Dental macrowear analysis in Great Apes

Chimpanzees (Pan troglodytes), orangutans (Pongo pygmaeus) and gorillas (Gorilla gorilla) rely on different food sources. This dietary diversity is reflected in their dental morphology, with different size and shape of teeth. However, while the shape of unworn teeth can suggest what a tooth is capable of processing, tooth wear can tell us how a tooth is actually used. In this study we apply the Occlusal Fingerprint Analysis (OFA) method using 3D digital models of great ape teeth, to show how wear facets are created and what jaw movements are responsible for their formation. The results show significant differences between the three groups analyzed here: in Pongo the occlusal surface is characterized by large and flat phase II facets, while in Gorilla there is a minimal development of buccal Phase I facet and a steep wear facets inclination. Pan are somehow in between, with large Lingual Phase I facets and moderately steep wear planes. These macrowear patterns can be explained with variation in diet and habitat use. In fact, while orangutans relies on hard food objects more than any other living great apes, showing thus a larger proportion of crushing wear, gorillas exhibit an increase in shearing wear which is an adaptation for their folivorous and fibrous diet. Finally, the “intermediate” tooth macowear found in chimpanzees, mirrors their highly variable diet. The OFA method demonstrates to be a powerful tool for better understanding the relationships between food properties, mastication and tooth wear processes in living primates.