Investigating the case of human nose shape and climate adaptation

Abstract

The evolutionary reasons for variation in nose shape across human populations have been subject to continuing debateAn import function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tractFor 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 climateTo address the question of whether local adaptation to climate is responsible for nose shape divergence across populations, we use Qst–Fst comparisons to show that nares width and alar base width are more differentiated across populations than expected under genetic drift aloneTo test whether this differentiation is due to climate adaptation, we compared the spatial distribution of these variables with the global distribution of temperature, absolute humidity, and relative humidityWe find that width of the nares is correlated with temperature and absolute humidity, but not with relative humidityWe conclude that some aspects of nose shape may indeed have been driven by local adaptation to climateHowever, we think that this is a simplified explanation of a very complex evolutionary history, which possibly also involved other non-neutral forces such as sexual selection.