Some Problems of Human Variability and Natural Selection in Climate and Culture

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Abstract
Man has evolved to his present state by natural selection in both pre-cultural and cultural times and situations. Since the Pliocene several species and races of man have evolved and some have disappeared, at different rates. Whereas most primates occupy hot damp environments, some are adapted to dry heat and others to cold. Man inherits a physiological versatility in his capacity for climatic adaptation. For present purposes the author follows Ernst Mayr''s classification of fossil and living men into one genus, Homo, and two species, erectus and sapiens. Erectus includes half-brained and sapiens full-brained men. Slnanthropus, Neanderthal, etc. are races only. More than one fossil race of sapiens may survive in the genetic composition of modern geographical races. During the Pleistocene tool-making influenced human relations which in turn furnished a basis for natural selection physically and physiologically. Like other warm-blooded animals man varies in bulk according to Bergmann''s rule and in form according to Allen''s. Certain variations, as for example those of posture, found among living races, may reflect earlier adaptations to forest versus open country hunting. Variations in hair form and distribution may reflect early needs of both environmental and interpersonal protection and of courtship. The social life of tool-making animals placed a premium on high intelligence, fostering the selection of a large, efficient brain. Being expensive in terms of blood supply such a brain requires efficient food-gathering to permit its survival. Brain efficiency and culture had to move hand in hand. The versatility of the modern human brain could reflect the pooled capacities of several large-brained fossil races.

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