Stand and Be Counted: The Neo-Darwinian Synthesis and the Ascension of Bipedalism as an Essential Hominid Synapomorphy

Since its inception in the early- to middle-nineteenth century, human origins studies have been informed by a variety of disciplines beyond physical anthropology and archaeology, most notably geology and biology. This study examines dramatic changes within human origins research that occurred in the mid-twentieth century largely as a consequence of the dissemination of the neo-Darwinian synthesis from biology (sensu lato) into the "new" physical anthropology. This paradigm shift resulted in foregrounding evolution as a process affecting variable populations over exercises in typological classification. It led to the acknowledgement of bipedalism as the earliest hominid' adaptation, preceding other important changes in morphology (e.g. increased encephalization quotient) and behavior (e.g. stone tool manufacture and use). An important corollary of the recognition of a bipedal ape phase in our ancestry was the decoupling of the grade category "human" from the phylogenetic term "hominid."