Doctoral Dissertation Research: Ecology, biology, and coexistence among multiple species of human ancestors

Variation in the human fossil record from sites in eastern Africa is too great to be attributed to one hominin species. It has been suggested that up to five hominin species – Paranthropus boisei, Homo habilis, Homo rudolfensis, Homo ergaster, and Homo erectus ¬– overlapped in space, time and in the dietary resources consumed. This project identifies the extent and type of competition between eastern African P. boisei and early Homo during the Pleistocene (after c. 2.5 mya). Understanding how early Homo responded to competition with other species at this critical early stage in the history of our genus allows us to better appreciate our own anatomy, behavior and plasticity. This study also has broader implications for ecological and biological research. Character displacement, which is one of the factors that enables the coexistence of closely related species, influences the structure of ecological communities, and helps drive speciation and the distribution of biodiversity. The project also creates lesson plans with education experts in the United States and internationally and supports the training of a woman scholar. The researchers use 3D geometric morphometric (GM) shape-change analysis to test whether interspecific competition influenced the evolution of our genus Homo through time, and whether there were any significant morphological effects of this competition. Conventional wisdom suggested that early Homo led to the extinction of P. boisei over time through competitive exclusion. However, this project applies an updated 3D GM shape-change analysis methodology to test for ecological niche incumbency, a type of competition hypothesis that has not typically been considered in paleoanthropology. The investigators use molar morphological evidence from over a million years in P. boisei and early Homo to investigate the nature and potential causes of any interspecific competition. The results of this study may provide evidence of competition between these genera through time and transform previous narratives of Homo exceptionalism by showing how a non-ancestral hominin may have influenced the trajectory of our own ancestral lineage. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.