Human cold adaptation: an unfinished agenda.

1975 marked the end of a 20-year period of human biology research on physical environment. The focus then shifted from climatic adaptation to problems of nutrition, disease, and stress. However, many questions about human environmental patterns, especially in reference to their evolution, were abandoned rather than resolved. Assumptions about cold protective functions of low surface area/body mass ratio are entrenched in physical anthropology, despite lack of experimental validation. Since heat loss is controlled by vasoregulation and tissue insulation, a simple physics model of SA:mass may not apply. The issue merits investigation, as do the assumed thermal advantages of foreshortened extremities. Physiological assessment remains our primary research tool. In cold climate natives, elevated basal metabolic rates now appear to be genetically induced. During cold exposure, the body manages heat conservation through well known channels but also by specialized thermogenic functions such as metabolism in brown adipose tissue (BAT). The powerful protective capacity of BAT is largely unexplored either within or between populations of cold exposed human adults. An irony of our profession is that many biological variables seem to have minor effects when compared to behavioral cold protections. This is partly because biological anthropologists may have made incorrect assumptions about what most threatens the well being of cold climate people. Contrasts in environmental behaviors when comparing northern cultures such as Inuit, Athabaskan, and Norse are particularly instructive. Adaptations to life in the cold may ultimately reveal their secrets through biocultural research design modeling of environmental research. With both practical and theoretical gains still wide open, the field needs renewed attention from human biology.