The search for an understanding of "human nature" leads back in time to a consideration of the processes which shaped our physical, social, emotional, and cognitive characteristics. In order to trace the conditions under which humanity arose and eventually came to flourish, it is necessary to reconstruct the divergence from ape forebears some 5 million or so years ago. Many explanations of our origins have been proposed. Some can be summarized by evolutionary slogans such as "the killer ape," "the naked ape," "men in groups," or "man the hunter," which emphasize competition, aggression, sex, meat eating, and hunting. Hunting in particular has been the basis for interpreting early human fossils.