Natural Selection and Man's Relative Hairlessness

THE ORDER of mammals to which man belongs, the Primates, has well over 600 species, all of which are well endowed with body hair. Man's relative hairlessness (glabrousness) stands in marked contrast with the thick pelage which usually covers the bodies of all other primates, especially those of man's nearest relations, the great apes. The reduction of body hair in man almost certainly followed upon adoption of the erect posture and the new way of life which resulted from the increasing dessication of the hominid homeland—Africa south of the Sahara. Climatic changes transformed forested woodlands into open plains with low vegetation, savannas. It was not that man's progenitors abandoned the trees, but that the trees abandoned them. Life on the savannas presents very different challenges from those to which forest dwellers are accustomed. Forest dwellers are herbivorous in their diet. The savannas are not sufficiently vegetated to maintain all animals on a vegetarian diet, and all