DDIG: The development and function of the nasopharynx and its role in the evolution of primate respiratory abilities

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This study will use both bony and histological morphology of the nose (nasopharynx) to examine a comparative sample of modern primates and apply that study to answering climatic adaptational questions about Neandertals and Homo heidelbergensis. All methods used to analyze the specimens will be combined to create a three-dimensional map of the nasopharynx. By studying interaction of its hard and soft tissue components, a more robust model of its functional morphology may be derived. Data on normal growth of nasopharyngeal boundaries holds clinical importance with regard to URT diseases, which are the most common pediatric clinical conditions. This project provides previously unavailable data on the normal growth and functional morphologic relationships of nasopharyngeal boundaries, which are directly relevant to URT disease etiology.The nasopharynx comprises a vital portion of the upper respiratory tract. Yet, patterns of morphologic change in this region over human evolution remains poorly understood. This study tests the hypothesis that the bony nasopharyngeal boundaries share a functional relationship with other units of the craniofacial skeleton. As an upper respiratory tract (URT) component, the nasopharyngeal boundaries may be subject to patterns of climatic stress and adaptation. It will thus be tested whether climatic adaptations are present in primate species inhabiting cold, dry environments. To test this hypothesis, CT imaging of nasopharyngeal boundaries will be performed on postmortem samples of macaque monkeys that died of natural causes (Macaca mulatta, Macaca fascicularis) from warm and cold climates. Those from colder environments are expected to exhibit greater nasopharyngal surface area-to-volume ratio, which would increase contact between airflow and nasopharyngeal epithelia for more efficient warming and humidification. Finally, fossil specimens attributed to Neanderthals (from cold, dry climates) and Homo heidelbergensis will undergo Generalized Procrustes Analysis (GPA) of URT landmark coordinate data for comparison with geographically diverse modern human crania. The relationship between nasopharyngeal morphology and histology will also be evaluated via light microscopy of a diverse primate sample.As a Doctoral Dissertation Research Improvement award, it will provide support to enable a promising student to establish a strong independent research career.