the first member of the genus homo to be hairless was "homo erectus", originating about 1.6 million years ago. the dissipation of body heat remains the most widely accepted evolutionary explanation for the loss of body hair in early members of the genus "homo". the reduction in hair, and the increase in sweat glands, made it easier for their bodies to cool. man's ancestors moved from living in shady forest to open savanna. this change in environment resulted in a change in diet, from largely vegetarian to hunting. hunting game on the savanna also increased the need for the regulation of body heat.