Extant ape dental topography and its implications for reconstructing the emergence of early Homo

Dental topography has successfully predicted the diets of species in several extant and extinct 11 mammalian clades. However, dental topographic dietary reconstructions have high success rates only 12 when closely related taxa are compared. Given the dietary breadth that exists among extant apes and 13 likely existed among fossil hominins, dental topographic values from many species and subspecies of 14 great apes are necessary for making dietary inferences about the hominin fossil record. Here, we 15 present the results of one metric of dental topography, Dirichlet normal energy (DNE), for seven groups 16 of great apes (Pongo pygmaeus pygmaeus, Pan paniscus, Pan troglodytes troglodytes and 17 schweinfurthii, Gorilla gorilla gorilla, Gorilla beringei graueri and beringei). DNE was inadequate at 18 differentiating folivores from frugivores, but was adequate at predicting which groups had more fibrous 19 diets among sympatric African apes. Character displacement analyses confirmed there is substantial 20 dental topographic and relative molar size (M1:M2 ratio; length, width, and area) divergence in sympatric 21 apes when compared to their allopatric counterparts, but character displacement is only present in 22 relative molar size when DNE is also considered. Presence of character displacement is likely due to 23 indirect competition over similar food resources. Assuming similar ecological conditions in the Plio-24 Pleistocene, the derived masticatory apparatuses of the robust australopithecines and early Homo may 25 be due to indirect competition over dietary resources between the taxa, causing dietary niche 26 partitioning. Our results imply that dental topography cannot be used to predict dietary categories in 27 fossil hominins without consideration of ecological factors such as dietary and geographic overlap. In 28 addition, our results may open new avenues for understanding the community compositions of early 29 hominins and the formation of specific ecological niches among hominin taxa.