Wider, Flatter Noses Evolved in Hotter, Wetter Climates

Our schnozzles are a naturally selected weapon against respiratory disease.

Avsar Aras/Wikimedia

The shape of your nose is at least in part due to the climate of the place where your ancestors came from, according to new research.

A study published Thursday in PLOS Genetics finds that wider, flatter noses are correlated with hotter and more humid environments, and this association is closer than can be explained through random chance alone.

The researchers compared photographs of noses from people of Western African, South Asian, Northern European, and East Asian descent, measuring their width and height. They conducted a statistical analysis to determine if the differences might be explained by genetic drift — normal variation across populations that develop over time — alone. The answer was that much of the differences in human nose shape can be explained by chance, but not all of it. In fact, temperature and humidity appear to play very important roles.

The reason why people in cold places evolved narrow noses while people in hot places evolved wider ones was not explored in the experiment, although the researchers suspect that it may have to do with the way that noses condition air before it reaches the lungs. Part of the function of the nostrils and nasal cavity is to get air to the desired temperature and humidity as you breathe it in, and it could be that different nose shapes allow for this to take place in different ways according to the local environment. The researchers suggest that perhaps variation in nose shape arose as a defense against respiratory disease. This point is provable — it may be possible through further research to show that living in a climate different from your ancestors will put you at increased risk for contracting infectious lung diseases.

Research on human genetic differences across populations is fraught, mostly as a result of a history of using science as means to define racial hierarchies and perpetuate white supremacy. Many geneticists today reject the concept of race as having any scientific merit, and yet your ancestry and the environment where your ancestors came from do define a part of what your look like and who you are.

Will a future of climate change mean that human noses change shape, perhaps becoming flatter and wider as the planet heat up? It’s not terribly likely. For one thing, advances in modern medicine have made infectious disease much less of a factor than it once was, and the number of people dying of pneumonia before they reach childbearing age because they have the wrong nose shape for the climate is likely to be very small. Secondly, for population differences to emerge as a result of natural selection, the populations have to be largely separate over periods of tens of thousands of years. In a world of globalization, humans are less and less separated from another, culturally and sexually.

Genetics are complicated, and climate is only a small piece of the nose shape puzzle. A great deal of difference across human populations is merely a matter of genetic drift, and it’s likely that sexual selection has played a part as well, as people choose mates with a nose that is attractive to them. Random genetic variation and sexual selection are likely to be the primary drivers of human nose shapes into the future. But if you live in a place with a very different climate from the one where your ancestors evolved and you just can’t seem to get rid of that cough, it’s possible your nose is in part to blame.

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