HUMAN BIOLOGICAL ADAPTABILITY

Adaptation is an aspect of virtually all questions of human biology. Besides their interest in evolution through adaptive selection of the primates, including man, physical anthropologists are concerned with biological adaptability as a human attribute. In this sense adaptation has been examined at three overlapping levels: (i) those represented by differences in the extent of inherent capacities in subpopulations long exposed to different conditions, such as differences in the inherited determinants of body form and skin pigment in peoples in different climatic zones; (ii) adaptations acquired during the growth period of the individual such as residual stunting and reduced caloric needs in individuals receiving low caloric diets throughout childhood; and (iii) reversible acclimatization to the immediate conditions such as the changes which make it easier to work at high altitudes after the first few days there. Greater resilience to change is achieved if adaptations are reversible in each generation or within a lifetime. This implies an evolutionary tendency to shift human adaptability from genetic selection to ontogenetic plasticity to reversible adaptability.