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The size and shape of the nose in different human populations is not simply the result of chance, but evolved, at least in part, in response to local climate conditions, report Arslan Zaidi and Mark Shriver of Pennsylvania State University, in a study published March 16th, 2017, in 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 current study, researchers examined the size and shape of noses on people with West African, South Asian, East Asian, or Northern European ancestry and found that differences in nose shape across these 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 researchers suspect that additional factors, such as cultural preferences when picking a mate, have also played a role in shaping the nose.

Investigations into nose shape evolution and climate adaptation may have medical as well as anthropological implications. Studies of human adaptation are essential to our understanding of disease and yield insights into why certain conditions, such as sickle cell anemia, lactose intolerance or skin cancer, are more common in certain populations. The researchers suggest that it may be worth investigating whether the shape of the nose and the size of the nasal cavity impact one's risk of contracting a respiratory disease when living in a climate that is different from one's ancestors.

"Even though there are substantial differences in nose shape among human populations, much of this variation can be explained by random genetic drift alone. 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 climes," added Zaidi.

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