Masticatory Biomechanics and the Primate Face

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The research proposed here entails the initial phase of a comprehensive analysis of primate masticatory biomechanics. The primary goals are (1) to determine how patterns of facial bone strain are influenced by major biomechanical variables (skeletal geometry, material properties, and external forces), and (2) to test hypotheses purporting to explain the pattern of similarities and differences in facial strain observed among living primates. Several types of primary data will be collected that are fundamental to a complete understanding of primate feeding mechanics. These data include (1) in vivo and in vitro bone strain, (2) electromyography, physiological cross-sectional area and muscle fiber orientation of the muscles of mastication, (3) three-dimensional information about craniofacial geometry, and (4) material properties of craniofacial bones and sutures. Functional hypotheses will be tested by integrating these data using finite element analysis, a widely used engineering technique designed to examine how objects of complex geometry deform under load. The initial phase of this research has two components. The first component will entail the modification of a finite element model of the craniofacial skeleton of Macaca to incorporate new data (muscle and bone properties, EMG, and in vitro and in vivo bone strain) to develop a model approach to the study of primate craniofacial structure and function. This phase will enable the researchers to demonstrate the viability of the proposed methods, their ability to integrate vast amounts of diverse types of data, and the significance of the various types of data for understanding adaptions related to the functional morphology of the craniofacial apparatus. The second component will include preliminary analysis of the significance of structural and functional differences between anthropoids and strepsirrhines through initial studies of Eulemur fulvus and Cebus capucinus. Following analysis of the results of this initial project, the investigators will apply for funds to expand the sample sizes and/or the taxonomic scope of the study, as indicated by our findings.This research will have a broad social impact. It will: (a) provide the broadest examination yet of facial biomechanics; such basic science research will find applications in clinical sciences related to the craniofacial development, growth, pathology, and trauma, (b) using FE models, limit the need for, or at least increase the analytical power of, future experimental studies requiring the use of live animals, (c) demonstrate the inherent interdisciplinarity of physical anthropology, (d) provide an example of how complex systems can be analyzed using a combination of empirical data and computational modeling, (e) strengthen collaborations between anthropologists in five universities, and (f) provide funding to graduate students at three universities.