion that, in phylogenesis, human sense of smell, unlike vision, deteriorates. Since, as people age, olfactory fibers have been shown to atrophy and their number in the olfactory nerve steadily decreases, it can be predicted that their number should be greater in women than in men.
Literature
- Geodakyan V. A. (1986) Sexual dimorphism. Biol. magazine Armenia. 39 No. 10, p. 823-834.
- Geodakyan V. A., Sherman A. L. (1970) Experimental surgery and anesthesiology. 32 No. 2, p. 18-23.
- Geodakyan V. A., Sherman A. L. (1971) The relationship of congenital developmental anomalies with gender. Zhypn. total biology. 32 No. 4, p. 417-424.