At the core synthetic theory of evolution (STE), or evolutionary synthesis, lies all the same Darwinism. However, it is supplemented with information from other biological sciences, primarily genetics, as well as ecology, molecular biology, systematics, etc.

Many features and patterns of the evolutionary process described by Darwin could not be fully explained by him due to the insufficient development of sciences at that time. This served as the basis for a well-founded criticism of evolutionary theory. For example, Jenkin noticed that any change that occurs in one individual will gradually dissolve as a result of interbreeding and, therefore, cannot be fixed as a result of the struggle for existence (the so-called "Jenkin's nightmare"). Darwin and his followers could not give counterarguments, since they had little idea of ​​the discrete nature of heredity, although discovered by Mendel in the 60s of the XIX century, but recognized in science only at the beginning of the XX century.

Discoveries in the field of genetics, molecular biology, population studies and the coming to understand how and why a population is a unit of evolution have led to the fact that evolutionary theory has ceased to be something like a hypothesis, but has been explained and largely proven. The mechanisms of evolution were more deeply revealed, the reasons for changing the gene pool of a population were described, the role of DNA as the material basis of heredity and variability was discovered, and much more.

The population-genetic approach occupies an important place in the synthetic theory of evolution. Population genetics studies how the driving forces of evolution affect the change in allele frequencies in populations, the spatial structure of populations, and explains speciation.

In the 1930s, the works of Fisher, Haldane, and Dobzhansky showed the relationship between the degree of genetic variability of a population and the rate of its evolution.

In 1942, Huxley proposed the concept of "evolutionary synthesis", and in 1949 Simpson used the term "synthetic theory of evolution".

Evolution in STE is considered as a gradual process of changing the gene pool of populations (the allele frequencies of different genes change, new alleles and genes appear, others disappear).

According to the synthetic theory of evolution the elementary unit of evolution is the population.

Under elementary evolutionary factors in STE and population genetics, they understand processes that change the set and frequency of alleles. Allocate a row major evolutionary factors(slightly different in different sources):

Natural selection in the synthetic theory of evolution is considered as the most important factor in the evolutionary process. As a result of the action of natural selection, the genotypes most adapted to a given habitat are reproduced to a greater extent. Natural selection can be directed both against certain alleles and certain genotypes (combinations of alleles and genes).

Struggle for existence. Darwin considered it the main factor in evolution, and natural selection was already a consequence of the struggle for existence.

mutation process leads to the emergence of new genetic material (new alleles of genes or even new genes). Although mutations are rare and most often harmful, they are in many ways the material for the action of natural selection.

gene flow is a change in the frequencies of alleles in a population as a result of the migration of individuals. In addition, gene flow leads to the exchange of genes between different populations, which reduces the likelihood of their divergence in the process of speciation.

Gene drift implies random changes in allele frequencies and is associated with sampling error, which is how it differs from gene flow. Genetic drift in the "founder effect" is the emergence of a new population from a small number of migrating individuals of another population. These individuals do not carry the entire gene pool of the original population, but only a part of the alleles. In the future, with reproduction and an increase in the number, the gene pool of the new population will differ from the original. Another type of genetic drift is the "bottleneck effect", when the population decreases sharply as a result of adverse conditions.

Insulation- the emergence of barriers between populations that prevent the interbreeding of individuals and the exchange of genes. As a result, each population can go its own evolutionary path.

The synthetic theory of evolution shows how heterozygotes (carrying usually deleterious recessive mutations) serve as a potential source of the evolutionary process. Recessive alleles are almost never completely eliminated from the population, and with a small number remain in heterozygotes.

In STE, importance is given to recombination of genetic material. Often it is considered as a secondary evolutionary factor that arises on the basis of the above listed primary evolutionary factors that create variability in individual genes, and gene recombination can already be considered as a secondary process.

Recombination produces a wide variety of genotypes in a population even with a small number of mutations. That is, with an insignificant level of diversity in alleles, a significant level of diversity in genotypes is observed (since the genotype consists of a huge number of genes).

Anyway mutational and recombination variability provide material for natural selection.

As a result of natural selection, populations and species adapt to the environment, speciation occurs (at the level of microevolution), the emergence of larger taxa (at the level of macroevolution).

It is assumed that the difficulties faced by the classical theory of evolution (see Section 5.5.2), in particular, in explaining the phenomenon of heredity, were overcome by synthesizing the evolutionary theory of Ch. Darwin and G. Mendel's genetics.

The synthetic theory of evolution (STE) is a modern evolutionary theory, which is a synthesis of various disciplines, primarily genetics and Darwinism, as well as paleontology, taxonomy, molecular biology, etc.

The synthetic theory in its current form was formed as a result of rethinking a number of provisions of classical Darwinism from the standpoint of genetics at the beginning of the 20th century.

After the rediscovery of the laws of G. Mendel (in 1901), the evidence of the discrete nature of heredity, and, especially, after the creation of theoretical population genetics by the works of R. Fisher, D.B.S. Haldane, Jr. and S. Wright, the teachings of Charles Darwin acquired a solid genetic foundation.

Article by S.S. Chetverikov "On some moments of the evolutionary process from the point of view of modern genetics" became the core of the future and the basis for further synthesis of Darwinism and genetics. This article shows the compatibility of the principles of genetics with the theory of natural selection and laid the foundations of evolutionary genetics.

In the works of J. Haldane, N.V. Timofeev-Resovsky and F.G. Dobzhansky’s ideas expressed by S.S. Chetverikov, spread to the West, where almost simultaneously R. Fischer expressed his views on the evolution of dominance.

The impetus for the development of STE was given by the hypothesis of the recessiveness of new genes. The hypothesis assumed that in each reproducing group of organisms during the maturation of gametes, as a result of errors in DNA replication, mutations constantly arise - new gene variants.

The influence of genes on the structure and functions of the body is such that each gene is involved in determining several traits. On the other hand, each trait depends on many genes. Geneticists call this phenomenon the genetic polymerization of traits.

The English geneticist R. Fisher in 1930 expressed the idea that polymerization reflects the interaction of genes, and therefore the external manifestation of each gene depends on its genetic environment. Therefore, recombination, generating more and more new gene combinations, eventually creates such a gene environment for a given mutation that allows the mutation to manifest itself in the phenotype of the carrier individual.

So the mutation falls under the influence of natural selection, which destroys combinations of genes that make it difficult for organisms to live and reproduce in a given environment, and preserves neutral and advantageous combinations. Moreover, first of all, such gene combinations are selected that contribute to a favorable and at the same time stable phenotypic expression of initially subtle mutations, due to which these mutant genes gradually become dominant.

In this way, the essence of the synthetic theory is the predominant reproduction of certain genotypes and the transfer of their characteristics to descendants. In the question of the source of genetic diversity, the synthetic theory recognizes the main role for recombination genes.

It is believed that the evolutionary act took place when selection retained a gene combination that was not typical for the previous history of the species.

An important prerequisite for the emergence of a new theory of evolution was the book of an English geneticist, mathematician and biochemist

J.B.S. Haldane Jr. "The causes of evolution"(1932). Haldane, creating the genetics of individual development, immediately included a new science in solving the problems of macroevolution.

Evolutionary innovations often arise on the basis of neoteny (preservation of juvenile traits in an adult organism). Neoteny J. Haldane explained the origin of man ("naked ape"), the evolution of other large taxa. In 1933 N.K. Koltsov, teacher S.S. Chetverikov, showed that neoteny in the animal kingdom is widespread and plays an important role in progressive evolution. It leads to morphological simplification, but the richness of the genotype is preserved.

In almost all historical and scientific models, 1937 was called the year of the emergence of STE. It was in this year that the book of the Russian-American geneticist and naturalist F.G. Dobzhansky. Dual Specialization F.G. Dobzhansky allowed him to be the first to throw a solid bridge from the camp of experimental biologists to the camp of naturalists.

For the first time, the most important concept of "isolation mechanisms of evolution" was formulated - reproductive barriers that separate the gene pool of one species from the gene pools of other species. F. G. Dobzhansky also introduced the “S. Wright effect” into naturalistic material, believing that microgeographic races arise under the influence of random changes in gene frequencies in small isolates, i.e. in an adaptive-neutral way.

In the English-language literature, among the creators of STE, the names of F.G. Dobzhansky, J. Huxley, E. Mayr, B. Rensch, J. Stebbins. This is of course not a complete list. Of the Russian scientists, at least I.I. Schmalhausen, N.V. Timofeev-Resovsky, G.F. Gause, N.P. Dubinina, A.L. Takhtajyan; from British scientists - J.B.S. Haldane, Jr., D. Lack, C. Waddington, G. de Beer; from German scientists - E. Baur, V. Zimmermann, V. Ludwig, G. Heberer and others.

As a result, in 1930-1940. a synthetic theory of evolution was created, which not only became the core of population genetics, but also made it possible to formulate a unified system of all modern biological knowledge.

In contrast to the classical evolutionary concept of Ch. Darwin, who considers a species as a unit of evolution, STE states that the elementary evolutionary structure is population.

It was believed that it was the population that possessed those properties of a self-organizing integral system that were necessary for hereditary changes.

A stable change in the genotype of a population is considered as an elementary phenomenon of the evolutionary process. The unit of heredity is a gene - a section of a DNA molecule responsible for the development of certain characteristics of an organism.

The main mechanism of the evolutionary process is the selection of organisms with mutations that are beneficial for adaptation to the environment.

Hereditary changes occur under the influence of a number of evolutionary factors:

• mutational process - mutational changes that supply material for evolution;
• population waves - fluctuations in the size of the population around a certain average level;
• isolation - isolation of a population to consolidate a new trait;
• natural selection is the leading factor in evolution - the survival of the fittest individuals and the birth of healthy offspring by them.

Mutations - this is a change in the hereditary properties of organisms within a population that occurs naturally or artificially and supplies the basic material for evolution. As already mentioned, mutagens are the temperature regime, the action of toxic substances, radiation, dietary habits, etc. .

After the discovery of the DNA double helix (1953), the mutation began to be interpreted in the spirit of Morgan's chromosome theory: they saw a change in the DNA text - in the structure of the nucleic acid within the locus - or in the structure of the chromosomes. Mutations began to be divided into gene (point), chromosomal and genomic. It seemed that any hereditary change was reduced to these three types of mutations. In connection with this limitation, it became possible to develop a genetic-population model of evolution in STE.

Along with the postulate that mutations are the only source of evolution, the STE has firmly established the idea of ​​a one-to-one correspondence between a mutation (gene) and a trait, that the emergence of a new stable phenotype is an automatic consequence of the manifestation of a mutation. From these positions, evolution appears as the result of sorting and accumulation by natural selection of a series of mutations.

Modern molecular biology classifies viruses as one of the most dangerous mutagens.

Mutations appear randomly, most of them are either dangerous or harmful. Harmful mutations often cause the death of an organism, and, as a rule, at fairly early stages of ontogeny; harmful mutations that do not lead to death are eliminated in the course of natural selection.

Favorable mutations are extremely rare, but they are what give an organism an evolutionary advantage. Random favorable mutations gradually accumulate in the population, are fixed in a number of generations and contribute to the evolution of the species.

Popular waves, or population wave, which are sometimes called "waves of life", determine the fluctuations in the population size around a certain average value. Studies have shown that medium-sized populations are most favorable for the emergence of new properties and the emergence of new species.

Insulation- Another factor in the evolutionary process, necessary to ensure that the population could not interbreed with other groups of organisms and exchange genetic information with them.

Expediency in wildlife is a consequence natural selection, which acts as a driving force and a leading factor in evolution. Selection acts at all stages of the development of a living organism, all properties without exception are subjected to it. In the classical theory of evolution, natural selection was defined as the process of survival of the fittest organisms.

Modern evolutionary biology focuses on the other side of this phenomenon. Natural selection is now understood as the elimination from reproduction of those individuals that are less adapted to environmental conditions.

