The problem of human adaptation is

The problem of human adaptation isThe problem of human adaptation is complex in its essence, and therefore is studied by many specialists (doctors, physiologists, anthropologists, demographers, economists and others) at various levels of biosystem organization  - population, individual, cellular, molecular and submolecular. Primary attention in these complex studies is given to regions with extreme conditions of existence, where selection was most intensive, as well as to the most important socio-economic processes that lead to the formation of artificial ecosystems (industrialization and urbanization).

For constitutional anthropology, the morpho-functional aspects of adaptation are of the greatest interest. Currently, 500 different ethno-territorial groups of Eurasia, Africa, America and Australia are studied and described, including 60 populations in the territory of the former USSR.

The formation and preservation of morphological polymorphism of different human populations is explained by the fact that in the early stages of its evolution, humanity was more directly exposed to biotic and abiotic environmental factors than it is now. Complexes of such factors had a multidirectional effect on human populations. As a result, various adaptive types of people were formed in different climatic and geographical zones.

The adaptive type is the norm of the biological response to a complex of environmental conditions and is manifested in the development of morpho-functional, biochemical, and immunological features that ensure optimal adaptation to these living conditions.

The complex features of adaptive types from different geographic zones include General (non-specific) и Specific items. The former include, for example, indicators of osteomuscular body mass, the amount of immune proteins in human serum, the concentration of adrenal hormones in the blood. Such elements increase the general body resistance to the action of adverse environmental factors.

Specific elements are diverse and are closely related to the prevailing conditions in a given habitat — hypoxia, a hot or cold climate, and so on. It is their combination that serves as the basis for the selection of adaptive types: tropical, arctic, temperate zones, alpine, arid and others.

Let us consider the main factors acting on human populations in various climatic and geographical zones, and the corresponding adaptive types formed under their influence.

<H2> Arctic adaptive typeH2>

Arctic adaptive type formed in areas located above 66 ° 33? north latitude. The indigenous population of the Far North, belongs to the Mongoloid race and is mainly represented by reindeer herders, fur farmers, and hunters. Habitat conditions in the Arctic are characterized by low air temperature, strong winds, and poor vegetation. Due to the low temperature in the air, water and soil, there are few microorganisms, cyst pathogenic protozoa, eggs and helminth larvae. Of the nutritional factors, the main are the primary use of animal products rich in proteins and fats. Plant food is available to the inhabitants of the Arctic only for a short summer, in small quantities.

The arctic populations are characterized by a mesomorphic type of constitution: a strong development of the musculoskeletal component of the body, a large chest volume, and a long massive body. The representatives of the Arctic adaptive type of limb are short, which, in combination with a large body, gives them a short, athletic (“stocky”) look, people with asthenic physique are almost not found among the northern nations.

This body type has the largest ratio of body weight to body surface area (P / S index), that is, with a large “core” of the body, where heat is produced, they have the smallest “shell” of the body, from the surface of which heat transfer occurs to the surrounding environment by evaporation of sweat, convection and radiation. Such a structure allows a person to better keep warm and avoid hypothermia, but only this mechanism in cold conditions would not be enough. A high level of heat production is also required.

The formation of heat in the body occurs in the process of the breakdown of nutritional products (proteins, fats and carbohydrates), and the subsequent synthesis of its own structures. At the same time, part of the energy released as a result of oxidation due to the phosphorylation of ADP is bound in the form of an ATP macroergic bond, and some in the form of primary heat goes into the tissue and provides for their warming. ATP energy is then wasted by the body to perform all vital functions - the synthesis of plastic substances, secretion and excretion, the conduct of nerve impulses, muscle contraction, and so on. Since the energy efficiency of ATP is never equal to 100%, part of the released energy goes into the tissue as secondary heat and also contributes to the body's warming.

From all the above, it can be seen that increasing the formation of heat and warming the body in cold climates is possible due to:

1) increase the basal metabolic rate, that is, increase the intensity of metabolism;

2) an increase in the formation of primary heat as a result of the separation of the processes of oxidation and phosphorylation;

3) increase the generation of secondary heat. The most significant in this regard is contractile thermogenesis - increased muscle tone, muscle tremors, and an increase in voluntary muscle activity. This, apparently, led to a significant severity of the muscular component in the structure of the body of the inhabitants of the North.

Increasing the basic metabolism requires a high calorie diet, so in cold conditions, the use in food of animal proteins and fats rich in energy is a necessity. However, for the assimilation of such food requires the restructuring of enzyme systems. In this regard, the Arctic adaptive type is characterized by an increased ability to oxidize fats. Of the biochemical parameters associated with the level of basal metabolism and nutrition, it is necessary to note the high content in the blood of the total amount of protein, cholesterol and gamma globulins.

Basal metabolism is regulated mainly by thyroid hormones thyroxin and triiodothyronine, therefore, in the Arctic adaptive type, the amount of these hormones in the blood is also increased.

<H2> Tropical adaptive typeH2>

Tropical adaptive typebeing the most ancient and original for humans by origin, it was formed over vast territories, which are very diverse in climatic and geographical conditions. Since the terrain and position above sea level near the equator vary greatly, a tropical type has formed among residents of tropical rain forests, shrouds, light forests and arid plateaus. The ecological specificity and diversity of the racial composition of the inhabitants of the tropical and subtropical belts (Caucasians, Mongoloids and Negroids) determined the morphological diversity of representatives of the tropical adaptive type.

