Macrowear and biomechanical analyses of great ape molars

Luca Fiorenza, Stefano Benazzi

Research output: Contribution to conferenceAbstract

Abstract

Dietary diversity in primates is reflected in their dental morphology, with differences in size and shape of teeth . This is particularly noticeable if we look at great ape lower molars. For example, while orangutan molars are characterized by a low and blunted cusps morphology with a highly crenulated surface and thick enamel layer, gorilla thin enamel molars show a high relief with sharp cusps joined by long shearing crests. This dental morphological difference seems to be an adaptation for the intake of completely different foods: hard and brittle in orangutans, and pliant and tough in gorillas . In this study, we want to investigate if molar morphology of Pongo pygmaeus, Gorilla gorilla and Pan troglodytes is biomechanically adapted to resist certain types of foods. We employ a com- pletely new digital approach that combines dental macrowear studies with Finite Element Analysis using high-resolution models generated from micro-computed tomography. Our preliminary results on lower second molar (M2) show significantly different wear patterns between these three species. Pongo pygmaues displays a flat occlusal surface characterized by similar proportions of chewing phase areas (Buccal Phase I, Lingual Phase I and Phase II). In contrast, macrowear of Gorilla gorilla is dominated by steep facets and highly developed Lingual Phase I and Phase II areas, with small Buccal Phase I facets. Pan troglodytes occlusal wear is intermediate between the ones of gorilla and orangutan. Tensile stress in Pongo pygmaues is low, probably because the occlusal sur- face is horizontally loaded with a chewing surface almost compressed. In contrast, because of the high cusps of gorilla molars, the pressure on cusps causes high tensile stress along the tooth grooves. Pan troglodytes is characterized by the largest loaded area and therefore, the pressure (and compression stress) on its enamels is the smallest. Molar macrowear results are strongly linked to dietary diversity found in great apes, with a homogeneous flat occlusal surface typical of a diet consisting of hard foods, and a steep pattern dominated by Lingual and Phase II areas typical of a diet rich on tough vegetable foods. Our biomechanical analysis suggests that while molars of gorillas are better suited for shearing, the tooth morphology of orangutans is more adapted for crushing. This new approach can be further used to advance our understanding of the diet, morphology and evolution of extinct hominins.
Original languageEnglish
Publication statusPublished - 2017

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