Climate Affects Nose Shapes

Date: 17 March 2017 - 19:22

News ID: ۳۷۸۹۳

WASHINGTON (Dispatches)-According to an international team of researchers, humans inherit their nose shape from their parents, but ultimately, the shape of someone's nose and that of their parents was formed by a long process of adaptation to our local climate.
"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 Mark D. Shriver, professor of anthropology, Penn State. "We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity." The researchers noted today (Mar. 17) in PLOS Genetics that "An important function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tract."
They considered a variety of nose measurements, looking at the width of the nostrils, the distance between nostrils, the height of the nose, nose ridge length, nose protrusion, external area of the nose and the area of the nostrils. The measurements were made using 3D facial imaging.
Differences in the human nose may have accumulated among populations through time as a result of a random process called genetic drift. However, divergent selection -- variation in natural selection across populations -- may also be the reason that different populations have differing noses. Teasing the two apart is difficult, especially in humans.
The researchers found that the width of the nostrils and the base of the nose measurements differed across populations more than could be accounted for by genetic drift, indicating a role for natural selection in the evolution of nose shape in humans. To show that the local climate contributed to this difference, the researchers looked at the spatial distribution of these traits and correlated them with local temperatures and humidity. They showed that the width of the nostrils is strongly correlated with temperature and absolute humidity. The researchers noted that "the positive direction of the effects indicate that wider noses are more common in warm-humid climates, while narrower noses are more common in cold-dry climates."