Dietary Properties and Chewing Patterns in Primates: An Analysis of Cyclical Loading

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

This project investigates relationships between diet and chewing behaviors in primates, to improve our understanding of the evolution and variation in primate and hominin feeding behaviors. The investigators will measure chewing patterns in 23 primate species that are given foods spanning a range of material properties, to see how individuals in each species process the different foods and how this processing relates to the shape of their jaw and skull. These comparative data will be important not only for framing ecological research in living primate species, but for reconstructing diet and feeding behaviors in extinct primate and hominin species based on fossil jaws and skulls. The project will foster interdisciplinary approaches to training and education involving members of under-represented groups, and will support training and mentorship of a postdoctoral fellow, graduate students and undergraduates as well as local STEM teachers and students, all of whom will participate in lab apprenticeship, scientific presentations and public outreach to local institutions and the lay public. Therefore, another benefit to society includes development of a novel training environment for the next generation of academic researchers and educators. Phenotypic variation in the primate skull is influenced by masticatory stress, with taxa relying on stiff or tough foods having specialized jaws, teeth and jaw muscles. However, the link between diet and jaw form in living and fossil primates is poorly understood. Difficulty understanding adaptive diversity in the feeding apparatus is due to two shortcomings of the evidence about diet-related chewing and loading behaviors. The first is the fact that infrequent, high-magnitude forces elicit the same physiological and evolutionary responses in bone as do low-magnitude, cyclical loads. In the skull, a second and related issue is a surprisingly incomplete knowledge of the role of food properties on variation in chewing behaviors that underlie load-related variation in primate jaw form. Given the ubiquity with which cyclical loading is invoked to explain jaw robusticity in fossil hominins, the remarkable lack of key behavioral data on this chewing pattern cannot be overstated. Using in vivo data on 23 representative primate species kept in domestic institutions, this project tests the hypothesis that food material properties affect masticatory parameters underlying variation in cyclical loading of primate jaws: chewing frequency, chewing investment, and chewing duration. High-speed video will record dynamic diet-related chewing patterns in isolated and unrestrained adult primates presented a known mass of five foods that span a range of material properties paralleling the diversity of values for items ingested by wild primates. Intra- and interspecific analyses will compare chewing parameters with food stiffness, toughness, and respective oral fragmentation indices. Due to its experimental and comparative focus, this in vivo research is likely to inform theoretical and methodological advances in biological anthropology and other organismal and biomedical fields.