Concepts and methods of ecological anthropology. Bio-cultural adaptations-Genetic and non Genetic factors. Mans physiological responses to environmental stresses: hot desert, cold, high altitude climate.
Concept of ecological Anthropology:
It integrates the fact regarding human physiology,geography,genetics,society and culture in order to throw invaluable light on the way in which human species try to maintain equilibrium with the environment by adopting to it. Ecological anthropology tries to explore the multilevel ways in which human adjust to their surrounding by both biological and non biological processes.
It concentrates on the mechanism of human adaptability. It is unique in its way because it integrates the finding from ecology physiology social and cultural anthropology and geography around the set of problems set or posed by the human habitats.
Methods of ecological anthropology:
the research strategy of ecological anthropology is to study a wide range of human responses to environmental problems, to social constraints, and to past solutions of environmental problems. Little and Morren have succinctly expressed the strategy as ecological anthropologists are concerned with those cultural and biological responses,factors,processes and cycles that affect or are directly connected with the survival, reproduction, development, longevity or spatial positions of people.
Bio-cultural adaptation: genetic and non genetic factors.
Different genetic variation is expressed in biochemical ,physiological,immunogenetical,and other aspects of functions. Changes in these features along with behavioral changes ensured by cultural components are crucial for human survival. Human adaptability therefore, includes both a biological component and a cultural component.
Human adjustment occur in the following way:
Adjustment→biological and cultural.
Biological→acclimatizations(whole genetic system) and adaptations(one or few genes)
In Biological adjustments, there are changes in the structural and physiological system of organism whereas in cultural adjustments human populations use methods and practices learnt from its ancestors over long period of time for its survival. Changes in height pigmentation facial feature etc in response to a particular physical environment is biological adjustment whereas use of certain diet ,dress,activity pattern rituals etc. are cultural adjustments.
Biological adjustments can be acclimatizations and adaptations.
Acclimatizations are changes in physiological processes in response to changed environment. It is always temporary changes and species wise i.e. if individuals revert to original environment the changes vanish. Ex-acclimatization for high altitude,heat stress. Entire human species react similarly in such conditions. acclimatization involve whole genetic system and not a single or few genes.
Adaptations, on the other hand is a permanent change structure and physiology of an organism. Different populations of a species may be adapted differently to live in its environment. An eskimo has small limbs to prevent loss of heat whereas has normal trunk length so that maximum metabolic energy is generated. Also they have cold genes which keep their limbs warm and save them from frost bite. Adaptation occur in cold climates and at high altitude and also for food and against diseases. A variety of cultural adaptation has also occurred in response to diet and disease.
Sometimes it is difficult to classify an adjustment as acclimatization or genetic adaptation for ex- level of melanin in skin can adjust to the gene of dark and light skin people.
Man’s physiological responses to environmental stresses:
Hot desert:Adaptations to Heat:
Human species developed in tropical savannah type climate hence we are quite capable of tolerating moderate heat and a temperature of 30 degree c +- 5 degree c is well tolerated. Problems arise when temperature gets above 35 degree c. heat load is first lessened by radiation and then, if core temperature does not come down,hypothalmus of brain is activated for sweating. Sweating takes away a lot of heat as heat of evaporation. If the heat load continues for some days. There is developed heat acclimatization.
1. Heat is tolerated first by thermal gradient:this occurs due to radiation of heat from body to surrounding air.
2.heat adaptation by sweating in low vapour pressure area:when heat is not tolerated by thermal gradient our sweat glands become active and sweating occurs. Human skin is covered by 1.5 million sweat glands.
3.heat adaptation by thermal gradient only in high vapour pressure area:the smaller body weight generates less metabolic heat and larger surface area dissipates it because In smaller individual the ratio of surface area to body weight is higher. In moist humid hot climate there is no heat loss by sweating. The only means being the thermal gradient and heat loss through the skin. The surface area thus increases in such cases along with increase in length of the extremites such as limbs and ear mainly seen in nilotics of africa.
4.Heat acclimatization is the final stage of heat tolerance:if the individuals from different climate mainly cold works in the cold for 10 days the difference between the local and cold people disappears, because heat acclimatization is a universal human capability.
5.culture and heat:humans have well found ways to resist the heat from the vest past and adopted to use against its day to day variations.
Adaptations to Cold:
Man, because of its savannah origin, is a poor tolerant of cold and rely more on cultural adaptations than biological adaptations.
Our adaptation against cold chiefly consists of narrowing down the blood vessels of the extremities of the body,including skin whenever we are faced with a cold spell. When blood vessels are narrowed down there is less flow of blood to the extremities and consequently, less heat loss.
Population adaptation is marked in both whole body and extremity cooling.
Population differences in whole body cooling: africans are best adapted against whole body cooling. They maintain higher temperature during freezing condition. Europeans are the second aborigines and inuits are the worst and their body temperature falls much lower thus threatened by frostbite.
Population differences in extremity cooling:in a comparison between native african,european, americans,indians,artic americans indians,and inuits. The relative level of extremity cooling was highest in native african followed by europeans,americans,indians,artic indians and inuits. A native african maintains the lowest cooling characterized by lowest rewarming tendencies.
→Acclimatization has some role to play:man because of its tropical origin shows poor acclimatization against cold stress. It has been found in north atlantic fisherman that cold exposure for many years may enhance their response to cold adaptations.
→cultural material and behavioral adjustment are more important:the nature od clothing,the way of constriction of shelters and use of fire are definitely most important.
→cultural adaptation has influenced genetic adaptations:this is evident from clothing patterns of inuits. They have unique clothing which warms the body core but leaves the extremity cold. The heated body core supplies heat to the extremities and they are kept warm.
Adaptation to high altitude:
Since atmospheric pressure drops at high altitude there is shortage of oxygen to tissues and biological adjustments tend to correct this shortage. It involves both acclimatization and adaptation.
1.increased breathing rate:hypoxic condition stimulate appropriate nervous centres to cause instant increase in breathing rate to 65%.
2.increased rbc and haemoglobin:hypoxic conditions stimulate kidneys to secrete erythropoietin that increses rbc count and haemoglobin level from 15gm/dl to 22 gm/dl.
3.increased lung surface:it means more oxygen could diffuse to the blood.
4.cellular acclimatization:hypoxic conditions cause increase in mitochondria and some other cellular enzyme systems. oxygen inhaled is ultimately used by mitochondia for energy.
5.increased tissue blood supply:
6.shift of oxygen-dissociation curve to right:
the permanent inhabitants of high altitude show following adaptations.
1.their chest size is greatly increased giving a high ratio of ventilatory capacity to high body mass.
2.their body size is decreased to reduce the body mass.
3.size and weight of babies born tend to be smaller. High level of nutrition and care do not come in the way.
4.their heart particularly the right side of heart is greatly increased to ensure supply of larger amounts of blood to lungs for oxegenation.
5.shape of nose color skin are adaptive. nose is shortened to reduce nasal passage way, and nostrils directed upwards.
6.capacity of their hemoglobin to extract oxygen. The pressure of oxygen at which hemoglobin is saturated is very low in high landers.