Genetics with the Fundamentals of Breeding - M.P. Myhun - 2008

Chapter VII. Human Genetics (Anthropogenetics)

7.1. The Biological Essence of Man

Anthropogenetics is both a fundamental and applied science that studies heredity and Variability in the most complex Representatives of the living world - human beings. The research findings in this field are important not only from a theoretical perspective but also hold significant practical value.

In biological systematics, humans belong to the species Homo sapiens. Human growth, development, and reproduction are governed by the same laws that apply to all species of animals, plants, and microorganisms. Indeed, A number of phenotypic traits, such as hazel-grey eyes, curly-straight Hair, free-attached earlobes, thick-thin Lips, long-short eyelashes, large-small eye size, etc., are inherited According to the monohybrid scheme; whereas if parental organisms are heterozygous for two or more qualitative genes, the respective traits in their offspring form according to the polyhybrid scheme. Similarly, Quantitative Traits such as linear, volumetric, and weight dimensions of organisms, The amount of Hormones secreted by Endocrine glands, human intelligence levels, and others are characterized by polygenic inheritance.

The human genotype and karyotype, like those of all other Organism species, are characterized in their function by mutational, combinative, and modificational variability. Sex, as in other dioecious species of animals and plants, is controlled by the genotypes of X-Y Chromosomes. Humans are characterized by immense trait variability, and a selectivity of marriages is inherent to them.

The General structural plan of chromosomes, their Functions in mitosis, Meiosis, Crossing-over processes, mutagenesis, DNA Synthesis, etc., are subject to ordinary cytogenetic laws.

The scientific facts cited above convincingly demonstrate the biological essence of man as a distinct taxonomic species. However, in The process of evolutionary development, humans separated from the animal world, achieving the highest degree of development in the organic world. This occurred thanks to labor activity aimed at shaping living conditions. The search for tools and work Methods stimulated the evolution of intelligence toward human mental activity. Since survival under those complex conditions was only possible through collective work, humans formed as social beings through their labor activity.

The Study of taxonomic species of plants and animals shows that in nature they are represented by certain groups of individuals distinguished by their characteristic lifestyle or behavioral features. Such groups have been named biotypes. It turned out that the biotypes of each species inhabiting different natural and climatic zones genetically adapt to respective environmental conditions. Groups of organisms of the same species or subspecies that share common traits while acquiring minor differences among themselves under METABOLISM/18.html">The Influence of various environmental conditions are called races. The species Homo sapiens also subdivides into races. Human races are large historically formed groups of people united by a common origin and The Structure of certain minor hereditary physical characteristics (body structure, Skin, eye, and hair color, HEAD shape, height, etc.); however, the Main Features of the human phenotypic Organization (skeletal, muscular, and Brain structure) are identical in people of all races. Representatives of each race are characterized by common phenotypic traits acquired under the influence of natural and social conditions of existence. Practically, humankind is divided into three major races: Caucasoid (Eurasian), Mongoloid, and Equatorial (Negro-Australoid). The term "Negroid race" is sometimes used as a synonym for the latter.

Based on the phenotypic peculiarities of external features inherent to representatives of a certain race, French sociologist and writer J.A. de Gobineau put forward the first racist concept in the mid-19th century. He became one of the founders of the ideology of racism and the racial-anthropological school in sociology. Subsequently, Gobineau's ideas were further developed in Western European countries, giving rise to racist theories.

However, scientific research has shown that all human races share a monophyletic origin and that there are no sharp genetic differences between them that could be regarded as species differences; consequently, all of humankind represents a single biological species. The fact that the elementary unit of the hereditary substance in hominids is the Gene indicates a vast genotypic variability of traits in humans, since in its function each gene is characterized by a specific mutation frequency. In every generation, it passes through the crucible of genetic recombination, and during organism development, its morphogenetic activity is modified by environmental conditions. This genotypic and phenotypic variability is so great that differences in the expression of the trait system are viewed at the level of individual humans rather than races. However, individual variability does not preclude the evaluation of mean values of adaptive traits. When the difference between the mean values of a measured trait is statistically significant, one can speak of the given populations belonging to different races. Yet, the traits by which a person can be assigned to a particular race are very few, whereas hereditary traits equally inherent to people of all races are countless. This testifies to the belonging of people of all races to the same species.

The latter assertion is also convincingly proven by the fact that marriages between representatives of different races are always characterized by high cross-fertility of partners and high viability and fertility of their offspring. At the same time, the traits of individual crossability and the viability and fertility of their offspring serve as the primary criterion for the genetic unity or genetic dissociation of traits used to determine whether these individuals should be classified into the same or different species.

In the first half of the 1930s, Russian geneticist M.P. Dubinin established that outwardly normal, highly viable Drosophila individuals living in nature carry three to four lethal and several non-lethal recessive genes in their genotypes. The former in a homozygous state cause a lethal outcome, while the latter reduce the viability of individuals that have inherited the corresponding genes. This phenomenon was termed the genetic load.

It turned out to be present in the genotypes of all diploid species of organisms, and thus in the human genotype as well. Of course, Mutations are the sole source of all forms of mutational, combinative, and modificational variability, without which species evolution could not take place. Mutagenic variability in species populations also leads to the birth of genetically abnormal offspring, represented by disabled individuals and those with distorted phenotypic traits, and in humans, mentally abnormal individuals as well. All of these mutations in humans constitute the genetic load of their genotypes, which accounts for about 4% of births of hereditarily defective children and 25% of abortive zygotes out of the total number of conceptions. Along with this, humans possess a multitude of mutations that create vast trait variability but do not affect viability, and therefore are not classified as part of the genetic load. These include, in particular, Gene Mutations determining hair and eye color, free or attached earlobes, positive or negative reaction to the taste of phenylthiocarbamide solution, Blood type, etc.

