BIOTIC INTERACTIONS IN THE CONTEXT OF HUMAN EVOLUTION: THE FOSSIL RECORD OF LARGE MAMMALS

The eastern African fossil record has produced rich vertebrate faunas, including human ancestors, going back to the late Miocene. Most of the literature on rates and timing of speciation and extinction in this context has focused on climate, and especially global climate, as a primary driver of evolution. We analyzed sampling-standardized diversity dynamics of fossil eastern African bovids (antelopes) and large mammals from the Turkana Basin. We found almost no peaks in turnover rates that coincided with specific global climate change events. Long-term changes in faunal composition support the influence of continental environmental change (aridification) at the million-year time scale. However, continuous turnover, stable species richness, constant species durations, and symmetrical occupancy curves all suggest that evolution at the 100 kyr scale was strongly modulated by biotic interactions (e.g. food webs). Early human evolution occurred within this faunal context and was probably also driven more by biotic interactions than commonly considered.