Do you blame (or thank, depending on how you feel about it) your parent for the shape of your nose? You may well have the same big, broad or bulbous nose as your mom or dad, but there’s more to it than that, according to research published in PLOS Genetics.
An international team of researchers, including Mark D. Shriver, professor of anthropology at Penn State, found that the shape of someone’s nose (and that of their parents) was formed over centuries of adaptation to their local climate. “We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity,” said Shriver.
The team used 3D facial imaging to take a variety of nose measurements, including the width of the nostrils, the distance between the nostrils, the height of the nose, the length of the nose ridge, and the nose protrusion. (Want to know more about your nose? Here’s a day in the life.)
Acknowledging that differences in the shape of the human nose may come down to a random process called genetic drift, the researchers also established a role for natural selection. To demonstrate that the local climate contributed to the differences in the width of the nostrils and the base of the nose measurements, the researchers correlated the spatial distribution of these traits with local temperatures and humidity. They showed that the width of the nostrils is strongly correlated with temperature and absolute humidity, noting that “wider noses are more common in warm-humid climates, while narrower noses are more common in cold-dry climates.”
One of the jobs the nose performs is to condition inhaled air, making it moist and warm. Narrow nostrils appear to change the airflow so that the inside of the nose can humidify and warm the air more efficiently, which is more essential, both in terms of health and reproduction, in cold, dry climates. (Don’t miss these 13 strange body facts, explained.)
“It all goes back to (Arthur) Thompson’s Rule,” according to Dr. Shriver. “In the late 1800s he said that long and thin noses occurred in dry, cold areas, while short and wide noses occurred in hot, humid areas. Many people have tested the question with measurements of the skull, but no one had done measurements on live people.”
Shriver also cited sexual dimorphism (men tend to have larger noses than women) and sexual selection (whether people prefer smaller or larger noses in their sexual partners) as explanations for nose shape difference in humans.