Tooth chipping can reveal bite forces and diets of fossil hominins
Paul Constantino, James J. Lee, H Chai, Bernhard Zipfel, Charles Ziscovici, Brian R. Lawn, Peter Lucas
Fossil hominin tooth enamel often exhibits antemortem edge chipping (Robinson 1954; Tobias 1967; Wallace 1973). Here we apply a simple fracture nist-equation to estimate peak bite forces from the sizes of such chips. This nist-equation, previously validated by chipping tests on glasses and fine-grain ceramics (Chai & Lawn 2007a), is confirmed by analogous tests on extracted modern human teeth. Bite forces calculated for hominins and selected living species accord with estimates from empirical jaw mechanics. Our results show that the forces required to form mm-scale chips on the posterior teeth of fossil hominins (and orangutans and peccaries) often exceed 1 kN, depending to some extent on tooth size. The presence of such large chips supports the consumption of large hard foods like seeds (or mollusc shell or bone) (Strait et al., 2009). Apart from providing quantitative estimates of bite forces, analysis of chip signatures greatly expands our knowledge of diet from use-wear analysis. In particular, it suggests a way of detecting the fallback consumption of hard foods that methods like low-force dental microwear and isotopic analysis tend to miss.