Stress Distribution and Molar Macrowear in 'Pongo pygmaeus': A New Approach through Finite Element and Occlusal Fingerprint Analyses

Abstract

'Pongo pygmaeus' is a large great ape that lives in highly seasonal environments of Borneo, where the preferred foods, such as ripe and soft fruits, are often unavailable. During these periods orangutans rely on hard food items, such as nuts and seeds, which become particularly challenging to eat. Is their dental morphology designed to feed on these hard foods? In order to answer this question we employ an innovative digital approach that integrates Finite Element Analysis with occlusal molar macrowear. Our preliminary results on a lower second molar (M₂) suggest that the feeding behavior of orangutans manly involve crushing masticatory processes and little shearing, typical of hard-object diets. The morphology of 'P. pygmaeus' M₂, with low cusps, thick enamel and a wrinkled occlusal surface seem to minimize tensile stresses in the tooth. The protostylid with its (moderate) buttress-shaped morphology seems to functionally suffer the high tensile stresses concentrated along the buccal groove of the crown by the extensive load applied on the buccal cusps during maximum intercuspation. Thus, it appears that non-preferred foods (also called fallback foods) such as nuts and seeds have played a major role in the evolutionary and morphological adaptations in 'P. pygmaeus' molars. This new method can be further used to advance our understanding of the diet, morphology and evolution of extinct hominins.