Eighteen detailed FE models of enamel microstructure were created and analysed. The results highlight the uniqueness of A. anamensis dental structure and imply that mastication in this species included a greater shear component than in Pan, as well as a wider range of loading directions; it is similar to that in Gorilla in this respect. These findings are in accord with microwear studies (Grine et al., 2006a). Unlike either of the great apes, however, enamel microstructure of A. anamensis was found to be poorly equipped to withstand loading parallel to the dentino-enamel junction; such loading regimes are associated with mastication of soft fleshy fruits. This, together with broader morphological considerations, raises doubts as to whether A. anamensis was essentially a frugivore that expanded its dietary niche as a result of fluctuations in environmental conditions, e.g., during seasonal food shortages. Instead, it is more parsimonious to conclude that the habitual diet of A. anamensis differed considerably from that of either of the extant African great apes.