Doctoral Dissertation Research: Ontogeny, Evolution, and Ecogeographic Patterns of Human Limb Morphology

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Modern humans expanded into nearly every region of the world, adapting both culturally and biologically to a range of natural environments. Past research in human skeletal biology has shown that the human limb skeleton shifts toward a shorter, more robust morphology in cold-adapted populations and a taller, less robust morphology in heat-adapted populations. This doctoral dissertation project will examine how evolutionary processes have shaped this diversity in the human limb skeleton through changes in growth and development (ontogeny). The project will directly address the relationship between different evolutionary forces and changes in growth trajectories, advancing knowledge about biological mechanisms underpinning human morphological adaptations and plasticity. Reconstructed 3D surface renderings from computed tomography (CT) scans and other data generated from this project will be shared freely to facilitate further research and the development of online teaching materials. In addition, the project will promote undergraduate mentoring and training, as well as national and international collaborations through conferences, seminars and workshops with partner institutions.Past studies have shown that adaptation by natural selection to climatic conditions, neutral (non-selective) evolution, and non-heritable change in response to climatic conditions (phenotypic plasticity) may all play important roles in shaping the diverse morphological patterns observed in the human limb skeleton. In addition, studies on juvenile skeletons have shown that these morphological patterns are evident at young ages. When and how these different evolutionary forces influence limb shape and size during growth remain unclear. This project uses a global sample of osteometric measurements taken from bone specimens of archaeological populations and 3D modules reconstructed from CT scans of contemporary population to tease apart these different evolutionary forces. The investigator will use a range of statistical methods and models to address whether: 1) selection on body size during growth will have different effects on limb morphology, 2) neutral evolutionary forces can account for some of the divergence in growth trajectories in addition to climatic adaptation, and 3) selection acts primarily on adults, juvenile individuals, or both.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.