The listed factors of evolution operate both at the microevolutionary (evolutionary changes in a population over a short period of time) and at the macroevolutionary level (a set of evolutionary changes over a long period of time, leading to the emergence of new supraspecific forms of organization of living things).

An important component of STE are the concepts of micro- and macroevolution.

Under microevolution understand the totality of evolutionary processes occurring in populations, leading to changes in the gene pool of these populations and the formation of new species.

It is believed that microevolution proceeds on the basis of mutational variability under the control of natural selection. Mutations are the only source of qualitatively new traits, and natural selection is the only creative factor in microevolution.

The nature of microevolutionary processes is influenced by fluctuations in the number of populations (“waves of life”), the exchange of genetic information between them, their isolation and gene drift. Microevolution leads either to a change in the entire gene pool of a biological species as a whole, or to isolation from the parent species as new forms.

Since macroevolution understand evolutionary transformations leading to the formation of taxa of a higher rank than the species (genera, orders, classes).

It is believed that macroevolution does not have specific mechanisms and is carried out only through the processes of microevolution, being their integrated expression. Accumulating, microevolutionary processes are expressed externally in macroevolutionary phenomena, i.e. macroevolution is a generalized picture of evolutionary change. Therefore, at the level of macroevolution, general trends, directions and patterns of evolution of living nature are found that cannot be observed at the level of microevolution. (For evolution not according to Charles Darwin, see Chapter 16.)

The main provisions of the synthetic theory of evolution

The synthetic theory of evolution - modern Darwinism - arose in the early 40s of the XX century. It is a doctrine of the evolution of the organic world, developed on the basis of data from modern genetics, ecology and classical Darwinism. The term "synthetic" comes from the title of the book by the famous English evolutionist J. Huxley "Evolution: a modern synthesis" (1942). Many scientists contributed to the development of the synthetic theory of evolution.

The main provisions of the synthetic theory of evolution can be summarized as follows:

The material for evolution is hereditary changes - mutations (as a rule, genes) and their combinations.

The main driving factor of evolution is natural selection, which arises on the basis of the struggle for existence.

The smallest unit of evolution is the population.

Evolution is in most cases divergent in nature, i.e. one taxon can become the ancestor of several daughter taxa.

Evolution is gradual and long lasting. Speciation as a stage of the evolutionary process is a successive change of one temporary population by a succession of subsequent temporary populations.

A species consists of many subordinate, morphologically, physiologically, ecologically, biochemically and genetically distinct, but reproductively non-isolated units - subspecies and populations.

The species exists as a holistic and closed formation. The integrity of the species is maintained by migrations of individuals from one population to another, in which there is an exchange of alleles ("gene flow"),

Macroevolution at a higher level than the species (genus, family, order, class, etc.) goes through microevolution. According to the synthetic theory of evolution, there are no patterns of macroevolution that are different from microevolution. In other words, the evolution of groups of species of living organisms is characterized by the same prerequisites and driving forces as for microevolution.

Any real (not composite) taxon has a monophyletic origin.

Evolution has an undirected character, that is, it does not go in the direction of any final goal.

The synthetic theory of evolution revealed the underlying mechanisms of the evolutionary process, accumulated many new facts and evidence of the evolution of living organisms, and combined data from many biological sciences. Nevertheless, the synthetic theory of evolution (or neo-Darwinism) is in line with the ideas and trends that were laid by Charles Darwin.

132. Current state of evolutionary science. Elementary factors of evolution. Driving factor of evolution. The role of mutation processes, population waves, isolation, gene drift and various types of natural selection in populations .

The current state of evolutionary teaching

Important achievements of modern evolutionary theory are related to the fact that the mechanisms of heredity and variability of organisms are now known, the internal organization and heterogeneity of a biological species have been established, and its complex population structure has been studied. The theory of natural selection has been further developed, otherwise the mechanisms of the evolutionary process are presented, a number of general rules for the historical development of groups of organisms have been established.

Elementary Factors of Evolution

There are four main elementary factors of evolution: mutation process, population waves, isolation, natural selection.

The mutation process is the process of occurrence in populations of a wide variety of mutations: gene, chromosomal and genomic. The mutation process is the most important elementary evolutionary factor, since it supplies the elementary evolutionary material - mutations. It is mutations that provide the emergence of new variants of a trait; it is mutations that underlie all forms of variability.

Population waves - Periodic or aperiodic fluctuations in the number of individuals in a population are characteristic of all living organisms without exception. The reasons for such fluctuations can be various abiotic and biotic environmental factors. The action of population waves, or waves of life, involves the indiscriminate, random destruction of individuals, due to which a rare genotype (allele) before the population fluctuation can become common and be picked up by natural selection. If in the future the population is restored due to these individuals, then this will lead to a random change in the frequencies of genes in the gene pool of this population. Population waves are the supplier of evolutionary material.

Isolation - in the process of evolution comes down to a violation of free interbreeding, which leads to an increase and consolidation of differences between populations and individual parts of the entire population of the species. Without such a fixation of evolutionary differences, no form formation is possible.

Natural selection is the differential survival and reproduction of individuals that differ from each other in genetically determined traits.

Driving form of natural selection. With this form of selection, mutations with one average value of the trait are eliminated, which are replaced by mutations with a different average value of the trait. In other words, this form of natural selection favors a change in the average value of a trait under changed environmental conditions. A classic example of this form is the so-called industrial melanism.

stabilizing selection. This form of natural selection is observed if the environmental conditions remain fairly constant for a long time, which helps to maintain the average value, rejecting mutational deviations from the previously formed norm.

Tearing (disruptive) selection. This form of natural selection favors more than one phenotype and is directed against the middle forms. This leads, as it were, to a rupture of the population according to this trait into several phenotypic groups, which can lead to polymorphism.

Sexual selection is natural selection regarding the traits of individuals of the same sex. Usually sexual selection results from the struggle between males (in rare cases - between females) for the opportunity to enter into reproduction. Sexual selection is not an independent factor in evolution, but only a special case of intraspecific natural selection.

Individual selection is reduced to the differentiated reproduction of individual individuals that have advantages in the struggle for existence within the population. Based on the competition of individuals within a population.

Group selection gives preferential reproduction of individuals of any group. In group selection, traits are fixed in evolution that are favorable for the group, but not always favorable for individuals. In group selection, groups of individuals compete with each other in creating and maintaining the integrity of supraorganismal systems.

Artificial selection is carried out by man in order to create new breeds or varieties that meet his needs.

Population waves are periodic fluctuations in the size of a population. For example: the number of hares is not constant, every 4 years there are a lot of them, then a decline in numbers follows. Meaning: Genetic drift occurs during a recession.

Genetic Drift: If the population is very small (due to a catastrophe, disease, pop wave recession), then traits persist or disappear regardless of their usefulness, by chance.

№135 Features of human populations. Number, habitats, sex and age composition. Demos. Isolates.

Peculiarities:
- large radius of individual activity

Boundaries are often social rather than geographic

Isolate - human population of up to 1500 people.

Dem - human population of 1500 to 4000 people.
Population - 7 billion - October 31, 2011

When analyzing age composition of the population It is customary to distinguish three main age groups:

In the structure of the world's population, the share of children is on average 34%, adults - 58%, the elderly - 8%.
The age structure in countries with different types of population reproduction has its own characteristics.
In countries with the first type of reproduction, the proportion of children does not exceed 22-25%, while the proportion of the elderly is 15-20% and tends to increase due to the general "aging" of the population in these countries.
In countries with the second type of population reproduction, the proportion of children is quite high. On average, it is 40-45%, and in some countries it already exceeds 50% (Kenya, Libya, Botswana). The share of the elderly population in these countries does not exceed 5-6%.

The sex composition of the world population characterized by male predominance. The number of men is 20-30 million more than the number of women. On average, 104-107 boys are born for every 100 girls. However, the differences across the countries of the world are quite significant.

The predominance of men is characteristic of most Asian countries. The preponderance of men is especially large in South and Southeast Asia (China, India, Pakistan), as well as in the Arab-Muslim countries of Southwest Asia and North Africa.

An approximately equal ratio of men and women is typical for most countries in Africa and Latin America.

The predominance of women takes place in about half of all countries in the world. It is most pronounced in Europe, which is associated with the longer life expectancy of women in these countries, as well as the large losses of the male population during the world wars.

The ratio of men and women in different age groups is different. Thus, the largest preponderance of the male population in all regions of the world is observed in the age group under 14 years. Women predominate among the elderly worldwide.

Synthetic theory of evolution

The synthetic theory of evolution - modern Darwinism - arose in the early 40s of the XX century. It is a doctrine of the evolution of the organic world, developed on the basis of data from modern genetics, ecology and classical Darwinism. The term "synthetic" comes from the title of the book by the famous English evolutionist J. Huxley "Evolution: a modern synthesis" (1942). Many scientists contributed to the development of the synthetic theory of evolution.

The main provisions of the synthetic theory of evolution can be summarized as follows:

• The material for evolution is hereditary changes - mutations (usually genes) and their combinations.
• The main driving factor of evolution is natural selection, which arises on the basis of the struggle for existence.
• The smallest unit of evolution is the population.
• Evolution is in most cases divergent in nature, i.e. one taxon can become the ancestor of several daughter taxa. (Taxon (lat. taxon; from other Greek. "order, device, organization") - a group in the classification, consisting of discrete objects, combined on the basis of common properties and characteristics. As the most significant characteristics (attributes) of a taxon in a biological taxonomists consider diagnosis, rank, and scope As classification changes, the characteristics of taxa may change (in different systems, for example, taxa of the same scope may have different diagnoses, or different ranks, or occupy a different place in the system).)
• Evolution is gradual and long lasting. Speciation as a stage of the evolutionary process is a successive change of one temporary population by a succession of subsequent temporary populations.
• A species consists of many subordinate, morphologically, physiologically, ecologically, biochemically, and genetically distinct, but reproductively non-isolated units – subspecies and populations.
• The species exists as a holistic and closed formation. The integrity of the species is maintained by migrations of individuals from one population to another, in which there is an exchange of alleles ("gene flow"),
• Macroevolution at a higher level than the species (genus, family, order, class, etc.) goes through microevolution. According to the synthetic theory of evolution, there are no patterns of macroevolution that are different from microevolution. In other words, the evolution of groups of species of living organisms is characterized by the same prerequisites and driving forces as for microevolution.
• Any real (not composite) taxon has a monophyletic origin.
• evolution has non-directional character, i.e., does not go in the direction of any final goal.

The population is the smallest of the groups of individuals capable of evolutionary development, therefore it is called the elementary unit of evolution. A single organism cannot be a unit of evolution. Evolution occurs only in a group of individuals. Since selection is based on phenotypes, individuals of this group must differ from each other, i.e. the group must be diverse. Different phenotypes under the same conditions can be provided by different genotypes. The genotype of each individual organism remains unchanged throughout life. Due to the large number of individuals, a population is a continuous flow of generations and, due to mutational variability, a heterogeneous (heterogeneous) mixture of different genotypes. The totality of genotypes of all individuals of a population - the gene pool - is the basis of microevolutionary processes in nature.

A species as an integral system cannot be taken as a unit of evolution, since species usually break up into their constituent parts - populations. That is why the role of the elementary evolutionary unit belongs to the population.

The synthetic theory of evolution revealed the underlying mechanisms of the evolutionary process, accumulated many new facts and evidence of the evolution of living organisms, and combined data from many biological sciences. Nevertheless, the synthetic theory of evolution (or neo-Darwinism) is in line with the ideas and trends that were laid by Charles Darwin.

The impetus for the development of the synthetic theory was given by the hypothesis of the recessiveness of new genes. Speaking in the language of genetics of the second half of the 20th century, this hypothesis assumed that in each reproducing group of organisms during the maturation of gametes, as a result of errors in DNA replication, mutations constantly arise - new variants of genes.

