Climatic adaptation and the human nose: An experimental investigation in living humans

This award was provided as part of NSF's Social, Behavioral and Economic Sciences (SBE) Postdoctoral Research Fellowships (SPRF) program and the Biological Anthropology program. The goal of the SPRF program is to prepare promising, early career doctoral-level scientists for scientific careers in academia, industry or private sector, and government. SPRF awards involve two years of training under the sponsorship of established scientists and encourage Postdoctoral Fellows to perform independent research.

NSF seeks to promote the participation of scientists from all segments of the scientific community, including those from underrepresented groups, in its research programs and activities; the postdoctoral period is considered to be an important level of professional development in attaining this goal. Each Postdoctoral Fellow must address important scientific questions that advance their respective disciplinary fields.

Under the sponsorship of Dr. Scott Maddux at the University of North Texas Health Science Center, this postdoctoral fellowship award supports an early career scientist studying nasal morphology. Humans inhabit diverse environments, ranging from tropical rainforests to Arctic tundra.

The varying climatic conditions of these environments place different levels of stress on the upper respiratory tract, which must ensure that inspired air is sufficiently warmed and humidified to avoid damaging the lungs. As the nose is where most heat and moisture is transferred to air during each breath, differences in nasal size and shape around the globe have been argued to reflect climatic pressures on nasal function.

However, such relationships between nasal anatomy and climatic pressures have not been rigorously tested. Accordingly, this project will investigate associations between nasal form and climate in a large sample of living humans using anatomical data collected from computed tomography (CT) scans, computer modeling of nasal airflow patterns, and internal nasal air temperature/humidity values collected in a climate chamber.

This will thus be the first to directly test whether variation in nasal anatomy and function follow climatic expectations, shedding light on both our evolutionary past and future adaptive scenarios.

Variation in nasal form is believed to be adaptive based on a strong statistical association between nasal morphology and particular climates. However, no studies have empirically linked differences in anatomical structure to different physiological outcomes. Further, a recent analytical shift to Computational Fluid Dynamic (CFD) analysis, used to assess moisture and heat transfer within the nasal passage in silico, has not been validated using in vivo measurements.

This project will test key nasal ecogeographic hypotheses of nasal form and function using a large diverse sample of living participants ranging in age from 18-35-years old. Variation in nasal anatomy will be assessed using cranial CT scans and paired in vivo intranasal air temperature/humidity values collected with a nasal probe in a climate chamber under four different climatic conditions (at room-temperature, cold/dry, hot/dry, and hot/humid).

CT scan data will then be used to perform CFD modeling of nasal physiology which will then be compared to in vivo data to validate CFD results. This project will advance our understanding of human variation, evolutionary adaptations to environment, provide insight into nasal morphologies more susceptible to respiratory issues in particular climate conditions, and potential insight into how nasal form may change in the future.

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.