1Anthropology, New York University, 2Anthropology, Hunter College, 3New York Consortium of Evolutionary Primatology, (NYCEP)
Friday 8:45-9:00, Ballroom C
Occlusal surface area varies among fossil hominins, and this variation is thought to reflect chewing performance; however, there is morphological equifinality when enlarging an occlusal surface; for example, both increasing slope (sharpness) and two-dimensional area of the post-canine teeth would increase the total occlusal surface. In order to explore this variation in modern humans, we quantified occlusal surface morphology and tested its relation to chewing efficiency. Occlusal surfaces were measured using the program ArcGIS from three-dimensionally scanned dental casts of each subject’s upper and lower right dental rows, third premolar to terminal molar. Slope, two and three-dimensional area, and volume were recorded for each subject and used to calculate morphological indices. Each subject participated in a series of almond chewing trials which were recorded using high speed motion capture and surface electromyography of the masseter muscle. From these trials, chewing efficiency was calculated from the change in particle size relative to mechanical work of the masseter. Chewing efficiency was significantly higher in individuals with smaller occlusal areas (both two-dimensional and three-dimensional areas) and volumes. However, chewing efficiency increased in individuals with greater occlusal slopes. For almonds and foods with similar mechanical properties, these results indicate that highly sloped but small dentitions are more efficient in modern humans. We discuss the implications of these results when estimating chewing efficiency in occlusally diverse hominins including Australopithecus and Paranthropus.
Funding was generously provided by NYCEP, Hunter College, and NYU.