Gametes are reproductive cells that have a haploid (single) set of chromosomes and are involved in gametic, in particular, sexual reproduction. When two gametes merge in the sexual process, a zygote is formed that develops into an individual (or group of individuals) with hereditary characteristics of both parent organisms that produced gametes

The influence of genes on the structure and functions of the body is pleiotropic: each gene is involved in determining several traits. On the other hand, each trait depends on many genes; Geneticists call this phenomenon the genetic polymerization of traits. Fisher says that pleiotropy and polymerism reflect the interaction of genes, due to which the external expression of each gene depends on its genetic environment. Therefore, recombination, generating more and more new gene combinations, eventually creates such a gene environment for a given mutation that allows the mutation to manifest itself in the phenotype of the carrier individual. Thus, a mutation falls under the influence of natural selection, selection destroys combinations of genes that impede the life and reproduction of organisms in a given environment, and preserves neutral and advantageous combinations that are subjected to further reproduction, recombination and selection testing. Moreover, first of all, such gene combinations are selected that contribute to a favorable and at the same time stable phenotypic expression of initially little noticeable mutations, due to which these mutant genes gradually become dominant. This idea found expression in the work of R. Fisher "The genetic theory of natural selection" (1930). Thus, the essence of the synthetic theory is the predominant reproduction of certain genotypes and their transmission to their descendants. In the question of the source of genetic diversity, the synthetic theory recognizes the main role of gene recombination.

It is believed that the evolutionary act took place when selection retained a gene combination that was not typical for the previous history of the species. As a result, for the implementation of evolution, the presence of three processes is necessary:

• mutational, generating new variants of genes with a small phenotypic expression;
• recombination, creating new phenotypes of individuals;
• selection, which determines the compliance of these phenotypes with given living conditions or growth.

All supporters of the synthetic theory recognize the participation in the evolution of the three listed factors.

An important prerequisite for the emergence of a new theory of evolution was the book of the English geneticist, mathematician and biochemist J. B. S. Haldane, Jr., who published it in 1932 under the title "The causes of evolution". Haldane, creating the genetics of individual development, immediately included a new science in solving the problems of macroevolution.

Major evolutionary innovations very often arise on the basis of neoteny (preservation of juvenile traits in an adult organism). Neoteny Haldane explained the origin of man ("naked ape"), the evolution of such large taxa as graptolites and foraminifers. In 1933, Chetverikov's teacher N. K. Koltsov showed that neoteny is widespread in the animal kingdom and plays an important role in progressive evolution. It leads to morphological simplification, but the richness of the genotype is preserved.

In almost all historical and scientific models, 1937 was called the year of the emergence of STE - this year the book of the Russian-American geneticist and entomologist-systematist F. G. Dobzhansky "Genetics and the Origin of Species" appeared. The success of Dobzhansky's book was determined by the fact that he was both a naturalist and an experimental geneticist. “The dual specialization of Dobzhansky allowed him to be the first to throw a solid bridge from the camp of experimental biologists to the camp of naturalists” (E. Mayr). For the first time, the most important concept of "isolating mechanisms of evolution" was formulated - those reproductive barriers that separate the gene pool of one species from the gene pools of other species. Dobzhansky introduced the half-forgotten Hardy-Weinberg equation into wide scientific circulation. He also introduced the “S. Wright effect” into naturalistic material, believing that microgeographic races arise under the influence of random changes in gene frequencies in small isolates, that is, in an adaptive-neutral way.

In the English-language literature, among the creators of STE, the names of F. Dobzhansky, J. Huxley, E. Mayr, B. Rensch, J. Stebbins are most often mentioned.

The main provisions of STE, their historical formation and development

In the 1930s and 1940s, a broad synthesis of genetics and Darwinism quickly took place. Genetic ideas penetrated systematics, paleontology, embryology, and biogeography. The term "modern" or "evolutionary synthesis" comes from the title of J. Huxley's book "Evolution: The Modern synthesis" (1942). The expression "synthetic theory of evolution" in the exact application to this theory was first used by J. Simpson in 1949.

• the elementary unit of evolution is the local population;
• the material for evolution is mutational and recombination variability;
• natural selection is considered as the main reason for the development of adaptations, speciation and the origin of supraspecific taxa;
• genetic drift and the founder principle are the reasons for the formation of neutral traits;
• a species is a system of populations reproductively isolated from populations of other species, and each species is ecologically isolated;
• speciation consists in the emergence of genetic isolating mechanisms and occurs predominantly under conditions of geographic isolation.

Thus, the synthetic theory of evolution can be characterized as the theory of organic evolution by natural selection of traits determined genetically.

The activity of the American creators of STE was so high that they quickly created an international society for the study of evolution, which in 1946 became the founder of the journal Evolution. The American Naturalist again returned to publishing papers on evolutionary topics, emphasizing the synthesis of genetics, experimental and field biology. As a result of numerous and diverse studies, the main provisions of STE have not only been successfully tested, but have also been modified and supplemented with new ideas.

In 1942, the German-American ornithologist and zoogeographer E. Mayr published the book Systematics and Origin of Species, in which the concept of a polytypic species and the genetic-geographical model of speciation were consistently developed. Mayr proposed the founder principle, which he formulated in its final form in 1954. If genetic drift, as a rule, provides a causal explanation for the formation of neutral traits in the temporal dimension, then the founder principle in the spatial dimension.

After the publication of the works of Dobzhansky and Mayr, taxonomists received a genetic explanation for what they had long been sure of: subspecies and closely related species differ to a large extent in adaptive-neutral characters.

None of the works on STE can be compared with the mentioned book by the English experimental biologist and naturalist J. Huxley "Evolution: The Modern synthesis" (1942). Huxley's work surpasses even the book of Darwin himself in terms of the volume of the analyzed material and the breadth of the problematics. Huxley for many years kept in mind all directions in the development of evolutionary thought, closely followed the development of related sciences and had personal experience as an experimental geneticist.

In terms of volume, Huxley's book was unparalleled (645 pages). But the most interesting thing is that all the main ideas set forth in the book were written out very clearly by Huxley on 20 pages as early as 1936, when he sent an article to the British Association for the Advancement of Science entitled "Natural selection and evolutionary progress." In this aspect, none of the publications on evolutionary theory that appeared in the 1930s and 40s can compare with Huxley's article. Feeling well the spirit of the times, Huxley wrote: “At present, biology is in a phase of synthesis. Until that time, the new disciplines worked in isolation. There is now a tendency towards unification which is more fruitful than the old one-sided views of evolution" (1936). Already in the writings of the 1920s, Huxley showed that the inheritance of acquired characteristics is impossible; natural selection acts as a factor in evolution and as a factor in the stabilization of populations and species (evolutionary stasis); natural selection acts on small and large mutations; geographic isolation is the most important condition for speciation. The apparent purpose in evolution is explained by mutations and natural selection.

The main points of Huxley's 1936 article can be summarized very briefly in this form:

1. Mutations and natural selection are complementary processes that alone cannot create directed evolutionary change.
2. Selection in natural populations most often acts not on individual genes, but on complexes of genes. Mutations cannot be beneficial or harmful, but their selective value varies in different environments. The mechanism of action of selection depends on the external and genotypic environment, and the vector of its action on the phenotypic manifestation of mutations.
3. Reproductive isolation is the main criterion indicating the completion of speciation. Speciation can be continuous and linear, continuous and divergent, sharp and convergent.
4. Gradualism and pan-adaptationism are not universal characteristics of the evolutionary process. Most land plants are characterized by discontinuity and the rapid formation of new species. Widespread species evolve gradually, while small isolates evolve discontinuously and not always adaptively. Discontinuous speciation is based on specific genetic mechanisms (hybridization, polyploidy, chromosome aberrations). Species and supraspecific taxa, as a rule, differ in adaptive-neutral characters. The main directions of the evolutionary process (progress, specialization) are a compromise between adaptability and neutrality.
5. Potentially preadaptive mutations are widespread in natural populations. This type of mutation plays a critical role in macroevolution, especially during periods of dramatic environmental change.
6. The concept of gene action rates explains the evolutionary role of heterochrony and allometry. Synthesizing the problems of genetics with the concept of recapitulation leads to an explanation of the rapid evolution of species at the dead end of specialization. Through neoteny, the "rejuvenation" of the taxon occurs, and it acquires new rates of evolution. An analysis of the relationship between ontogenesis and phylogeny makes it possible to discover epigenetic mechanisms for the direction of evolution.
7. In the process of progressive evolution, selection acts to improve the organization. The main result of evolution was the appearance of man. With the advent of man, a great biological evolution develops into a psychosocial one. Evolutionary theory is one of the sciences that studies the formation and development of human society. It creates the foundation for understanding the nature of man and his future.

A wide synthesis of data from comparative anatomy, embryology, biogeography, paleontology with the principles of genetics was carried out in the works of I. I. Schmalhausen (1939), A. L. Takhtadzhyan (1943), J. Simpson (1944), B. Rensch (1947). Out of these studies grew the theory of macroevolution. Only Simpson's book was published in English, and during the period of the great expansion of American biology, it is most often mentioned alone among the founding works.

I. I. Shmalgauzen was a student of A. N. Severtsov, but already in the 1920s his independent path was determined. He studied the quantitative patterns of growth, the genetics of the manifestation of signs, genetics itself. One of the first Schmalhausen carried out the synthesis of genetics and Darwinism. Of the enormous legacy of I. I. Schmalhausen, his monograph “Ways and Patterns of the Evolutionary Process” (1939) stands out. For the first time in the history of science, he formulated the principle of the unity of the mechanisms of micro- and macroevolution. This thesis was not just postulated, but directly followed from his theory of stabilizing selection, which includes population-genetic and macroevolutionary components (autonomization of ontogeny) in the course of progressive evolution.

A. L. Takhtadzhyan in the monographic article “Ontogeny and Phylogeny Relationships in Higher Plants” (1943) not only actively included botany in the orbit of evolutionary synthesis, but actually built an original ontogenetic model of macroevolution (“soft saltationism”). Takhtadzhyan's model based on botanical material developed many of the remarkable ideas of A. N. Severtsov, especially the theory of archallaxis (a sharp, sudden change in an organ at the earliest stages of its morphogenesis, leading to changes in the entire course of ontogenesis). The most difficult problem of macroevolution - gaps between large taxa, was explained by Takhtadzhyan by the role of neoteny in their origin. Neoteny played an important role in the origin of many higher taxonomic groups, including flowering ones. Herbaceous plants evolved from woody plants by layered neoteny.

Neoteny (ancient Greek - young, other Greek - I stretch) is a phenomenon observed in some arthropods, worms, amphibians, as well as in many plants, in which the achievement of sexual maturity and the end of ontogenesis occurs in the early stages of development, for example , at the larval stage. In this case, the individual may or may not reach the adult stage.

A typical example of neoteny is axolotls, neotenic larvae of tailed amphibians of the genus Ambystoma, which, due to a hereditary deficiency of the thyroid hormone, remain at the larval stage. Axolotls are not inferior in size to adults. Sometimes axolotl metamorphosis occurs - with a gradual change in the conditions of existence (drying of the reservoir) or with a hormonal injection.

Neoteny is an important process from the point of view of evolution, since during it there is a loss of rigid specialization, which is more characteristic of the final stages of development than of larval ones.

In a broad sense, neoteny (juvenilization) is also understood as the manifestation in adults of traits that, under other conditions (previously in the same species, in related species, in other populations), are characteristic of children. For example, a human (Homo sapiens) differs from the great apes in the structure of the hairline (hairy areas in humans coincide with those in the fetus of great apes), as well as late ossification (including the skull). Incomplete ossification is a juvenile characteristic. Due to the late ossification of the skull, restrictions on brain growth are softened.