The tropics are characterized by the following adverse factors: high air temperature, strong solar radiation, high air humidity, the prevalence of plant foods in the diet and the lack of animal protein. The soil, air and water contain a large number of microorganisms, helminth eggs and protozoa. The richness and diversity of the animal world ensures the existence of a huge number of intermediate and final owners of helminths and vectors of infectious diseases.

Of these factors, the main factor determining the development of members of any race of the constitutional type of the tropical type is the high heat load. In general, for the tropical type are characteristic:

First, the prevalence of body height in length over height in height, long limbs and, as a result, low P / S and P / L indices (the ratio of body weight and surface area, weight and body length). Absolute body sizes vary greatly among different nationalities, depending on many factors, especially on the nature of food (many researchers consider, for example, the microsomal type in pygmies as an option to adapt to the lack of animal protein in the diet), but the described body proportions are found in most tropical inhabitants (elongated body type is found in about 70% of Negroids). Such a morphotype has a relatively large “shell” of the body with a small “core”, which provides more efficient heat transfer.

Secondly, the inhabitants of the tropics formed a special pattern of perspiration, contributing to better cooling of the body due to evaporation of moisture from the surface of the body. Compared with other adaptive types, they have a greater amount of sweat glands per unit area of ​​the skin, the secretory activity of the sebaceous glands is stronger, therefore sweat is formed in a large amount, is evenly distributed on the skin and is held on it for a long time, and does not roll down from the skin in the form of drops, like the Europeans.

The third characteristic feature of the tropical type, independent of the race of the people, is a strong pigmentation of the skin. It is due to the high intensity of solar radiation, especially the ultraviolet spectrum. Pigmentation of the skin reduces the carcinogenic and mutagenic effects of sunlight. Proved that among the indigenous population of Africa and Australia, skin cancer is much less common than among Caucasians.

The fourth feature of the inhabitants of the tropics is associated with the predominance in the diet of vegetable carbohydrate foods, as well as the lack of need for high-energy endogenous compounds. This resulted in a decrease in blood cholesterol levels in Tropics, as well as in lipolytic enzyme activity.

The unfavorable epidemiological situation has led to the formation of a fifth distinctive feature in representatives of the tropical adaptive type - intense immunity, which is manifested in an increased level of immunoglobulins in the blood, in the greater activity of white blood cells. The wide spread of malaria in some populations has led to the fixation of a specific mutation of the gene responsible for the synthesis of hemoglobin S. Erythrocytes with such hemoglobin turned out to be more resistant to the introduction of the malarial plasmodium, which facilitates the course of this disease.

<H2> Arid adaptive typeH2>

Arid adaptive type formed among the inhabitants of the desert. For the desert, the main harmful factor is exposure to dry air, which has a large evaporative capacity. In addition, in tropical deserts there is a year-round strong thermal effect, and in the extratropical zone there are sharp seasonal temperature drops — heat in summer and cold in winter. Under these conditions, as well as in the tropics, long-bodied morphotypes are more common (up to 70%), the muscular and fatty components develop poorly, but the total body size of the inhabitants of the deserts is larger. The level of basal metabolic rate is low, the amount of cholesterol in the blood is reduced.

High mountain adaptive type is the youngest by origin, this is evidenced by the fact that after moving to lowland areas, the highlanders in the next generation did not observe adaptive changes typical for high mountains.

Regardless of the climatic zone, the main adverse factor in the mountains is a small amount of oxygen in the air - hypoxia. In addition, there is the influence of low temperatures and the relative monotony of food.

The adaptation complex formed during hypoxia consists of morphological and functional changes that facilitate the entry of oxygen into the body. These include: increasing the volume of the lungs (and, accordingly, the chest), increasing the oxygen capacity of the blood by increasing the number of red blood cells (increasing their formation in the bone marrow), increasing the concentration of hemoglobin in them, and facilitating the binding of oxygen to hemoglobin in the lungs. In order to increase the supply of oxygen through ineffective gas exchange in the lungs, the heart increases the volumetric blood flow through the lungs. This work is done against the background of a significant increase in blood viscosity due to an increase in the number of red blood cells in it. The result of this overload of the heart muscle is its hypertrophy.

Exposure to cold in the mountains leads to an increase in thyroid function, an increase in the level of basal metabolism and the amount of heat produced, but in many highland areas the opposite is observed due to iodine deficiency in water and food. At the same time, the disease can develop - endemic, that is, characteristic for this area, goiter, one of the manifestations of which in its innate form is cretinism.

<H2> Adaptive type of temperate climate zoneH2>

Adaptive type of temperate climate zone in its pure form at the present time can be observed only in people living in rural areas or in small towns. Most of the inhabitants of temperate latitudes are currently concentrated in cities, where anthropogenic factors rather than climatic factors are in the first place.

Morphological and functional indicators, as well as the degree of their variability, in this adaptive type are “intermediate” between tropical and arctic types. This is facilitated by the absence of extreme factors, seasonality of the climate, as well as migration.

Urban Adaptive Type currently not fully formed, the poet can only talk about trends in its formation. The main adverse factors of large cities include pollution of the habitat, the greenhouse effect, a sedentary lifestyle, high population density and the associated stresses and epidemiological distress. Therefore, for an urban adaptive type, the following are considered characteristic: an increased prevalence in the population of extreme morphotype variants, an increase in fat deposition, a greater manifestation of acceleration manifestations, and a significant lability of mental reactions.

In conclusion of the conversation about the adaptive types of the constitution, it should be noted that their formation took place and takes place in parallel, against the background of racial genesis and independently of it. The evolutionary relationships of different adaptive types among themselves and with the main races can be depicted as a diagram.