Baonhu Nguyen Tran

Given the well-established role of the nose in heating and humidifying inspired air, ecogeographic variation in modern human nasal morphology is commonly attributed to climatic adaptation. However, anthropologists have also hypothesized that the nose may play an important—but underappreciated—role in both whole-body and brain thermoregulation across globally diverse populations. Yet, few attempts to experimentally investigate these hypotheses have been undertaken. Accordingly, the proposed study is specifically designed to test hypotheses regarding the role of the respiratory system in both whole-body and brain thermoregulation in a large, morphologically-diverse sample of living humans. This will be accomplished by 1) precisely quantifying heat losses from both the respiratory and integumentary (skin) systems of living human subjects exposed to different environmental conditions in a climate-controlled chamber, 2) accurately assessing respiratory influences on brain thermoregulation from these subjects through the use of a cutting-edge technology (i.e., microwave radiometry) for non-invasively measuring internal brain temperatures, and 3) employing these physiological variables in conjunction with CT-based measures of 3D nasal morphology from the same human subjects to explicitly test evolutionary hypotheses regarding form-function relationships.