Back in 1931, S. Wright proposed the concept of random gene drift, which speaks of the absolutely random formation of the deme gene pool as a small sample from the gene pool of the entire population. Initially, genetic drift turned out to be the very argument that was missing for a very long time in order to explain the origin of non-adaptive differences between taxa. Therefore, the idea of ​​drift immediately became close to a wide range of biologists. J. Huxley called the drift "the Wright effect" and considered it "the most important of recent taxonomic discoveries." George Simpson (1948) based his hypothesis of quantum evolution on drift, according to which a population cannot independently move out of the zone of attraction of an adaptive peak. Therefore, in order to get into an unstable intermediate state, a random, selection-independent genetic event is needed - genetic drift. It is a prerequisite and driving force of evolution from the standpoint of synthetic theory.

An allele is a different form of the same gene located in the same regions (loci) of homologous chromosomes and determines alternative variants of the development of the same trait. In a diploid organism, there can be two identical alleles of the same gene, in which case the organism is called homozygous, or two different, resulting in a heterozygous organism.

It is known that under certain conditions, the allele frequency in the gene pool of a population remains constant from generation to generation. Under these conditions, the population will be in a state of genetic equilibrium and no evolutionary changes will occur. Therefore, for the implementation of evolutionary processes, the presence of factors supplying evolutionary material, i.e., leading to genetic variability in the population structure, is necessary. This role is played by the mutation process, combinative variability, gene flow. periodic fluctuations in the number of populations (population waves, or waves of life), genetic drift. Having a different nature, these factors act randomly and undirectedly and lead to the appearance of various genotypes in the population. Important for evolution are the factors that ensure the emergence of barriers that prevent free interbreeding. These are various forms of isolation that violate panmixia (free crossing of organisms) and perpetuate any differences in the sets of genotypes in different parts of the population.

Gene mutations are the main source of new alleles in a population. The frequency of occurrence of new mutations is usually low: 1 * 10-6–1 * 10-5 (one mutation per 10 thousand - 1 million individuals [gametes] per generation). However, due to the large number of genes (in higher forms, for example, there are tens or thousands of them), the overall frequency of all emerging mutations in living organisms is quite high. In some species, 10 to 25% of individuals (gametes) per generation carry mutations. In most cases, the occurrence of mutations reduces the viability of individuals compared to parental forms. However, upon transition to a heterozygous state, many mutations not only do not reduce the viability of individuals bearing them, but also increase it (the phenomenon of inbreeding and subsequent heterosis when crossing inbred lines). Some mutations may turn out to be neutral, and a small percentage of mutations from the very beginning even leads, under certain conditions, to an increase in the viability of individuals. No matter how small the proportion of such mutations may be, they can play a significant role in the grandiose time scales of the evolutionary process. However, it should be noted that mutations by themselves do not lead to the development of a population or species. They are only material for the evolutionary process. Without other factors of evolution, the mutation process cannot provide a directed change in the gene pool of the population.

A certain contribution to the violation of the genetic balance in populations is made by combinative variability. Having arisen, individual mutations are in the vicinity of other mutations, are part of new genotypes, i.e. many combinations of alleles and non-allelic interactions appear.

An important source of genetic diversity in populations is gene flow - the exchange of genes between different populations of the same species due to the migration of individuals from population to population. In this case, the genes of migrating individuals are included in the gene pool of the population when crossing. As a result of such crosses, the genotypes of the offspring differ from the genotypes of the parents. In this case, gene recombination occurs at the interpopulation level.

Population sizes, both spatially and in number of individuals, are subject to constant fluctuations. The reasons for these fluctuations are diverse and in general form are reduced to the influence of biotic and abiotic factors (food supplies, the number of predators, competitors, pathogens of infectious diseases, climatic conditions of the year, etc.). For example, an increase in the number of hares (food) after a while leads to an increase in the number of wolves and lynxes that feed on hares; high yields of spruce cones in a dry warm summer have a positive effect on the growth of the squirrel population. Fluctuations in the number of populations in nature are of a periodic nature: after an increase in the number of individuals, its regular decrease occurs, etc. S. S. Chetverikov (1905) called such periodic fluctuations in the number of individuals in populations “waves of life” or “population waves”.

The waves of life have an impact on the change in the genetic structure of populations. With an increase in the population, the probability of the appearance of new mutations and their combinations increases. If, on average, there is one mutation per 100 thousand individuals, then with an increase in the population size by 10 times, the number of mutations will also increase by 10 times. After a decline in population, the surviving part of the individuals of the population will differ significantly in genetic composition from the previously numerous population: some of the mutations will completely accidentally disappear along with the death of the individuals carrying them, and some mutations will also accidentally increase their concentration. With a subsequent increase in the population, the gene pool of the population will turn out to be different, since the number of individuals carrying mutations will naturally increase in it. Thus, population waves do not in themselves cause hereditary variability, but they contribute to a change in the frequency of mutations and their recombinations, i.e. change in the frequencies of alleles and genotypes in the population. Thus, population waves are a factor supplying material for evolution.

Genetic drift also influences the genetic structure of a population. This process is typical for small populations, where not all alleles typical for a given species may be represented. Random events, such as the premature death of an individual that was the only owner of an allele, will lead to the disappearance of this allele from the population. Just as an allele can disappear from a population, its frequency can randomly increase. This random change in the concentration of alleles in a population is called genetic drift.

Genetic drift is unpredictable. It can lead to the death of a small population, but it can make it even more adapted to a given environment or increase its divergence from the parent population.

Thus, genetic diversity in populations is achieved by the combined influence of mutations, their combinations, life waves, gene flow and gene drift.

Soon after S. Wright formulated his concept, enthusiasm for genetic drift waned. The reason is intuitively clear: any completely random event is unique and unverifiable. The wide citation of the works of S. Wright in modern evolutionary textbooks, which present an exclusively synthetic concept, cannot be explained otherwise than by the desire to illuminate the whole variety of views on evolution, ignoring the relationship and difference between these views.

The ecology of populations and communities entered the evolutionary theory due to the synthesis of the Gause law and the genetic-geographical model of speciation. Reproductive isolation has been supplemented by ecological niche as the most important species criterion. At the same time, the niche approach to species and speciation turned out to be more general than the purely genetic approach, since it is also applicable to species that do not have a sexual process.

The entry of ecology into the evolutionary synthesis was the final stage in the formation of the theory. From that moment, the period of using STE in the practice of taxonomy, genetics, and selection began, which lasted until the development of molecular biology and biochemical genetics.

With the development of the latest sciences, STE began to expand and modify again. Perhaps the most important contribution of molecular genetics to the theory of evolution was the division of genes into regulatory and structural ones (the model of R. Britten and E. Davidson, 1971). It is the regulatory genes that control the emergence of reproductive isolating mechanisms that change independently of enzyme genes and cause rapid changes (on a geological time scale) at the morphological and physiological levels.

The idea of ​​a random change in gene frequencies has found application in the theory of neutrality (Motoo Kimura, 1985), which goes far beyond the traditional synthetic theory, being created on the foundation of not classical, but molecular genetics. Neutralism is based on a completely natural position: not all mutations (changes in the DNA nucleotide series) lead to a change in the amino acid sequence in the corresponding protein molecule. Those amino acid substitutions that have taken place do not necessarily cause a change in the shape of the protein molecule, and when such a change does occur, it does not necessarily change the nature of the activity of the protein. Consequently, many mutant genes perform the same functions as normal genes, which is why selection behaves completely neutrally towards them. For this reason, the disappearance and fixation of mutations in the gene pool depend purely on chance: most of them disappear soon after their appearance, a minority remain and can exist for quite a long time. As a result, selection that evaluates phenotypes "essentially makes no difference what genetic mechanisms determine the development of a given form and corresponding function, the nature of molecular evolution is completely different from that of phenotypic evolution" (Kimura, 1985).

The last statement, reflecting the essence of neutralism, is in no way consistent with the ideology of the synthetic theory of evolution, which goes back to the concept of A. Weismann's germ plasm, from which the development of the corpuscular theory of heredity began. According to Weisman's views, all factors of development and growth are located in germ cells; accordingly, in order to change the organism, it is necessary and sufficient to change the germ plasm, that is, the genes. As a result, the theory of neutrality inherits the concept of genetic drift, generated by neo-Darwinism, but subsequently abandoned by it.

The latest theoretical developments have appeared, which made it possible to bring STE even closer to real-life facts and phenomena that its original version could not explain. The milestones achieved by evolutionary biology to date differ from the previously presented postulates of STE:

1. The postulate of the population as the smallest evolving unit remains valid. However, a huge number of organisms without a sexual process remain outside the scope of this definition of a population, and this is seen as a significant incompleteness of the synthetic theory of evolution.
2. Natural selection is not the only driver of evolution.
3. Evolution is not always divergent.
4. Evolution does not have to be gradual. It is possible that in some cases individual macroevolutionary events may also have a sudden character.
5. Macroevolution can go both through microevolution and along its own paths.
6. Recognizing the insufficiency of the reproductive criterion of a species, biologists are still unable to offer a universal definition of species for both forms with a sexual process and for agamic forms.
7. The random nature of mutational variability does not contradict the possibility of the existence of a certain canalization of evolutionary paths that arises as a result of the past history of the species. The theory of nomogenesis or evolution based on regularities, put forward in 1922-1923, should also become widely known. L.S. Berg. His daughter R. L. Berg considered the problem of randomness and patterns in evolution and came to the conclusion that “evolution proceeds along permitted paths” (R. L. Berg, Genetics and Evolution, Selected Works, Novosibirsk, Nauka, 1993, p. .283).
8. Along with monophyly, paraphilia is widely recognized.
9. A certain degree of predictability is also a reality, the possibility of predicting the general directions of evolution (the provisions of the latest biology are taken from: Nikolai Nikolaevich Vorontsov, 1999, pp. 322 and 392–393).

We can say that the development of SHE will continue with the advent of new discoveries in the field of evolution.

Criticism of the synthetic theory of evolution. The synthetic theory of evolution is not in doubt among most biologists: it is believed that the process of evolution as a whole is satisfactorily explained by this theory.

One of the criticized general provisions of the synthetic theory of evolution is its approach to explaining secondary similarities, that is, close morphological and functional characters that were not inherited, but arose independently in phylogenetically distant branches of the evolution of organisms.

According to neo-Darwinism, all the signs of living beings are completely determined by the genotype and the nature of selection. Therefore, parallelism (secondary similarity of related beings) is explained by the fact that organisms have inherited a large number of identical genes from their recent ancestor, and the origin of convergent traits is entirely attributed to the action of selection. However, it is well known that similarities that develop in fairly distant lineages are often maladaptive and therefore cannot be plausibly explained either by natural selection or by common inheritance. The independent occurrence of identical genes and their combinations is obviously excluded, since mutations and recombination are random processes.

In response to such criticism, supporters of the synthetic theory may object that the ideas of S. S. Chetverikov and R. Fisher about the complete randomness of mutations have now been significantly revised. Mutations are random only in relation to the environment, but not to the existing organization of the genome. Now it seems quite natural that different sections of DNA have different stability; accordingly, some mutations will occur more often, others less frequently. In addition, the set of nucleotides is very limited. Consequently, there is a possibility of independent (and, moreover, completely random, causeless) occurrence of the same mutations (up to the synthesis of one and similar proteins by distant species of one and similar proteins that could not have been inherited by them from a common ancestor). These and other factors cause significant secondary recurrence in the structure of DNA and can explain the origin of non-adaptive similarity from the standpoint of neo-Darwinism as a random selection from a limited number of possibilities.

Another example is the criticism of STE by proponents of mutational evolution, which is related to the concept of punctualism or "punctuated equilibrium". Punctualism is based on a simple paleontological observation: the duration of stasis is several orders of magnitude longer than the duration of the transition from one phenotypic state to another. Judging by the available data, this rule is generally true for the entire fossil history of metazoans and has a sufficient amount of evidence.

