“My lords, there is no such nose as that nose – You cannot look upon it without crying: ‘Oh, no, Impossible! Exaggerated!’” And so we are introduced to Cyrano de Bergerac and his most distinguishing feature. We might not be able to do much about the shape of our noses, but new research has revealed what may cause it: climate.
The study, by an international team and published in PLOS Genetics, has revealed that particular nose shapes may have developed through natural selection in response to local climates. They demonstrated that flatter noses with wider nostrils adapted for warmer, humid climes, while narrow nostriled noses developed for cold, dry conditions.
It had been thought that “recent” evolutionary differences in nose shape was caused by the random process known as genetic drift, but the researchers backed the theory that it was actually divergent selection – a variation in natural selection across different populations – that had caused them, and climate was the driver.
"We are interested in recent human evolution and what explains the evident variation in things like skin color, hair color and the face itself," said co-author Mark D. Shriver from Penn State University in a statement. "We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity."
To do this, they used 3D facial imaging to take measurements from 476 volunteers of West African, south Asian, east Asian, and northern European ancestry.
They found that the measurements of the noses differed across the populations more than random genetic drift would allow for. They then looked at the width and spatial distribution of the nostrils and correlated them with the local temperatures and humidity of where the volunteers and their ancestors were from.
They discovered that the width of the nostrils strongly correlated with temperature and absolute humidity, which indicated that “wider noses are more common in warm-humid climates, while narrower noses are more common in cold-dry climates."
“We conclude that some aspects of nose shape may indeed have been driven by local adaptation to climate,” the authors wrote. “However, we think that this is a simplified explanation of a very complex evolutionary history,” and suggest further study into sexual selection as well.
Artistic representation of their findings, showing wider nostrils in red and narrower nostrils in blue, which also represent climatic variation in temperature and humidity, to show that narrower nostrils are favored in cool-dry climates, while wider nostrils are favored in hot-humid climates. Arslan A. Zaidi and colleagues.