Testing Adaptive Hypotheses of Plio-Pleistocene Hominin Craniofacial Evolution

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This project addresses the evolutionary divergence of major groups of extinct hominins from one another, with a particular focus on morphological changes associated with diet and cognition. The results will advance knowledge about evolutionary processes, shedding light on how diet-driven natural selection can interact with existing patterns of morphological integration to produce evolutionary change. The project will support a female Investigator and expand scientific infrastructure. It will also generate opportunities for training in 3D scanning, feeding biomechanics and evolutionary modeling for a postdoctoral researcher and an undergraduate student from an underrepresented group, thus broadening participation in science. The investigators will use the NSF-supported CREATE approach to produce an undergraduate teaching module using the results of this project. The research will also result in the collection and archiving of many 3D surface models and biomechanical measurements to be used by other researchers and students.The proposed research will test hypotheses about the role of natural selection in hominin evolution, including that: 1) selection for processing hard or tough foods drove skull evolution in australopiths, a group of early human ancestors, and 2) selection for complex cognition led to large brains (and thus neurocrania) in early members of our own genus, Homo. The researchers will take advantage of existing quantitative genetics tests that can distinguish between natural selection and neutral evolutionary processes using morphological data that are informative about chewing biomechanics and brain size. The researchers will measure 3D models generated from surface scans of fossils from three major groups of Plio-Pleistocene hominins: Paranthropus, Australopithecus and early Homo. In addition, measurements from extant species will be used to model population patterns of trait variation and covariation as proxies for the extinct species. The extent of trait variation and covariation are key parameters influencing the ability of a population to respond to natural selection, as well as the manner in which populations change due to random processes like genetic drift. Innovative aspects of the research include the use of biomechanically informative variables to test hypotheses about selection and assessment of how sensitive tests are to choice of living proxy for the fossils.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.