The authors of punctualism oppose their view to gradualism - Darwin's idea of ​​gradual evolution through small changes - and consider punctuated equilibrium a sufficient reason to reject the entire synthetic theory. Such a radical approach caused a discussion around the concept of punctuated equilibrium, which has been going on for 30 years. Most authors agree that there is only a quantitative difference between the concepts of “gradual” and “intermittent”: a long process appears as an instantaneous event, being depicted on a compressed time scale. Therefore, punctualism and gradualism should be considered as additional concepts. In addition, supporters of the synthetic theory rightly note that punctuated equilibrium does not create additional difficulties for them: long-term stasis can be explained by the action of stabilizing selection (under the influence of stable, relatively unchanged conditions of existence), and rapid change can be explained by S. Wright's theory of shifting equilibrium for small populations , with abrupt changes in the conditions of existence and / or in the case of the passage of a species or any of its isolated parts, populations, through the bottleneck.

Genome variations in response to environmental challenges. In the theory of evolution and in genetics, the question of the connection between hereditary changes and the direction of selection has always been discussed. According to Darwinian and post-Darwinian ideas, hereditary changes occur in different directions and only then are picked up by selection. Particularly clear and convincing was the replica method invented in the early 1950s by the Lederbergs. With the help of a velvet cloth, they obtained exact copies - prints - of an experimental sowing of bacteria on a Petri dish. Then, one of the plates was used for selection for phage resistance and the topography of the points of appearance of resistant bacteria on the plate with phage and in the control was compared. The arrangement of phage-resistant colonies was the same in the two replica dishes. The same result was obtained in the analysis of positive mutations in bacteria defective in any metabolite.

Discoveries in the field of mobile genetics have shown that the cell as an integral system in the course of selection can adaptively rearrange its genome. It is able to respond to the challenge of the environment with an active genetic search, and not passively wait for the random occurrence of a mutation that allows it to survive. And in the experiments of the Lederberg spouses, the cells had no choice: either death or an adaptive mutation.

In cases where the selection factor is not lethal, gradual rearrangements of the genome are possible, directly or indirectly related to the conditions of selection. This became clear with the discovery in the late 1970s of a gradual increase in the number of loci in which genes for resistance to a selective agent that blocks cell division are located. It is known that methotrexate, an inhibitor of cell division, is widely used in medicine to stop the growth of malignant cells. This cell poison inactivates the enzyme dihydrofolate reductase (DHFR), which is controlled by a specific gene.

The resistance of Leishmania cells to the cytostatic poison (methotrexate) increased stepwise, and the proportion of amplified segments with the resistance gene increased proportionally. Not only the selected gene was multiplied, but also the large DNA regions adjacent to it, called amplicons. When resistance to poison in Leishmania increased 1000-fold, amplified extrachromosomal segments made up 10% of the DNA in the cell! It can be said that a pool of facultative elements was formed from one obligate gene. There was an adaptive rearrangement of the genome during selection.

If the selection continued long enough, some of the amplicons were inserted into the original chromosome, and after the selection was stopped, the increased resistance persisted.

With the removal of the selective agent from the medium, the number of amplicons with the resistance gene gradually decreased in a number of generations, and resistance simultaneously decreased. Thus, the phenomenon of long-term modifications was modeled, when massive changes caused by the environment are inherited, but gradually fade away in a number of generations.

During repeated selection, a part of the amplicons remaining in the cytoplasm ensured their rapid autonomous replication, and resistance arose much faster than at the beginning of the experiments. In other words, a kind of cellular amplicon memory of past selection was formed on the basis of preserved amplicons.

If we compare the method of replicas and the course of selection for resistance in the case of amplification, then it turns out that it was the contact with the selective factor that caused the transformation of the genome, the nature of which correlated with the intensity and direction of selection.

Discussion about adaptive mutations. In 1988, an article by J. Cairns and co-authors appeared in the journal Nature on the occurrence of selection-dependent "directed mutations" in the bacterium E. coli. We took bacteria carrying mutations in the lacZ gene of the lactose operon, unable to break down the disaccharide lactose. However, these mutants could divide on a medium with glucose, from where, after one or two days of growth, they were transferred to a selective medium with lactose. Having selected lac+ reverses, which, as expected, arose in the course of “glucose” divisions, non-growing cells were left under conditions of carbohydrate starvation. First, the mutants died off. But after a week or more, a new growth was observed due to an outbreak of reversions in the lacZ gene. It was as if cells under severe stress, without dividing (!), were conducting a genetic search and adaptively changing their genome.

In subsequent works by B. Hall, bacteria mutated in the tryptophan utilization gene (trp) were used. They were placed on a medium devoid of tryptophan, and the frequency of reversions to the norm was assessed, which increased precisely during tryptophan starvation. However, the starvation conditions themselves were not the cause of this phenomenon, because on the medium with starvation for cysteine, the frequency of reversions to trp+ did not differ from the norm.

In the next series of experiments, Hall took double tryptophan-deficient mutants carrying both mutations in the trpA and trpB genes, and again placed the bacteria on a medium devoid of tryptophan. Only individuals in which reversions occurred simultaneously in two tryptophan genes could survive. The frequency of occurrence of such individuals was 100 million times higher than expected with a simple probabilistic coincidence of mutations in two genes. Hall preferred to call this phenomenon "adaptive mutations" and subsequently showed that they also occur in yeast, i.e. in eukaryotes.

The publications of Cairns and Hall immediately sparked a heated discussion. The result of its first round was the presentation of one of the leading researchers in the field of mobile genetics J. Shapiro. He briefly discussed two main ideas. First, the cell contains biochemical complexes, or “natural genetic engineering” systems, that are capable of remodeling the genome. The activity of these complexes, like any cellular function, can change dramatically depending on the physiology of the cell. Secondly, the frequency of occurrence of hereditary changes is always estimated not for one cell, but for a cell population in which cells can exchange hereditary information with each other. In addition, intercellular horizontal transfer with the help of viruses or the transfer of DNA segments is enhanced under stressful conditions. According to Shapiro, these two mechanisms explain the phenomenon of adaptive mutations and return it to the mainstream of conventional molecular genetics. What, in his opinion, are the results of the discussion? “We found a genetic engineer there with an impressive set of intricate molecular tools for reorganizing the DNA molecule” (Shapiro J. // Science. 1995. V.268. P.373–374).

In recent decades, an unforeseen realm of complexity and coordination has been opened up at the cellular level that is more compatible with computer technology than with the mechanized approach that dominated the creation of the neo-Darwinian modern synthesis. Following Shapiro, at least four groups of discoveries can be named that have changed the understanding of cellular biological processes.

1. Organization of the genome. In eukaryotes, genetic loci are arranged according to a modular principle, representing constructions of regulatory and coding modules common to the entire genome. This ensures the rapid assembly of new constructs and the regulation of gene assemblies. The loci are organized into hierarchical networks, led by a master switch gene (as in the case of sex regulation or eye development). Moreover, many of the subordinate genes are integrated into different networks: they function at different periods of development and affect many traits of the phenotype.

2. Reparative possibilities of the cell. Cells are by no means passive victims of random physical and chemical influences, since they have a system of reparations at the level of replication, transcription and translation.

3. Mobile genetic elements and natural genetic engineering. The work of the immune system is based on the continuous construction of new variants of immunoglobulin molecules based on the action of natural biotechnological systems (enzymes: nucleases, ligases, reverse transcriptases, polymerases, etc.). These same systems use mobile elements to create new inherited structures. At the same time, genetic changes can be massive and ordered. Reorganization of the genome is one of the main biological processes. Natural genetic engineering systems are regulated by feedback systems. For the time being, they are inactive, but at key times or during times of stress, they are activated.

4. Cellular information processing. Perhaps one of the most important discoveries in cell biology is that the cell continuously collects and analyzes information about its internal state and external environment, making decisions about growth, movement and differentiation. Particularly indicative are the mechanisms of control of cell division, which underlie growth and development. The process of mitosis is universal in higher organisms and includes three successive stages: preparation for division, chromosome replication, and completion of cell division. The analysis of the gene control of these phases led to the discovery of special points at which the cell checks whether the repair of damages in the DNA structure occurred at the previous stage or not. If the errors are not corrected, the subsequent stage will not start. When the damage cannot be eliminated, a genetically programmed system of cell death, or apoptosis, is launched.

Under the conditions of the call of the environment, the cell acts purposefully, like a computer, when, when it is started, the normal operation of the main programs is checked step by step, and in the event of a malfunction, the computer stops. In general, it becomes obvious, already at the level of the cell, that the unconventional French evolutionary zoologist Paul Grasset is right: “To live means to react, and by no means to be a victim.”

Ways of occurrence of natural hereditary changes in the environment-facultative elements-obligate elements system. Facultative elements are the first to perceive non-mutagenic environmental factors, and the variations that arise then cause mutations. Obligatory elements also affect the behavior of optional elements.

Non-canonical hereditary changes arising under the influence of selection for cytostatics and leading to gene amplification.

Macromutational evolution

The crown of the general evolutionary concept is considered to be the synthetic theory of evolution (STE). It attempted to combine with Darwinian gradualism and natural selection classical genetics, which initially diverged rather sharply from them.

At the same time, views were gradually taking shape in foreign and domestic science that contradicted the synthetic theory of evolution or significantly modified it (often at the philosophical and biological level).

In domestic biology, there are three milestones in the formation of non-Darwinian views on the processes of evolution. The first is L.S. Berg's concept of nomogenesis, formulated in the 1920s. It consists in postulating other drivers of evolution than those formulated by Darwin and the supporters of STE: instead of monophyly - polyphilia, instead of gradualness - spasmodicity, instead of randomness - regularity. At the same time, Lamarckian views were spreading in the USSR, attractive to Marxist ideology and explaining evolution by the inheritance of acquired traits in order to patch up the holes that existed in the evolutionary concept. With the development of genetics, which proved the inconsistency of this principle, such views gradually died out (in the 1950s and 1960s they were revived by O. Lepeshinskaya and T. Lysenko).

Recently, some Western biologists (mainly working with bacteria and protozoa) are trying to return to the hypothesis of the inheritance of acquired characters. Their ideas are based on epigenetic inheritance in protozoa and bacteria (it has long been known and is observed in the differentiation of cells in multicellular organisms). In fact, such views are based on a misunderstanding of the concepts that the authors operate with. Indeed, one can talk about the inheritance of acquired traits only if we are talking about organisms whose cells are divided into somatic and sexual, and when the trait acquired by the former is transmitted in an unknown way and fixed in the genome of the latter. For example, if a bodybuilding fan builds up his biceps to an unprecedented size with the help of special exercises, then, in accordance with the neo-Lamarckian views, the genome of his germ cells must somehow learn about this and record information; then the descendants of this subject should have such muscles without any training. So far, the existence of such a mechanism is not visible. References to genetic imprinting are not valid - with equal success, ordinary mutations can be called the inheritance of acquired traits. The body has acquired them! In other words, whether the new Lamarckists want it or not (most likely they don't!), the consistent implementation of their point of view in a direct way leads to the denial of the basic postulates of modern genetics, i.e. to Lysenkoism, a completely different paradigm that does not have any reliable experimental foundations.

The next stage in the formation of non-Darwinian views is associated with Yu.P. Altukhov and N.N. Vorontsov (60–70s). The first one, echoed in the West by A. Carson (1975), divided the genome into polymorphic and monomorphic and put forward a hypothesis according to which polymorphism and the part of the genome that provides it contribute to the constancy of the species, expand its adaptive capabilities and, accordingly, the distribution area. Speciation, however, occurs due to an abrupt change in the monomorphic part of the genome (Altukhov Yu.P. Genetic processes in populations. M., 1983).

Vorontsov formulated the concept of mosaic evolution and developed the doctrine of the role of macromutations and seismic factors in phylogenesis (Vorontsov N.N. Development of evolutionary ideas in biology. M., 1999), as well as rapid speciation due to changes in the structure of chromosomes.

The third stage (80–90s) is marked by the discovery of the Tomsk geneticist VN Stegniy. He demonstrated the species-specific attachment points of polytene (in the form of a bundle of chromosome threads) of insect chromosomes to the nuclear membrane and proved the absence of polymorphism for this trait (Stegniy V.N. Genome architectonics. Systemic mutations and evolution. Novosibirsk, 1991). Therefore, speciation according to the principle of gradual change in gene frequencies postulated by STE is excluded in this case and should occur by macromutations.

