On the Relationships of Postcanine Tooth Size with Dietary Quality and Brain Volume in Primates: Implications for Hominin Evolution

Abstract

Brain volume and cheek-tooth size have traditionally been considered as two traits that show opposite evolutionary trends during the evolution ofHomo. As a result, differences in encephalization and molarization among hominins tend to be interpreted in paleobiological grounds, because both traits were presumably linked to the dietary quality of extinct species. Here we show that there is an essential difference between the genusHomoand the living primate species, because postcanine tooth size and brain volume are related to negative allometry in primates and show an inverse relationship inHomo. However, when size effects are removed, the negative relationship between encephalization and molarization holds only for platyrrhines and the genusHomo. In addition, there is no general trend for the relationship between postcanine tooth size and dietary quality among the living primates. If size and phylogeny effects are both removed, this relationship vanishes in many taxonomic groups. As a result, the suggestion that the presence of well-developed postcanine teeth in extinct hominins should be indicative of a poor-quality diet cannot be generalized to all extant and extinct primates.