1Department of Anthropology, New York University, 2NYCEP, New York Consortium in Evolutionary Primatology, 3Department of Anthropology, Hunter College, 4Department of Anthropology and the Center for Human Evolutionary Studies, Rutgers University, 5Center for the Advanced Study of Hominid Paleobiology, George Washington University
March 26, 2015 1:00, Grand Ballroom E/F/G
A reduction in the size of the dentition and masticatory complex are among the features used to define the genus Homo, and are associated with dietary changes and a reduction in food material properties. Homo and Australopithecus are therefore predicted to have differences in chewing efficiency resulting from these morphological changes, particularly of tough food items. From these predictions, we hypothesize that humans with a larger dentition and masticatory complex are more efficient than smaller subjects at processing foods with greater toughness and hardness. To test this hypothesis, 30 human subjects completed chewing trials that were recorded using high speed motion capture and surface electromyography of the superficial masseter and anterior temporalis muscles. Each subject’s dentition was cast and occlusal surface morphology was quantified using dental topographic analysis. Trial foods varied in toughness and hardness, and the material properties were measured using a FLS-1 portable universal tester. Overall, subjects were significantly less efficient when chewing foods of greater toughness and Young’s modulus. Increased occlusal surface area was significantly positively correlated with chewing efficiency for foods of greater toughness; however, variation in occlusal surface area did not significantly predict variation in chewing efficiency for foods of lower toughness. These results suggest that the decrease in dental and masticatory size in Homo was coupled with a decrease in chewing efficiency of tough foods. We discuss the implications of these results for dietary strategies in Australopithecus and for interpreting diet material properties from dental and masticatory morphology.
Funding was provided by NYCEP, Hunter College, and NYU.