To address the question of whether local adaptation to climate is responsible for nose shape divergence across populations, this study used Qst-Fst comparisons to show that nares width and alar base width are more differentiated across populations than expected under genetic drift alone.
The evolutionary reasons for variation in nose shape across human populations have been subject to continuing debate. An import function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tract. For this reason, it is thought the observed differences in nose shape among populations are not simply the result of genetic drift, but may be adaptations to climate. To test whether this differentiation is due to climate adaptation, the current study compared the spatial distribution of these variables with the global distribution of temperature, absolute humidity, and relative humidity. It found that width of the nares is correlated with temperature and absolute humidity, but not with relative humidity. The researchers conclude that some aspects of nose shape may indeed have been driven by local adaptation to climate; however, they view this as a simplified explanation of a complex evolutionary history, which may involve other non-neutral forces, such as sexual selection. (publisher abstract modified)