The thermoregulatory advantages of large body size for hominids foraging in savannah environments
Estimates are presented of the net thermal loads, and associated drinking water requirements, experienced by naked bipedal hominids weighing between 10–100 kg. The increase in body size observed in the hominid fossil record would have conferred significant advantages to these primates when foraging on dispersed resources in open equatorial environments, where drinking opportunities were limited. Larger hominids dehydrate more slowly and are able to cover a greater distance each day before encountering thermoregulatory constraints. This substantially increases the home range area, and consequently the quantity of dietary resources, to which they would have had access. The potential relevance of these thermoregulatory factors to the high degree of sexual size dimorphism in early hominids is discussed.