ISLAMABAD: Though you undoubtedly inherited your distinctive nose from your parents, its shape was sculpted over time by adaptations to your ancestors' local climate, suggests a study published in the journal PLOS Genetics on Thursday.
There's a great variety in nose variation from person to person, yet if you look at different ethnic populations, you will see differences across groups. For example, the distance between the wings of the nose, also known as "nasal alare," are larger in people of West African, South Asian and East Asian ancestry than in people of European ancestry.
So it's easy to understand why many people, past and present, "have this sense that human populations are very distinct and have been separated for a long time," said Mark D. Shriver, lead author of the study and a professor of anthropology at Penn State University. Still, he noted, "human populations have always split and come back together, split and come back together, so there's no separate origin."
In fact, genetic differences between various population groups is not that great. Using noses as just one example, said Shriver, "the surface, the appearance of people in different populations is much greater than what the genetic differences show on average."
To answer this question, Shriver and his colleagues selected 2,637 individuals from a database of about 10,000.
They selected people from four populations: North Europeans, South Asians, East Asians and West Africans. Shriver and his team looked at 3-D photos of each individual and examined 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 area of the nostrils.
"So we have multiple cameras that image a person's face, either simultaneously or in a carefully constructed series, and from those multiple angles, you can derive the shape of a face as a point cloud," Shriver said. The resulting 3-D image allows you to "take careful measurements usually calibrated down to a tenth of a millimeter," he said.
Through complex analysis of the data, the researchers learned 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.
Genetic drift refers to the fact that some people leave behind more descendants (and therefore more genes) than others just by chance and not necessarily because they are healthier or better survivors.
If not genetic drift, then natural selection must have played a hand in the evolution of nose shape in humans. Natural selection refers to the fact that people better adapted to.