Proponents of macromutational evolution have always attached great importance to the unity of historical and individual development (Korochkin L.I. Introduction to developmental genetics. M., 1999), which was discussed immediately after the creation of evolutionary theory. After all, evolutionary transformations could not begin otherwise than through changes in the program of individual development.

Initially, this unity was expressed in the so-called biogenetic law. Based on the works of I. Meckel and C. Darwin, the German biologist F. Müller already in 1864 pointed out a close connection between the embryonic development of ancestors and the embryogenesis of descendants. This idea was transformed into a biogenetic law by the famous Darwinist E. Haeckel, who in 1866 formulated it as follows: “Ontogeny is a short and quick repetition of phylogeny, a repetition determined by the physiological functions of heredity (reproduction) and fitness (nutrition).”

The most prominent embryologists of that time (A. Kelliker, V. Gies, K. Baer, ​​O. Gertwig, A. Sedgwick) critically perceived the ideas of Müller-Haeckel, believing that something new in ontogenesis does not arise due to the addition of new stages to the ontogeny of ancestors, but due to such a change in the course of embryogenesis, which transforms ontogenesis as a whole. In 1886, W. Kleinenberg suggested that such seemingly functionless embryonic structures as the notochord or tubular anlage of the heart in vertebrates, which were considered examples of recapitulation (i.e., the repetition in the embryogenesis of modern organisms of the signs that their adult ancestors had ), take part in the formation of later structures. One of the founders of American embryology S. Whitman prophetically wrote in 1895 that our eyes are similar to the eyes of our ancestors not because of genealogical connections, but because the molecular processes that determine their morphogenesis occurred under similar conditions.

Finally, such a phenomenon as preadaptation has long been known. Even Baer noted that if the biogenetic law were true, then in the embryogenesis of lower organized animals in a passing state, formations inherent only in higher forms would not be observed. There are many such examples. Thus, in all mammals, the jaws at the very beginning of development are as short as in humans, and the brain of birds during the first third of embryogenesis is much closer to the brain of mammals than in the adult state. Back in 1901, the Russian paleontologist A.P. Pavlov showed that young specimens of some ammonites have features that disappear in adulthood, but are found in higher forms.

In the 1920s and 1930s, the criticism of the biogenetic law was continued by Sedgwick's student F. Garstang, who argued that ontogenesis does not repeat phylogenesis, but creates it. Garstang was supported by L. Bertalanffy and T. Morgan, who, in particular, noted that in the course of evolution, embryonic stages can change and lose similarity with the corresponding stages of earlier forms. Therefore, if the theory of recapitulation is a law, then it has so many exceptions that it becomes useless and often erroneous. Understanding the seriousness of these objections and nevertheless striving to save the biogenetic law, the outstanding Russian biologist A.N. Severtsov put forward the theory of phylembryogenesis, according to which embryonic changes are associated with the phylogenetic development of an adult organism (Severtsov A.N. Morphological directions of the evolutionary process. M ., 1967). He identified three types of phylembryogenesis: end-stage extension (for example, the development of jaws in garfish); change in the developmental path (development of scales in shark fish and reptiles); change in primary roots.

However, Severtsov's pioneering work did not put an end to the criticism of Haeckel-Muller's ideas. Paleontologist Sh. Depere, zoologist A.A. Lyubishchev, embryologists D. Dewor, S.G. Kryzhanovsky, physiologist I.A.

Thus, Dewar noted that the alimentary canal of the embryo is closed for some time (ie, not connected with either the mouth or the anus), and this can hardly make sense at any ancestral stage. The formation of the single-toed limb of a horse from the very beginning reveals a clear specificity: the loss of lateral toes in the course of evolution is not repeated in the ontogeny of this animal. Lost fingers are reduced in the earliest embryonic anlage (Dewar D. Difficulties of the evolution theory. L., 1931).

Comparative embryological studies also speak of similar contradictions. The formation of the body plan of various organisms in ontogeny is due to changes in the expression of segmentation genes and homeotic genes. The stage at which the highest morphological similarity in embryos of one branch is called phylotypic. The stage at which differences in terms of body structure appear in animals of different branches, associated with the work of homeotic genes, is designated as zootypic.

For example, chordates go through a developmental stage in which they have a similar structure of the neural tube, notochords and somites. This is the phylotype point at which the regional identity of the expression of homeotic genes is established. Despite the conservatism of the phylotypic and zootypic stages, developmental geneticists determine that the initial stages of embryogenesis within each branch are diverse. For example, human, chicken, and zebrafish embryos are similar at the phylotype stage, while at earlier stages of development they are completely different morphologically, which is in conflict with the biogenetic law.

Do morphological and morphogenetic differences reflect any corresponding molecular genetic specificity? The available factual material suggests that the molecular genetic "machine" is similar in all cases, and morphological differences are due to shifts in the temporal sequence of the same molecular processes. They determine the morphogenesis of different taxa.

This can be seen in the evolution of insects. Thus, in Drosophila, a complete set of body segments is established by the end of the blastoderm stage. Embryos of such insects (flies, bees) are called embryos with a long bookmark. In the grasshopper, the syncytium and cellular blastoderm are formed, as in Drosophila, but only a small fraction of the blastoderm (embryonic bookmark) is involved in the development of the embryo, and the rest of it gives rise to embryonic membranes. In this case, the plan of the animal's structure in the embryonic anlage is not presented in full. Only the head region arises from it, while other parts develop from the growth zone. Such embryos are called short-term embryos. There is also an intermediate type of development, when the head and chest develop from the embryonic anlage, and the abdominal region later from the growth zone. Such phenomena are not easy to reconcile with the biogenetic law, and therefore skepticism towards it is understandable.

However, in the domestic literature on evolutionary biology, there is still a serious attitude to the biogenetic law, and in Western literature it is usually not mentioned at all or denied. A vivid example of this is the book by R. Raff and T. Kaufman (Raff R., Kaufman T. Embryos, genes, evolution. M. 1986), who believe that “the weaknesses of the biogenetic law were in its dependence on the Lamarckian theory of heredity and in its an indispensable condition that a new evolutionary stage can only be reached as an addition to the adult stage of the immediate ancestor. And again: “Together, Mendelian genetics, the isolation of germline cells and the importance of morphological characters throughout development put an end to the theory of recapitulation ...”

This is, of course, an extreme position, but it is popular in the West. However, we have no reason to doubt that the individual and historical development of organisms are closely related, since any evolutionary transformation is based on certain genetically determined shifts in ontogeny. Consequently, they constitute a kind of unity, in assessing which one should proceed from the fact that both individual and evolutionary development are based on the same material, namely DNA, and therefore GENERAL regularities must be inherent in them.

It is unlikely that the hereditary information contained in DNA unfolds in ontogenesis and phylogenesis in a fundamentally different way. However, this assumption is now generally accepted. It is believed that phylogenesis is carried out on the basis of inexpedient, undirected processes and is based on the gradual accumulation of random, small mutations in a population. But, based on the principle of unity, it is more reasonable and logical to extend the experimentally proven features of ontogenesis to the evolutionary events caused by them, which, as a rule, cannot be accurately verified, and therefore are formulated as speculative, pulled up under one or another experimentally unverifiable concept.

When extrapolating data from developmental genetics to phylogenetic processes, it is necessary to rely on the following facts.

First, ontogeny is subordinated to a specific goal - transformation into an adult organism - and, therefore, is expedient. From this follows the expediency of the evolutionary process, as long as it depends on the same material - DNA.

Secondly, the process of ontogeny is not accidental; it proceeds in a directed manner from stage to stage. Any kind of accident excludes the exact realization of the plan of normal development. Why, then, should evolution be based on random mutations and go in an unknown direction along an “undirected” path? Looking closely at various evolutionary series and seeing similar formations in them (wings in birds, bats, insects, ancient reptiles, the similarity of wings in some fish), you begin to suspect the presence of phylogenesis programmed in the DNA structure itself (as well as ontogenesis), as if directed through some “preformed” channel, as Berg spoke about in the theory of nomogenesis.

Finally, in the course of ontogenesis, phases of relatively calm development are replaced by the so-called critical periods, which are distinguished by the morphogenetic activity of the nuclei and the activation of morphogenesis. It is obvious (and this is confirmed) that in evolution long phases of dormancy are replaced by bursts of speciation. In other words, it does not have a gradualist, but a spasmodic character.

Embryologists have long considered evolution not as the result of the accumulation of small mutations, gradually leading to the formation of a new species through intermediate forms, but as a consequence of sudden and radical transformations in ontogeny, immediately causing the emergence of a new species. Even E. Rabo in 1908 assumed that speciation is associated with large-amplitude mutations that manifest themselves at the early stages of morphogenesis and violate the complex system of ontogenetic correlations.

E. Guillenot believed that J. Buffon was close to the truth when, describing the ridiculous structure and shape of the beak, characteristic of some species of birds, he ranked them as teratological (ugly) deviations, hardly compatible with life. Noticing that the same deformities in some groups of invertebrates (for example, echinoderms) appear either as random individual features or as permanent features of species, genera and families, he suggested that some catastrophic deformities are the consequences of macromutations that change the course of ontogenesis. For example, the inability to fly in many birds of open spaces (epiornis, ostriches, cassowaries) arose as a deformity that dooms its carriers to the only way of life in a limited biotope. Baleen whales are a real paradox of nature and a living collection of deformities. Guillenot believes that any animal can be described in terms of teratology. So, the front paws of a mole are an example of achondroplasia (impaired ossification of the long bones of the limbs), whales have bilateral ectromelia (congenital absence of limbs). In humans, the anatomical features associated with the vertical position of the body, the absence of a tail, a continuous hairline, etc., can be considered as a deformity in comparison with its ancestors.

The Belgian embryologist A. Dalk suggested that since the Cambrian time, due to radical transformations of the earliest stages of embryogenesis, two to three dozen basic structural plans (archetypes) have been established. Abrupt changes in the structure, if they happened in an adult, would have turned into a catastrophe for him and doomed him to death, and the embryos, due to their extreme plasticity and high regulatory ability, could endure them. He believed that the basis of evolution is an event (called by him ontomutation), which manifests itself in radical and at the same time viable transformations in the cytoplasm of the egg as a morphogenetic system.

R. Goldschmidt formulated the provisions on the phylogenetic role of sharp deviations in embryonic development with particular clarity in his concept of macroevolution. It includes several postulates:

• macroevolution cannot be understood on the basis of the hypothesis of the accumulation of micromutations, it is accompanied by the reorganization of the genome;
• changes in chromosomal structure can cause a significant phenotypic effect regardless of point mutations;
• changes based on the transformation of systems of intertissue interactions in ontogenesis may have evolutionary significance - they cause the appearance of so-called promising freaks that deviate from the norm in their structure, but are able to adapt to certain environmental conditions and give rise to new taxonomic units;
• systemic reorganization of ontogeny is realized either through the effects of modifier genes, or due to macromutations that significantly change the functioning of the endocrine glands, which produce various hormones that affect the development of the organism as a whole.

As an example of the phenotypic effects caused by hormones, Goldschmidt cites acromegaly, gigantism, and dwarfism. S. Stockard connects many racial traits in dogs with the function of the endocrine glands, and D.K. Belyaev demonstrated significant changes in the function of the endocrine glands during the domestication of foxes.

Experiments carried out in the early 1930s on fish from the family of mudskippers Peryophthalmus megaris showed that a three-year continuous administration of the hormone thyroxin causes significant morphogenetic changes. In this case, the pectoral fins lengthen, which acquire an external resemblance to the limbs of amphibians, and the normally scattered endocrine elements that produce thyroxine are grouped into more compact formations similar to the structures characteristic of amphibians. These facts allowed Goldschmidt to draw a conclusion about the significant phenotypic effect of those changes in the genome that affect the mechanisms of hormonal control. Vorontsov, who shared the views of Goldschmidt, presented two indisputable facts of the macromutational emergence of hairless mammalian species due to a single macromutation of the hairless type. These data contradict the concept of obligate gradualism.

