Postcranial Dimorphism in Primates

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Understanding male and female differences (dimorphism) in body size is critical for determining the biological meaning of skeletal variation in living and extinct species. Furthermore, dimorphism provides some of the only evidence for reconstructing behavior in extinct species. Postcrania offer critical information about body size and size dimorphism in extinct species. However, given the irregular form of most postcranial bones and fragmentary nature of the fossil record, the types of data that can be gathered and analyzed have been limited. This study will employ new laser-scanning technology to capture postcranial bone form in 3-D point clouds, and develop techniques for assessing surface form using POLYWORKS analytical software. Data will be gathered for a comparative sample of 27 primates, with a focus on measuring true joint surface areas, bone-cross sectional form, and volumes. Further geometric measurements will be developed, with an emphasis on identifying male and female differences in bone curvature, joint surface orientations and topography, and the size of muscle attachment areas. Analyses will quantify patterns of sex differences within and across species, evaluate the relationship between skeletal and body size dimorphism, and develop methods for reconstructing size dimorphism from skeletal remains. Results from this project will significantly improve our ability to characterize and evaluate aspects of bone form that have been inaccessible using traditional techniques. The comparative data base will allow a more refined understanding of the evolution of size dimorphism and postcranial morphology in extinct species. The broader impacts of this research include opportunities to train students in cutting edge technology for comparative studies of skeletal form, and the development of methodologies which offer enormous potential for future biomechanical and comparative studies in primates and humans in biological and clinical fields. Finally, scanned data will be made available to other researchers, offering opportunities for further analysis and potentially reducing wear and tear on irreplaceable museum collections by permanently recording data in a non-invasive manner.