Climate Had a Hand in Shaping the Human Nose (IMAGE)
Caption
It is thought that differences in nose shape evolved across human populations as a result of local adaptation to climate, and not merely due to genetic drift. By comparing phenotypic and genetic differentiation across populations, we show that while most aspects of nose shape seem to be evolving neutrally, the width of the nares shows signals of climate adaptation. The figure is an artistic representation of our findings. The diverging tree represents the evolutionary process underlying population-differentiation in nose shape, a quantitative trait. Blue boxes represent alleles for narrower nares while red boxes represent alleles for wider nares. Colors in between represent intermediate phenotypes. The color scale was chosen to correspond with color scale representing climatic variation in temperature and humidity, to show that narrower nares are favored in cool-dry climates while wider nares are favored in hot-humid climates. Studying phenotypic differentiation across populations can be tricky in making evolutionary inferences because of the confounding effects of genetic and environmental factors. This limitation can be overcome to a certain extent by studying the phenotypic and genetic variation in admixed populations.
Credit
Arslan A. Zaidi and colleagues.
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