MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

BIOLOGY

CHAPTER 2. BIOGEOCENOTIC LEVEL OF LIFE ORGANIZATION AND HUMAN PLACE IN IT

2.1. BASICS OF HUMAN ECOLOGY

Human Adaptive Ecotypes

As a result of natural factors that vary across different Regions of the planet, specific human adaptive types have formed throughout human history and continue to exist today. An adaptive type is a complex of features (morphofunctional, biochemical, immunological) that ensure optimal biological adaptation of humans to a specific physical environment. The existence of various adaptive types indicates significant human ecological plasticity, which is believed to have been one of the Prerequisites for the global dispersal of humans. Human adaptive types formed independently of race in response to specific ecological challenges based on the corresponding Gene pool. This process involved The formation of populations whose gene pools matched local conditions better than the gene pool of the species as a whole. The following human adaptive types are distinguished: arctic, tropical, temperate zone, desert, and high-altitude.

The arctic adaptive type formed as an ADAPTATION TO A humid, cold climate and oxygen deprivation. It is characterized by a relatively strong development of The Musculoskeletal System, large chest dimensions, high Hemoglobin levels, a relatively large volume occupied by Bone Marrow, an increased mineral content in bones, high Blood levels of Proteins and Cholesterol, and an enhanced capacity for fat oxidation. Arctic indigenous populations have a greater body mass than southern inhabitants. A larger mass helps retain body heat more effectively, a function also served by a layer of subcutaneous fat. In body proportions, There is a reduction in leg length relative to arm length. Overall, the arctic type is characterized by elevated METABOLISM/26.html">Energy Metabolism, which maintains stable parameters under hypothermia conditions. There are also specific thermoregulation mechanisms. For example, under the same degree of cooling, Canadian Indians experience a sharp drop in Skin Temperature while their metabolic rate changes very little, whereas incoming white populations show a lesser degree of skin temperature reduction accompanied by strong shivering, meaning metabolism is intensified.

The tropical adaptive type. Subtropical and tropical regions exhibit exceptionally high Variability among population groups. Both the shortest and tallest populations live here. Nevertheless, ecological factors, particularly climatic ones, have contributed to The Development of Specific features of the tropical adaptive type. Negroids feature an elongated body shape, reduced Muscle mass, a relative decrease in body weight coupled with an increase in limb length, a reduced chest circumference, more intense sweating due to an increased density of Sweat Glands per 1 cm² of skin, low basal metabolic and fat synthesis rates, and a reduced cholesterol concentration.

The temperate zone adaptive type occupies an intermediate position in somatic indicators between the indigenous populations of the arctic and tropical regions.

The desert adaptive type. According to UNESCO data, deserts cover about one-fifth of the total land area of the continents. Ecological factors driving the Formation of the desert human adaptive ecotype include high solar radiation intensity (shade temperatures reaching +50°C), low precipitation, and dry air. Under conditions where the body receives a large amount of heat, the primary physiological challenge is to increase heat dissipation to maintain Homeostasis. This is achieved through Water evaporation. Each gram of evaporated fluid dissipates 2.43 kJ (0.58 kcal) of heat. Indigenous peoples of Central Africa, South India, and other regions with hot and dry climates feature long, slender limbs and a small body mass, yielding a higher surface-area-to-volume ratio—and the larger the surface area, the greater the heat dissipation. To compensate for water losses caused by increased sweating, there is a need to increase fluid intake. Local populations are better adapted to these conditions, consuming less water than newcomers from the temperate zone. Under high-temperature conditions, the requirement for proteins and fats decreases because these foods have a high energy value and additionally provoke thirst. A carbohydrate-rich diet increases physical endurance.

The high-altitude adaptive type. High-altitude environments are extreme for humans in many respects. They are characterized by low atmospheric pressure, reduced partial pressure of oxygen, cold, and a relatively monotonous diet. The primary ecological factor driving the formation of this human ecotype is believed to be Hypoxia. Regardless of climatic zone, race, or ethnicity, high-altitude residents exhibit the following features: an elevated basal metabolic rate, relative elongation of the long tubular BONES OF THE Skeleton, a wide chest, and increased blood oxygen capacity due to a higher erythrocyte count, elevated hemoglobin content, and the relative ease of its conversion to oxyhemoglobin.