Humans inherit their nose shape from their parents, but ultimately, the shape of someone’s nose and that of their parents was formed by a long process of adaptation to local climate, according to a study published in the journal PLoS Genetics.

The nose is one of humanity’s most distinctive facial features, which also has the important job of conditioning the air that we breathe, to ensure that it is warm and moist when it reaches the lungs, which helps to prevent infections.

Previous studies suggest that people whose ancestors lived in hot, humid places tend to have wider nostrils than people whose ancestors came from cold and dry environments, but whether these differences arose in response to local climates or just due to chance was unknown.

In the new study, an international research team led by Penn State Professor Mark Shriver examined the size and shape of noses on people with West African, South Asian, East Asian, or Northern European ancestry.

The team considered a variety of nose measurements: the width of the nostrils, the distance between nostrils, the height of the nose, nose ridge length, nose protrusion, external area of the nose, and the area of the nostrils.

“We are interested in recent human evolution and what explains the evident variation in things like skin color, hair color and the face itself,” Prof. Shriver said.

“We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity.”

The researchers found that differences in nose shape across the studied populations are greater than can be explained by chance alone.

Additionally, wider nostrils are correlated with ancestors who evolved in warmer temperatures and with greater absolute humidity, suggesting that climate was one factor driving nasal evolution.

The nose has had a complex evolutionary history, however, and the scientists suspect that additional factors, such as cultural preferences when picking a mate, have also played a role in shaping the nose.

“Even though there are substantial differences in nose shape among human populations, much of this variation can be explained by random genetic drift alone,” said Penn State researcher Arslan Zaidi, first author of the study.

“This finding is in line with the consensus that most human variation is shared among populations and primarily due to genetic drift.”

“Traits like skin pigmentation and nostril width are exceptions rather than the rule. Having said that, these traits are important to study because they are likely tied to our health, especially as we become more of a global community and migrate to new climates.”

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A.A. Zaidi et al. 2017. Investigating the case of human nose shape and climate adaptation. PLoS Genet 13 (3): e1006616; doi: 10.1371/journal.pgen.1006616