Doctoral Dissertation Research: Functional signals of upper limb use in the collarbone

One of the defining milestones in human evolutionary history is the transition to walking on two legs – bipedalism – although it is difficult to reconstruct the degree to which fossil species might have simultaneously still been active in the trees. This doctoral dissertation research project analyzes the distribution of different types of bone in the collarbone of several species who get around in different ways, to better reconstruct and understand the use of upper limbs in fossil human relatives. Shifting to a predominantly bipedal mode of locomotion is associated with several other key developments in human history, including stone tool production and use, long range hunting and associated meat preparation and consumption. Gaps have remained in approaches and have impeded the refinement of ways to identify the transition away from use of upper limbs in locomotion in human evolution; the results of this research contribute to the reconstruction of patterns of locomotion during human evolution with greater resolution. This project provides training relevant to both STEM education and clinical practice for underserved students. This project quantifies different aspects of the morphology of the primate clavicle, and the results contribute to longstanding key debates regarding upper limb use in early hominins. This study quantifies and compares variation in external clavicular shape, and the distribution of cortical and trabecular bone in the primate clavicle, throughout ontogeny and across groups with diverse locomotor adaptation. It further models how morphological variation affects the loading of the clavicle during locomotion, and finally applies these results to building context to document and interpret variation the early hominin fossil record with respect to assessing locomotor adaptation. This study further enhances the ability of researchers in biological anthropology and related fields to glean information about the degree of arboreal behavior in fossil hominins, ultimately allowing a clearer understanding of the associations between anatomy and ecology. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.