Climate may have helped shape the human nose and determined whether a person is born with a beak or a turnip, research suggests.
Noses come in a huge array of shapes and sizes - big, small, long, short, flat, bulbous, narrow or turned up.
Random genetic changes account for some of the differences, but new evidence points to climate having an impact that is not to be sniffed at. Scientists found that nose measurements of people with African, Asian and European ancestry were too different to be explained by chance alone.
But there were strong correlations with climate and humidity. Wider noses and nostrils were more common in warm, humid conditions while narrower noses led the way in places that were cold and dry.
"We are interested in recent human evolution and what explains the evident variation in things like skin colour, hair colour and the face itself," lead researcher and anthropologist Professor Mark Shriver said.
"We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity."
One important function of the nose and nasal cavity is to "condition inspired air before it reaches the lower respiratory tract", the scientists writing in the journal 'Public Library of Science Genetics' said.
Ideally, inhaled air should be warm and moist. For this reason, narrow nostrils that help the airflow to be humidified by the mucous-covered nasal cavity would have been an advantage to human ancestors moving to colder, drier regions away from the equator.
Natural selection would favour wider nostrils in hotter, stickier parts of the world. The same idea was previously proposed by Oxford University anatomist Professor Arthur Thomson, who came up with Thomson's Nose Rule in the 1800s.
Sexual selection may also have played a role in moulding the human nose, the professor said. Members of a particular group may simply find larger or smaller noses more attractive. If smaller noses are preferred, over time nose size in that population will shrink.