In modern conditions, The Effect of natural Selection on humans is weakening; all healthy members of society have the opportunity to leave descendants in the next generation. Individuals of plant or animal species in the wild are deprived of such an opportunity, since under the pressure of natural selection not all of them prove capable of reproducing offspring. As a consequence, the genetic potential of the respective species narrows.

In humans, conversely, the participation of all healthy individuals in reproduction (amid significant population growth) substantially broadens the genetic potential of mankind. Thanks to this, in each new generation, the collective level of spiritual and intellectual features grows due to an increase in the number of genetically diverse individuals and rare genotypes of outstanding persons.

The emergence and enrichment of the social program in humans is typically accompanied by a weakening of natural selection, and for a number of traits, its complete cessation; however, natural selection remains a factor stabilizing the biological organization of Homo sapiens even today. Suffice it to recall early zygote resorption, which accounts for 25% of all conceptions. A striking example of the stabilizing action of natural selection in humans is the significantly increased survival rate of children whose body weight approaches statistical mean values.

The second major genetic process occurring in human populations is racial admixture. Since ancient times, human migration has facilitated the incorporation into the collective human gene pool of all mutant genes that arose in isolated populations, resulting in its massive polymorphism.

The disruption of isolation barriers caused by migration is of immense importance for enriching and improving the gene pool of mankind. The heterosis effect will inevitably manifest itself. This is already being confirmed today. Indeed, against the backdrop of improving living conditions and the occurrence of mixed marriages resulting from The breakdown of isolates, the genotypes of many human populations have become healthier.

In 1869, English psychologist and anthropologist F. Galton proposed studying influences that could improve the hereditary qualities (health, mental abilities, giftedness) of future generations, expressing the view that through encouragement and restrictions in partner pairing, human biological qualities could be improved. He first formulated THE PRINCIPLE OF eugenics (from Greek *eugenes* - well-born) - the science of human hereditary health and Ways to improve it. This science became a branch of Human Genetics, the subject of which is Genetic Methods for improving hereditary traits, especially combating Hereditary diseases. Some geneticists, like Galton, believed that As a result of the mutation process under conditions of weakened natural selection, biological degeneration of humans takes place. Since factors such as drug Treatment of infectious diseases, Sanitary and hygienic measures, improving living conditions, etc., not only weaken but also halt natural selection, individuals with defective, mutant genes survive and reproduce, introducing them into human population genotypes, which leads to their degeneration.

However, the dynamics of processes occurring in populations show that genetically ill individuals, even if they participate in reproduction, always produce fewer offspring than their healthy relatives. Therefore, the concentration of each defective allele will change so slowly that its effect will manifest only after thousands of generations.

Erroneous views on the causes of human degeneration led to the Conclusion that due to the propagation of defective genes and their random distribution among individuals, groups of organisms with fully functional or defective genotypes are formed. Opinions were also expressed that the gene pool of humankind, as a historically young species, contains many animal genes that devalue the biological nature of man.

In the opinion of some eugenicists, human nature can be "refined" if all mutant and other inefficient genes are removed from its gene pool. Such ideas were often used to justify racism.

A new wave of speculation regarding the "refinement" of human biological nature swept through science in the 1960s. In particular, American geneticists H. Muller and C. Davies put forward the idea of placing human reproductive processes under Genetic control. At the same time, Muller proposed not only periodically applying series of Inbreeding and artificial selection in human populations, but also mass Artificial Insemination using sperm from "outstanding" men.

Many prominent geneticists (including J. Haldane, Th. Dobzhansky, B. Wallace, D. McKay, M.P. Dubinin, and others) spoke out against such eugenic propaganda. Dobzhansky and Wallace stated that the Implementation of such a program would be madness, and its consequences could be no less dangerous than exposure to ionizing radiation. Scientific analysis showed that if the ideas of H. Muller and C. Davies were implemented, genetic diversity would sharply decline. This would ultimately reduce the adaptive capabilities of the human gene pool. Selection breeding would produce populations of standard humans. It goes without saying that a society composed of standard humans cannot exist. It would lose The ability to produce necessary means for its own life support, losing the intellectual, psychological, and physical diversity of individual humans without which society cannot develop.

Human intellectual, psychological, and other traits are polygenically inherited. This means that, in terms of their biological properties, the genotypes of individuals from different social strata are entirely identical. The overall gene pool of any nation's population consists of a vast array of genes which, through recombination, form the genetic potential of that country, and on a global scale, the genetic potential of all humanity.

For instance, following the Bolshevik October Revolution, over 3 million people fled Russia, the vast majority of whom represented the intellectual wealth of the former empire. Wars claimed the lives of millions of physically healthy individuals, while millions more intellectually developed, hardworking members of Soviet society were repressed in peacetime, with many executed. The country lost a tremendous share of its intellectual potential. Yet, within two to three decades, this potential was restored through new generations who propelled the former USSR to a global level in science and the arts, thereby refuting eugenicist theories regarding the necessity of "improving" human nature.

A crucial question remains unanswered by eugenicists: whether attempting to "improve" human nature might destroy the unique human genetic program. After all, none of them yet know according to which criteria such an improvement should be made. Meanwhile, reckless Interference in the human gene pool can cause irreparable damage to the hereditary structures of future human populations.

Only one thing is indisputable: we must treat hereditary diseases, of which around 3,000 are currently known. Medical genetics is dedicated to developing diagnostic and treatment methods for such conditions.