What your nose knows about human evolution


THEY can be bulbous, pert or pointy, but why do noses look so different from one another? It could have something to do with how humans evolved to live in certain climates, a new study suggests.
In the study, the researchers found that wider noses are more commonly found among people living in warm and humid climates, and narrower noses are more commonly found among people in cold and dry climates.
One possible explanation for why nose shapes vary around the world is genetic drift, which is a mechanism of evolution through which the frequency of certain genes “drifts” upward or downward at random, leading to measurable differences between populations that don’t often mingle.
But for the evolution of some human traits, it’s likely that another mechanism, natural selection, also played a role, the researchers wrote. In other words, the evolution of some traits occurred not solely due to a random drift of genes, but also in response to outside factors. For example, human skin color is thought to have evolved in different human populations in response to the amounts of ultraviolet radiation they were exposed to, the study authors wrote.
To see what mechanism likely influenced nose shape, the researchers used 3D facial imaging to measure the noses of more than 2,600 participants from West Africa, South Asia, East Asia and Northern Europe. The researchers scrutinized the noses, measuring the nostril width, distance between nostrils, nose height, nose-ridge length, nose protrusion and nostril area. In addition, the researchers estimated each participant’s ancestry using genetic testing.
The researchers found that two nose measurements — nostril width and the width of the nose at its base — appeared to be linked to climate. People with wider nostrils were more likely to live in hot, humid climates, and people with narrower nostrils were more likely to live in cold and dry climates, the study said.
The nose’s purpose goes beyond smelling and breathing. It also helps warm and moisten the air before it reaches the lungs. The right temperature and humidity levels are important throughout the respiratory tract, because they help the tiny, hair-like cells that line the tract to keep out germs and allergens.
In fact, the nose is so good at regulating air temperature and humidity levels that the air is already 90 of the way to its ideal temperature and moisture level by the time the air reaches the back of the throat, the researchers wrote.