The loss of functional body hair in man: the influence of thermal environment, body form and bipedality

Abstract

An insulating layer of body hair is crucial to the thermoregulatory energetics of most mammals. Only some highly specialized aquatic forms and a few fossorial and terrestrial species which experience special heat stress problems have evolved a naked skin. Man's body size and form suggest that his naked skin is associated with the prevention of hyperthermia in hot climates rather than an aquatic ancestry. The reduced direct solar radiation exposure of hominids in open equatorial environments, resulting from their unique bipedal posture, may explain the absence of this characteristic among other savannah mammals of comparable body mass.