Bite force, diet, and cranial morphology of fossil hominids

Abstract

Functional parameters that approximate the maximal adducting force of the jaw were measured on cranial samples of extant hominoids and well preserved fossil hominid skulls. Estimates of bite force based on these measurements were calculated for the hominid fossils and for extant hominoid species. Relative to known or estimated body weight, only the robust australopithecines proved capable of generating bite forces that are exceptionally high compared to those characterizing living species. Forces developed by gracile australopithecines and early Homo resemble those of chimpanzees. When bite force is plotted against the occlusal area of the molar teeth, neither robust nor gracile forms deviate substantially from the regression line based on living hominoid species. We suggest that the high bite force of the robust australopithecines was a necessary consequence of the enlargement of molar crown surface. Bite force reduction is a late trend in hominid evolution that parallels a reduction in tooth size. Some of the characteristics of early hominid skull shape can be interpreted as adaptations to augment bite force with increasing tooth size.