WASHINGTON, March 18 (Xinhua) -- If you are not satisfied with the shape of your nose, blame it on climate, not your parents or grandparents.
In a study published this week in the journal PLOS Genetics, researchers from the Pennsylvania State University found that human noses may have been shaped, at least in part, by a long process of adaptation to local climate conditions.
Generally, wider noses are more common in warm and humid climates, while narrower noses are more common in cold and dry climates, it said.
The findings were based on an examination of the size and shape of noses on people with West African, South Asian, East Asian, or Northern European ancestry.
The researchers looked 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 by using 3D facial imaging.
It showed that the width of the nostrils is strongly correlated with temperature and absolute humidity, but not the result of a random process called genetic drift.
One purpose of the nose is to condition the air that we breathe, to ensure that it is warm and moist when it reaches the lungs, which helps to prevent infections.
The current study found the narrower nostrils seem to alter the airflow so that the mucous-covered inside of the nose can humidify and warm the air more efficiently.
"It was probably more essential to have this trait in cold and dry climates," it said.
"People with narrower nostrils probably fared better and had more offspring than people with wider nostrils, in colder climates. This lead to a gradual decrease in nose width in populations living far away from the equator."
The nose has had a complex evolutionary history, however, and researchers suspected that additional factors, such as cultural preferences when picking a mate, have also played a role in shaping the nose.
Investigations into nose shape evolution and climate adaptation may have medical as well as anthropological implications.
Studies of human adaptation are essential to our understanding of disease and yield insights into why certain conditions, such as sickle cell anemia, lactose intolerance or skin cancer, are more common in certain populations.
The researchers said that it may be worth investigating whether the shape of the nose and the size of the nasal cavity impact one's risk of contracting a respiratory disease when living in a climate that is different from one's ancestors.