Doctoral Dissertation Research: Dental function and tooth wear in the evolution of primate molar form

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Old World monkeys are the most geographically widespread and ecologically diverse group of living primates, with a wide range of diets made possible by the combination of their gut adaptations and the unique shape of their molar teeth. Old World monkeys acquired "bilophodont" molars, with cusps united into two pairs of wedges, soon after diverging from a last common ancestor with apes. This doctoral dissertation project will investigate the functional significance of this shift in molar form, drawing upon, and contributing to, a framework that considers how dental wear alters the shape and function of teeth throughout an organism's life. This project will also provide opportunities for public outreach and undergraduate research engagement, including students traditionally underrepresented in STEM careers. The large number of 3D scans generated by this project will be made publicly available through MorphoSource, where they can have further use for scientific and educational purposes. Primates, like all herbivorous mammals, face selective pressures to maintain function of their permanent teeth in the face of tooth wear. This project will use 3D dental topographic methods to measure the shearing and crushing/grinding potential of molars at varying wear stages in a sample of extant and fossil catarrhines (i.e., Old World monkeys, apes, and humans). First, the investigators will establish a baseline of how extant catarrhine molars are altered by macroscopic wear and use phylogenetic comparative methods to test whether diet or tooth morphology has a greater influence on maintenance of shearing function. Second, these methods will be applied to measure the shearing and crushing/grinding potential from molars of Oligocene and Miocene catarrhines. While extant Old World monkeys have two fully developed lophs on their molars, early members of this clade exhibit partial loph development in some molars. The investigators will test whether these early stages of bilophodonty gave stem cercopithecoids greater persistence of certain tooth functions relative to their non-cercopithecoid catarrhine relatives. Ultimately, this project will contribute to our understanding of the functional origins underlying a key adaptation that contributes to the dietary flexibility and evolutionary success of Old World monkeys.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.