One of the largest paleontologists of our time, O. Schindewolf, also believing that ontogenesis precedes phylogeny, proposed the theory of typostrophism. He ignored population processes, rejected the evolutionary role of chance and recognized the individual as the bearer of evolution. The absence of intermediate forms in the paleontological record was explained by the rapid transformation of forms due to sharp changes in the level of cosmic and solar radiation. He also owns the catchphrase: "The first bird flew out of the reptile's egg."

Diagram of embryonic development and structure of the eye in cephalopods (above) and vertebrates. 1 - retina, 2 - pigment membrane, 3 - cornea, 4 - iris, 5 - lens, 6 - ciliary (epithelial) body, 7 - choroid, 8 - sclera, 9 - optic nerve, 10 - integumentary ectoderm, 11 - brain. On the basis of completely different morphogenetic processes, similar organs are formed. It is in this way that the convergent development of characters in phylogenetically unrelated organisms can be carried out. At the heart of the events that consistently build this structure is, obviously, a genetically programmed development plan. The successive unfolding of these events is regulated by a complex and finely tuned genetic mechanism, which can be initiated by a single Goldschmidt macromutation.

Similar views called the theory of punctuated equilibrium are professed by American paleontologists N. Eldridge, S. Stanley and S. Gould. They attach great importance in evolution to paedomorphosis, when ontogenesis is shortened due to the loss of the adult stage and animals are able to reproduce at the larval stage. Apparently, in this way some groups of tailed amphibians (Proteus, sirenaceae), appendicularia, insects (cricket-crickets grilloblattids), arachnids (a number of soil mites) arose (Nazarov V.I. Doctrine of macroevolution. M., 1991).

What are the specific processes that can cause the transformation of types of ontogeny? In my opinion, this is a special kind of mutations that lead to changes in the temporal parameters of the maturation of interacting systems in development. In essence, ontogeny is a chain of embryonic inductions, those inductor-competent tissue interactions. Full-fledged embryonic induction depends on how accurately the time of maturation of the inductor and the competent tissue corresponds in development. Under normal conditions, the competent system is able to respond with shaping at the moment of the stimulating impulse from the inductor. Mismatches in the time of maturation of the inductor and the competent tissue disrupt the course of the corresponding morphogenetic processes. Mutations that cause such mismatches are probably quite widespread.

Thus, the formation of pigmentation in amphibians is determined by the interaction of the epidermis (inductor) and neural crest tissue, which serves as a source of melanoblasts migrating subepidermally under the influence of the inductor. One of the mutations (d) in the homozygote (dd) sharply weakens the color of the axolotl, so that only the back of the animal is slightly colored (the so-called white race of axolotl). It has been shown in our laboratory that the absence of coloration is determined by the mismatch in the maturation time of two interacting anlages that make up a single correlation system. In a series of experiments on transplantation of pieces of the presumptive epidermis (from which certain organs develop) between white axolotl embryos, we found that pigmentation develops in the transplant at certain combinations of donor and recipient ages.

As demonstrated by Schmalhausen and Belyaev, a typical case of such disintegration of interacting systems is domestication. For example, in the coloration of domestic animals, there is an incorrect distribution of spots of various colors (in cows, dogs, cats, guinea pigs), which does not happen in wild animals (they have either a uniform color or a regular distribution of stripes or spots). And although the genetic control of a monochromatic gray color is quite complicated, its mechanism is easily destroyed. Mutations that appear during domestication operate at the level of correlations. At the same time, significant connections are often lost, and completely new ones appear instead. The development of the crest and feathers on the legs in chickens, as well as the fat tail in sheep, are due to really new connections. Schmalhausen considers the reduction of organs as the disintegration of interacting systems, and atavism as a local reintegration, which are based on shifts in time of shaping reactions.

Macromutations according to Vorontsov. A - hairless mutants of deer hamsters (preserved vibrissae and folds of keratinized epithelium are visible); Normally, individuals of this species are covered with ordinary fur. B, a young, normally pigmented hamster homozygous for the hairless mutation. C – a young hairless albino hamster (homozygous for two recessive – hairless, albino – unlinked traits). D - hairlessness as a systematic feature in the Ceylon babirusa.

What are the possible phenogenetic bases of morphogenesis due to changes in the temporal parameters of the maturation of interacting tissues? Suppose there are two genes A1 and A2 (allelic and non-allelic, for this case it does not matter), which control the corresponding morphogenetic reactions (a1 and a2) through the synthesis of specific substances a1 and a2. Obviously, the transcription of a given locus does not yet mean that the trait controlled by it will be expressed in the phenotype. There are numerous genetic elements that can suppress the expression of a trait.
Let us assume that a morphogenetic reaction controlled by the A2 gene does not enter the phenotype due to a block at some level of regulation, for example, inhibition of the synthesis of substance a2 or a mismatch between the times of its synthesis and the maturation of the reacting system. Then only the morphogenetic process a11 is possible. If, as a result of mutation, in one of the modifier genes (M) the time of the synthesis of the a2 substance and the maturation of the reacting system coincided, and, consequently, the phenotypic expression of the trait controlled by the A2 gene, the a22 event also occurs. If reactions a1 and a2 interact, additional, intermediate shaping processes are possible. Since the relative expression of each of these responses in the phenotype will be influenced by numerous modifier genes, the number of phenotypic variants that result is almost limitless. It should also be taken into account that the M gene controls the synthesis of a particular hormone in a developing organism, and hence the overall hormonal balance. And it plays an important role in the regulation of features, including temporal, phenotypic expression of a whole complex of various traits and morphogenetic reactions. Apparently, it is these transformations that are carried out in the course of the morphogenetic process, which is disturbed by macromutation.

What causes genes to change expression time? It is possible that the heterochromatic regions of chromosomes play an important role here (they can make up from 20 to 80% of the genome). The phenotypic effect of heterochromatin often manifests itself in early embryogenesis, for example, a decrease in the number of cells per organ or the preservation of fetal characteristics after birth. It is heterochromatin and, first of all, its constituent satellite DNA that is credited with the function of the regulator of the rate of cell division and, consequently, the temporal parameters of individual development.

Heterochromatin and satellite DNA possibly affect the timing of gene expression in a twofold way: they can be associated with a certain class of proteins that can change the structure of chromatin or affect the three-dimensional organization of the interphase nucleus. In the example of pigmentation disorders in axolotls, the times of maturation of interacting tissues are probably due to the loss of a piece of heterochromatin in the region of the nucleolar organizer. Thus, in Drosophila littoralis, laboratory lines were obtained that differ in the presence (or absence) of a heterochromatin block in the G4 region of chromosome 2, adjacent to the cluster of genes that encode esterase isoenzymes. It turned out that the heterochromatin block shifts the time of expression of esterase isoenzymes in various organs of Drosophila during ontogeny.

Genetic regulation of pigmentogenesis in axolotls. (A) control embryos of white line axolotls at stages 39–40. There are no pigment cells on their lateral surface. B – results of transplantation of the presumptive epidermis from embryos of the white line at stages 34–35 to embryos of the same line at developmental stages 25–26. Embryos are fixed at stages 40–41. Pigmentation developed at the graft site (shown by arrows).

Particularly interesting are the cases when the heterochromatic block is located near the G5 region of chromosome 2 of D.littoralis. There are genes encoding three isoenzymes of b-esterase, including esterase that breaks down juvenile hormone (JH-esterase). In this case, individuals homozygous for the heterochromatic block die at the pupal stage. Then not only the time for the synthesis of JUG-esterase isoenzymes is delayed, but also the growth of their activity characteristic of normal development is inhibited. It is likely that the low activity of JH-esterase causes an imbalance in the ratio of the molting hormone ecdysone/juvenile hormone, and the established hormonal status of the developing Drosophila prevents the completion of metamorphosis.

I.Yu. Raushenbakh put forward a hypothesis (1990) according to which this organ- and tissue-specific isoenzyme, together with neuroendocrine organs, constitutes an integral system that regulates the adaptive response of Drosophila. As a result of selection, complexes of modifier genes are selected that control the expression of JH-esterase at critical moments in the development of individuals, contributing to the preservation or destruction of the existing genotypes under certain environmental conditions. In accordance with these ideas, fluctuations in the activity of JH-esterase are part of the reaction of the system responsible for the regulation of ontogeny. Sudden and deep hereditary rearrangements in the operation of such systems can produce "promising freaks" with an evolutionary future. Thus, the redistribution of heterochromatin causes a functional reorganization of the genome as a whole, sometimes affecting only individual traits, and sometimes quite profoundly transforming the phenotypic formation of trait systems.

In this regard, the organization of the karyotype in different species of Drosophila of the virilis group, which differ in the amount of heterochromatin in the genome and partly in its distribution, is of particular interest. This group includes at least 12 species, united according to the degree of morphological, biochemical similarity, as well as interbreeding. The different groups clearly differ in the amount of satellite DNA collected predominantly in the heterochromatic regions of the chromosomes.

Thus, in D. virilis, the amount of satellite DNA is almost 50% of the genome. In the texana group (D.texana, D.americana, D.novamexicana, D.lummei), the amount of heterochromatin is significantly less than in D.virilis, and in the littoralis and montana groups it is even more reduced.

J.Gall et al found that there are three main types of satellite DNA in D.virilis: 25% of the genome is the nucleotide sequence ACAAACT, 8% of the genome is ATAAACT and 8% is ACAAATT. Known tissue specificity in the distribution and differential replication of different fractions of satellite DNA. Its small amounts in euchromatic regions are differently distributed in different species of Drosophila of the virilis group. Stegnius showed that the amount of satellite DNA determines the species-specific three-dimensional organization of nuclear chromatin, as well as the attachment points of chromosomes to the nuclear matrix.

What causes the redistribution of heterochromatin in the course of evolution? Scientists have suggested that mobile genetic elements are responsible for such events, as if “pulling” pieces of heterochromatic DNA into different cells of the genome and causing Goldschmidt macromutations. Movable genetic elements can influence the implementation of hereditary information in development in at least two ways. First, penetrating into the region of a structural gene, they change the transcription rate and, accordingly, the concentration of the protein they encode by several times. Thus, in the laboratory of the American geneticist K. Lowry, it was shown that the introduction of a mobile genetic element into the alcohol dehydrogenase gene zone reduces the activity of the enzyme by about four times. If in such a situation there is a gene encoding a factor that forms a polar gradient, this will affect the development of the embryo. Secondly, mobile genetic elements are able to change the time of gene expression, which affects the interaction of tissues in development and, accordingly, morphogenetic processes.

Hypothetical scheme of macromutation (M) affecting morphogenetic processes. The a1 product is encoded by the A1 gene and determines the implementation of the a1 morphogenetic reaction, the a2 product is encoded by the A2 gene and takes part only under the influence of the modifier gene (M). In this case, it determines the realization of the morphogenetic reaction a22. The interaction of products provides variations in the morphogenetic events controlled by each of them (Korochkin, 1999).

In other words, the elimination, insertion, and redistribution of satellite DNA blocks occurring at certain points in the genome, due to their “capture” by mobile genetic elements, can be a mechanism for realizing the direction of the evolutionary process (the places of these insertions are arranged in a regular manner, and not randomly scattered throughout the genome). This kind of movement, apparently, contributes to the "explosions" of inversions and translocations, which, as a rule, accompany speciation. The works of M.B. Evgeniev clearly demonstrated the correlation in the location of satellite DNA and mobile genetic elements in various Drosophila species of the virilis group, which indirectly confirms this hypothesis.

Tissue-specific distribution of satellite DNA fractions in various organs of Drosophila virilis (Endow and Gall, 1975).

