1Department of Biology, Marshall University, 2Department of Human Evolution, MPI-EVA, Germany
Thursday 10:30-10:45, Grand Ballroom II
Tooth enamel is a hard substance that does not deform easily under load. However, it is also brittle and susceptible to fracture. Previous work has shown that such fractures can be used as a diagnostic tool for reconstructing bite forces in mammals with bunodont dentitions. Through simulated biting experiments on model tooth structures and extracted human molars, three principal fracture modes in enamel – radial-median cracks, margin cracks, and chipping – have been identified. Fracture mechanics theory from materials science allows one to derive explicit relations for quantifying critical bite forces from each crack type in terms of characteristic tooth size and enamel thickness. We used 2D and 3D computed tomography to determine enamel thickness and tooth size in a series of fossil hominin lower molars from both East and southern Africa, and then used these data to calculate and compare bite forces among those hominins. The results show that the “robust” australopiths were capable of very high bite forces, in the range of 2000 N, but even the more gracile australopiths had bite forces in the range of extant great apes and considerably higher than those of modern humans.
This work was supported by NSF grant number 0851351 (to PC).