{UAH} Fwd: African and European noses evolved for the climate

African and European noses evolved for the climate

Richard Roxburgh as Cyrano de Bergerac. Picture: Chris Pavlich

Cyrano de Bergerac reputedly defended his oversized nose as "the mark of a witty, courteous, affable, generous and liberal man".

The truth, sadly for the swashbuckling Frenchman, is a little more mundane — it is the mark of a man whose ancestors have adapted to their climate.

People of African descent typically have shorter noses, with wider nostrils. People of northern European descent typically have longer, thinner, noses. A new study claims that the reason why is the weather.

The scientists behind the study, from Penn State University, are not the first to suggest this idea. So striking is the relation ­between latitude and nostrils that the Victorian anthropologist ­Arthur Thomson even codified it, calling it "Thomson's nose rule".

His argument was that those living in the cold, less humid, north needed longer, tighter, noses to humidify and heat incoming air.

However, there has always been a competing argument: that variation in nose shape is simply chance. There is a well-known phenomenon called "genetic drift" in which features can change geographically for non-adaptive reasons and it accounts for much of the variation in human appearance.

The new research, published yesterday in the journal PLoS Genetics, has shown that this cannot be the case when it comes to noses, however. By taking measurements of nose features from populations across Africa, South Asia, East Asia and northern Europe, the researchers were able to apply a statistical analysis to show that the variation was greater than could be accounted for by chance alone.

More than that though, they also showed that Thomson's nose rule was very probably the ­explanation. The width and length of noses around the world is strongly correlated with ­humidity and temperature. Even allowing for genetic drift, nostril diameter shows very big changes between populations.

Penn State's Arslan Zaidi said this seemed intuitively sensible. "An important function of the nose is it warms and humidifies incoming air. The reason that's important is, cold and dry air is detrimental to the functioning of the respiratory tract," he said.

When hit by chilly air, the lungs are less good at absorbing oxygen. More than that, the air is also more likely to carry bugs.

"Under good warm humid conditions, mucus traps particles and pathogens before the air reaches our lungs," said Dr Zaidi.

"If the nose is dry and it's not warm enough, the hairs are not able to function as well, which could well lead to respiratory ­diseases."

It was likely changes in shape would only be partially accounted for by climate and that other factors, such as what men and women culturally find attractive in a partner, also come into play.

The Times

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