Investigating Genetic Mechanisms of the Baboon Dentition

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The primate dentition has been studied for many reasons ranging from phylogenetic reconstruction to dental development to functional morphology. Because of their composition, teeth are the most frequently preserved parts of fossil primates and the only ones known for some extinct taxa. Teeth are adapted for many functions - e.g. mastication, food preparation, and social interactions - but also contain a record of their growth, which all means that a great deal can be learned from their fossilized forms. The dentition is also important from the developmental and evolutionary perspective. Only wear, breakage and caries alter the morphology of primate teeth once eruption has occurred, and the effects of these processes are fairly easy to identify. Teeth are thus relatively less affected by environment and behavior than are bones. Consequently, teeth have a reduced nongenetic component to their variation and are more tractable for determining underlying genetic mechanisms. Combining all these characteristics of teeth, the dentition is a prime candidate for investigating the genetic evolutionary history of a complex phenotype. This project proposes research into the genetic evolutionary history of the primate dentition using a baboon model. This project is a novel integration of the usually disparate fields of quantitative genetics and paleontology in order to investigate and identify the genetic mechanisms underlying evolutionarily significant morphological variation. This project identifies dental traits from the last five million years of baboon evolution in Africa that also vary in a genotyped pedigreed colony of modern savanna baboons at the Southwest Foundation for Biomedical Research in San Antonio, Texas. This variation will then be studied using modern quantitative genetic analyses to identify the genetic mechanisms that underlie this variation in modern baboons, and thereby, probably represent the same mechanisms that determined this variation in past baboon species. This project represents a unique opportunity to integrate the power of modern genetics with the time depth of the fossil record to investigate the genome and anatomy simultaneously, rather than as separate entities. Results from this study have broad implications for evolutionary and developmental biology, as well as for anthropology and primatology. This study will provide insight into the genetic mechanisms that underlie tooth development and patterning in baboons, mechanisms likely to be involved in the evolution of teeth of other primates, including humans and their ancestors. Thus, the results of this study will be immediately applicable to the study of human dental evolution, as well as the evolution of many other primates.