The origin of hominid bipedalism re‐examined

The evolution of habitual terrestrial bipedalism in the ancestor of the Hominidae can be reconstructed through an examination of historical transformations of shared‐derived morphological‐behavioural complexes related to bipedalism in catarrhines. This reconstruction indicates that terrestrial bipedal displays may be of particular importance in understanding the development of habitual terrestrial bipedalism because they are the most recently acquired morphological‐behavioural characteristic shared by the African great apes and humans. We suggest that in the late Middle and Late Miocene of East Africa, as habitats were becoming more open and desiccated and resources more widely separately, increased competition for resources ensued. We propose that the adoption of bipedal displays were the behaviours essential to the success of pre‐hominids in this environment in that they allowed for the relatively peaceful resolution of, firstly, intragroup and, eventually, intergroup conflicts. It is hypothesized that the widespread use of bipedal displays for social control in pre‐hominids reduced a major source of morbidity and mortality. Bipedal postures, once adopted for social control, probably became common elements of the pre‐hominid postural repertoire. With time, this new pre‐adaptation to upright standing would have facilitated a multifactorial development of fully habitual terrestrial bipedal locomotion.