The scheme proposed by Dover for the intragenomic migration of a DNA sequence from the original chromosome 1 to homologous and non-homologous chromosomes (2, X, Y). The letters (a, b, c, d) indicate the migration paths of moving elements. The center of reproduction of mobile elements of chromosomes is indicated by blue dots. Drosophila, which has many mobile elements, is able to infect other individuals (in the figure on the right).

As the English geneticist G. Dover showed, massive displacements of genetic elements associated with a sharp increase in their number per genome can be a molecular genetic mechanism of jump speciation. The modern paleontologist J. Valentine (1975) attaches great importance in the origin of species-forming "explosions" to mobile genetic elements. And yet, evolutionary ideas based on data from developmental genetics are still only hypotheses, and paleontologists still have the final say.

The main provisions of STE: 1. The material for evolution is, as a rule, small discrete changes in heredity - mutations.2. Mutational process, population waves - factors-suppliers of material for selection - are random and undirected.3. The only directing factor of evolution is natural selection, based on the preservation and accumulation of random and small mutations.4. The smallest evolutionary unit is a population, not an individual, hence the special attention to the study of a population as an elementary structural unit of a species.

5. Evolution is divergent in nature, i.e. one taxon may become the ancestor of several daughter taxa, but each species has a single ancestral species, a single ancestral population.

6. Evolution is gradual and long lasting. Speciation as a stage of the evolutionary process is a successive change of one temporary population by a succession of subsequent temporary populations.

7. A species consists of many subordinate morphologically, biochemically, ecologically, genetically distinct, but reproductively non-isolated units - subspecies and populations. However, many species with limited ranges are known, within which it is not possible to divide the species into independent subspecies, and relict species may consist of a single population. The fate of such species, as a rule, is short-lived.

8. The exchange of alleles, the "flow of genes" is possible only within the species. If a mutation has a positive selective value within the range of a species, then it can spread throughout all its populations and subspecies. Hence the definition of a species as a genetically integral and closed system.

9. Since the main criterion of a species is its reproductive isolation, this criterion is not applicable to forms without a sexual process (a huge number of prokaryotes, lower eukaryotes).

10. Macroevolution, or evolution at a level above the species, proceeds only through microevolution. There are no patterns of macroevolution that are different from microevolutionary ones.

11. Proceeding from all the above provisions, it is clear that evolution is unpredictable and has a character that is not directed towards some final goal. In other words, evolution is not finalistic.

101.microevolution- this is the distribution in the population of small changes in allele frequencies over several generations; evolutionary changes at the intraspecific level. Such changes occur due to the following processes: mutations, natural selection, artificial selection, gene transfer and gene drift. These changes lead to divergence of populations within a species, and, ultimately, to speciation.

macroevolution of the organic world is the process of the formation of large systematic units: from species - new genera, from genera - new families, etc. Macroevolution is based on the same driving forces as microevolution is based on: heredity, variability, natural selection and reproductive isolation . Just like microevolution, macroevolution has a divergent character. The concept of macroevolution has been interpreted many times, but a final and unambiguous understanding has not been achieved. According to one of the versions, macroevolution is systemic changes, respectively, they do not require huge periods of time.

Evolutionary events can be considered on different time scales. On this basis, two sides of the evolutionary process are distinguished: micro- and macroevolution. The theory of microevolution studies the mechanisms of adaptation of populations to changing conditions of existence and the patterns of formation of new species, the theory of macroevolution studies the ways of forming larger taxa (genera, families, orders, etc.).

Macroevolutionary events - for example, the emergence of vertebrates on land - occur over hundreds of thousands or millions of years and are accompanied by significant changes in the appearance of an animal or plant. Microevolutionary events - for example, the adaptation of a rodent population to new pesticides - often require only a few years. Each macroevolutionary result consists of many microevolutionary events, the main factor of directed evolutionary changes both in micro- and macroevolutionary scales is natural selection.

A population is the smallest of the groups of individuals capable of evolutionary development, which is why it is called elementary unit of evolution. A single organism cannot be a unit of evolution. Evolution occurs only in a group of individuals. Since selection is based on phenotypes, the individuals of a given group must differ from each other, i.e., the group must be of different quality. Different phenotypes under the same conditions can be provided by different genotypes. The genotype of each particular organism remains unchanged throughout life. Due to the large number of individuals, the population is a continuous stream of generations and, due to mutational variability, a heterogeneous (heterogeneous) mixture of different genotypes. The totality of genotypes of all individuals of a population - the gene pool - is the basis of microevolutionary processes in nature.

A species as an integral system cannot be taken as a unit of evolution, since species usually break up into their constituent parts - populations. That is why the role of the elementary evolutionary unit belongs to the population.

The evolutionary process unit must meet the following requirements:

Really exist in nature;

· have a number sufficient for procreation in specific conditions;

· be relatively isolated and have a certain independence in space.

Neither the individual nor the family meet these requirements, since changes in individual individuals do not lead to any evolutionary events. An individual organism is mortal and represents only one biological generation. And even the individual hereditary traits of each particular individual may not appear in subsequent generations (due to the interaction of genes). It follows that the individual is only an object of natural selection. And the unit of evolution over generations is a certain group of individuals.

A species cannot be such a group. Individuals of almost any species in space are not evenly distributed, but in the form of clusters or islands. These clusters and islets are represented by populations. Hence, the view is discrete (discontinuous) and divisible.

An individual change that has arisen can become a group, evolutionary one only on the condition that the changed individuals must be in a community of individuals of the same species, which is sufficiently numerous and exists for a long time. Such a community is a population. It is the population that is the smallest of the groups capable of independent evolution.

Each population is characterized by distinctive features: geographically and climatically homogeneous range, age and sex composition, and, most importantly, its own unique gene pool. In different populations, gene pools differ in the set and quantitative ratio of alleles due to the unequal direction of natural selection. Persistent, occurring over several generations, changes in the gene pool of a population in the same direction are called an elementary evolutionary phenomenon. Factors that contribute to a change in the gene pool of a population are called elementary evolutionary factors, or preconditions for evolution.

102. The human population a group of people occupying the same territory and marrying freely.

In anthropogenetics, a population is a group of people occupying a common territory and freely marrying. Isolating barriers that prevent the conclusion of marriage unions often have a pronounced social character (for example, religion). Size, birth and death rates, age composition, economic status, lifestyle are demographic indicators of human populations. Genetically, they are characterized by gene pools. Of great importance in determining the structure of marriages is the size of the group.
Populations of 1500-4000 people are called dems,
DEM (from the Greek demos - people, population), a local population, small (up to several tens of specimens), relatively isolated from other similar intraspecific groupings, which is characterized by an increased degree of panmixia compared to the population. Unlike a population, a dem is a relatively short-term (several generations) grouping of individuals. Separate demes of one population may differ from each other in some morphophysiological features. The genetic concept of a deme largely corresponds to the ecological concept of a parcel.
Populations of up to 1500 people are isolates.
Relatively low natural population growth is typical for demes and isolates - about 20% and no more than 25% per generation, respectively. Due to the frequency of intra-group marriages, members of isolates that have existed for 4 generations or more are no less than second cousins. At present, migration of the population has intensified due to the growth in the number of people, the improvement of means of transport, and the uneven development of the economy.
Population waves - periodic fluctuations in the number of people in vast or limited territories, changes in population density (increases coincide with the most important achievements of mankind, decline - plague, disease, war). The nature of isolation barriers between human populations is varied. Specific to human society are forms of isolation, depending on the diversity of cultures, economic structures, religious and moral and ethical attitudes.
The isolation factor influenced the gene pools of human populations. Demos are populations of approximately 1500-4000 people. Isolates are the smallest populations - no more than 1500 people. The demes and isolates are characterized by the following features: a low (1-2) percentage of persons originating from different anthropological groups, a high frequency of intra-group marriages (80-90%) and a slight increase in population - about 20% over 25 years. In isolates, the frequency of intragroup marriages can reach 90% or more. In such an isolate, if it exists for at least 4 generations (about 100 years), all members are at least second cousins.

Currently, the following processes are taking place in human populations: 1) destruction of mating isolates; 2) environmental homogenization, which reduces the primary causes of racial differences; 3) replacement of some forms of diseases by others (for some time now, the first place has been occupied by two diseases of “civilization” - cardiovascular and oncological diseases instead of infectious and alimentary ones. These processes together lead to a numerical increase in populations. mutation process- an evolutionary factor that retains its significance in human society. Its action is similar to that of other organisms in terms of the average mutation rate, genetic and physiological characteristics, and the presence of anti-mutation barriers. At the initial stages of evolution, the characteristics of spontaneous mutagenesis were formed under the influence of various types of radiation, temperature, and a certain chemical environment. At present, the pressure of the mutation process on the gene pool of mankind is increasing as a result of the action of induced mutations, which are due to the production activity of man in the conditions of the scientific and technological revolution. Mutations occur in both sex and somatic cells. Induced mutations, as a rule, lead to hereditary pathology (generative mutations) or to an increase in the frequency of various diseases, primarily malignant tumors (somatic mutations).
Population waves (waves of life) have played a significant role in the development of mankind in the relatively recent past. The population growth rate has changed unevenly. The increase in the rate of population growth coincides with the achievements of mankind - the development of agriculture, industrialization. There is an uneven distribution of people on the planet. Against the background of a general trend towards an increase in the number of people, there were decreases in this indicator. During the epidemics of cholera and plague, only a few hundred years ago, the population of Europe decreased tenfold. Such a reduction could be the basis for a series of random undirected processes of changing the gene pool of the population of individual regions.
Insulation, as an evolutionary factor, in the past has been of significant importance. The nature of isolation barriers between human populations is social. Specific to human society are forms of isolation that depend on the diversity of cultures,
economic structures, religious and moral and ethical attitudes. Separation of people for social, religious reasons leads to the formation of endogenous groups in large cities. Jews have been kept apart for many centuries, in their genetic structure they differ from their fellow countrymen of other nationalities. recessive genes (Tay-Sachs disease, Tay-

Gaucher) are found predominantly in Jews, while the phenylketonuria gene is rare in representatives of this nationality. The high degree of isolation of small human populations over many generations created the conditions for genetic drift.

Genetic-automatic processes, or genetic drift, lead to the appearance of random, non-selective differences between isolates. An example of genetic drift is the ancestor effect. It occurs when several families create a new population, which contributes to the random fixation of some alleles in its gene pool and the loss of others. For example, members of the Pennsylvania Amish sect descended from three married couples who immigrated to America. In this isolate, 55 cases of dwarfism with polydactylism were registered, while isolated cases are described in world practice. Probably, among the founders there was a carrier of the recessive mutant allele of dwarfism - the ancestor of the corresponding phenotype. With the development of means of mass movement of people on the planet, there are less and less genetically isolated groups of the population. Violation of isolation barriers is of great importance for the enrichment of the gene pool of populations. In the future, these processes will inevitably become more and more important.
Natural selection in nature in the process of speciation transforms random individual variability into biologically useful population, species. The change of biological factors of development by social ones has led to the fact that selection has lost the function of speciation in human populations. It would, however, be wrong to completely deny the existence of selection in human society. It acts mainly during intrauterine development, plays a significant role in such forms as failed pregnancy, spontaneous abortion, stillbirth, infant mortality, sterility, and performs a well-known stabilizing role. In favor of the action of the stabilizing form of selection is evidenced by the high mortality among premature and postterm newborns compared with full-term ones. The direction of selection depends on the overall viability. Negative selection can be illustrated by the example of the Rhesus blood system. In an Rh-negative maternal phenotype, an Rh-positive fetus is always heterozygous. This means that with the death of an individual, an equal number of dominant and recessive alleles are removed from the gene pool. Selection is directed against heterozygotes. Negative selection acts in most human populations for alleles of abnormal hemoglobins, it is directed against homozygotes. In this case, alleles of one species are eliminated. Negative selection against homozygotes is overridden by strong positive selection of heterozygotes due to their high viability in tropical malaria foci.