Doctoral Dissertation Research: Form and function of the hip joint and pelvis in relationship to walking biomechanics and implications for the evolution of bipedalism

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Walking on two legs – also known as bipedalism – is a hallmark of the human lineage. It remains unclear whether and how the types of bipedalism in humans’ earliest ancestors differed from that in modern humans. This doctoral dissertation research uses 3D motion analysis to investigate how variation in the appearance of the lower limb skeleton is related to biomechanical performance while walking on two legs. In addition to direct observation, this project also experimentally tests the effects of hominin skeletal anatomy on bipedal performance. This transformational approach aims to produce a validated methodological framework for future research into the diversity of locomotor behavior in hominins. The project's anticipated outcomes include a large dataset of interest and use to anthropologists, clinical and functional anatomists, physical therapists, and other clinicians, and a new, open-source tool for measuring skeletal features that can be used by anthropologists, morphologists, and clinicians. This project supports the work of an early career scientist from a group underrepresented in STEM and provides training opportunities for undergraduates in biological anthropology, anatomy, radiology, 3D motion analysis, and more.While Australopithecus and early Homo are widely agreed to have been habitual bipeds, the form of bipedality in different hominin species and the timing of emergence of a human-like striding bipedal gait remain a subject of debate. Pelvic morphology and torsion in the lower limb bones vary among hominin taxa, and because this variation is associated with variation in the biomechanics of bipedalism in living humans, there is a unique opportunity to test hypothesized gait differences in Australopithecus and early Homo compared to later hominins. This doctoral dissertation research uses a combination of ultra-low dose standing biplanar radiographs and 3D motion analysis in a sample of living humans to quantify variation in pelvic and lower limb skeletal torsion and determine the effects of skeletal torsion across the lower limb on locomotor performance in vivo. This study integrates a novel method for measuring skeletal morphology of living subjects in 3D with established approaches to motion analysis to explore fundamental questions in functional morphology and human evolution. These findings can better characterize the functional significance of skeletal variation and its implications for understanding the diversity of locomotor behavior in hominins, as well as provide a lens through which to interpret the role of locomotion in hominin evolution, which are argued to be critical to the evolution of the genus Homo.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.