ABSTRACT
Bipedality freed the mouth and teeth, which enabled hominids to develop a more complex call system, the prerequisite of language. These developments required larger brains. The energy cost of the human brain eventually reached three times the level for chimpanzees, accounting for up to one-sixth of the total basal metabolic rate. Higher encephalization was critical for the rise of social complexity, which raised the survival odds and set hominids apart from other mammals. Foraging hominids could secure meat on grasslands and woodlands even without any weapons, either as scavengers or as unmatched runners. Average foraging densities ranged from just around one person to several hundred people per hundred square kilometers. The absence of a typical foraging pattern does not preclude the recognition of a number of biophysical imperatives governing energy flows and determining the behavior of gathering and hunting groups.
