On the relationship between maxillary molar root shape and jaw kinematics in and .

Plio-Pleistocene hominins from South Africa remain poorly understood. Here, we focus on how and exploited and-in part-partitioned their environment. Specifically, we explore the extent to which first maxillary molar roots (M) are oriented and thus, by proxy, estimate the direction of loads habitually exerted on the chewing surface. Landmark-based shape analysis of M root reconstructions of 26 South African hominins and three East African suggest that may have been able to dissipate the widest range of laterally directed loads. and , despite having overlapping morphologies, differ in aspects of root shape/size, dento-cranial morphologies, microwear textures and C4 food consumption. Hence, while monophyly cannot be excluded, equivalence of dietary niche can. The South African hominins occupied distinct ecological niches, whereby appears uniquely adapted to dissipate antero-posteriorly directed loads.