Michael Sockol: UC Davis Department of Anthropology

The origin of the human family, Hominidae, has been a primary focus of paleoanthropologists for more than a century. Indeed, the desire to understand our origins is ubiquitous in human society. Of continuing interest to anthropologists is the nature of the shift to bipedal locomotion in our earliest hominid ancestors. Though debate exists about whether bipedalism serves to define Hominidae, it is clear that becoming bipedal was the critical first step in the emergence of the human form, preceding all other major morphological adaptations. Yet, while the end result is apparent in the fossil record, the process by which bipedalism arose is unclear. Numerous hypotheses have been proposed for the shift to bipedal locomotion. Many have been discarded while others have withstood the test of time. One such hypothesis, commonly referred to as the “energetics hypothesis”, posits an energy savings associated with bipedalism in an ecological context. I review the current state of our knowledge of the shift to bipedal locomotion in early hominids and give reasons for considering the energetics hypothesis as crucial to understanding that shift.