On the calculation of occlusal bite pressures for fossil hominins

Abstract

Reconstructing the feeding behavior of fossil hominins, and especially of australopiths, is currently the focus of several lines of work (e.g., Grine et al., 2006; Sponheimer et al., 2006, 2013; Ungar et al., 2008; Strait et al., 2009; Constantino et al., 2010; Wroe et al., 2010; Cerling et al., 2011; Henry et al., 2012; Delezene et al., 2013; Zink et al., 2014; Smith et al., 2015). One of these lines of research consists of estimating bite forces from fossil skulls based on estimates of lever arm length and cross sectional area of the masticatory muscles (e.g., Demes and Creel, 1988; Eng et al., 2013). The results of such studies can be expressed as unitless values (Demes and Creel, 1988), or as estimates of the maximal vertical (i.e., perpendicular to the occlusal plane) adducting force that could be produced by a given jaw (Demes and Creel, 1988). Although this kind of analysis does not take into account other aspects, such as the differential activity of the muscles involved in mastication, or food processing modes, the results are still related to the bite force capabilities of fossil hominins. Demes and Creel (1988) proposed the existence of a nearly linear correlation between bite force produced at themesial margin of the second upper molar (M2) and M2 area for extant hominoids and fossil hominins, although early Homo (represented by the fossil specimens OH 24 and KNM-ER 1813) and Australopithecus africanus (Less).