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What does the weather have to do with the shape of your nose?

What does the weather have to do with the shape of your nose?


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Large, small, wide, narrow, long or short, drooping, flat, aquiline, protruding or prominent. Humans inherit the shape of their nose 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, according to an international team of researchers.

"We are interested in recent human evolution and what explains the obvious variation in things like skin color, hair color and the face itself," says researcher Mark D. Shriver, professor of anthropology at Pennsylvania State University, In America - We focus on features of the nose that differ between populations and look at geographic variation with respect to temperature and humidity. "

The researchers underline in an article published this Friday in "PLOS Genetics" that "an important function of the nose and nasal cavity is to condition the inspired air before it reaches the lower respiratory tract." These experts took into account a variety of measurements of the nose, looking at the width of the nostrils, the distance between the nostrils, the height of the nose, the length of the crest of the nose, the protrusion of the nose, the external area of ​​the nose and the area of ​​the nostrils. Measurements were made with 3D facial images.

Differences in the human nose may have accumulated between populations over time as a result of a random process called genetic drift. However, divergent selection - variation in natural selection between populations - may also be the reason why different populations have different noses. Analyzing the two separately is difficult, especially in humans.

NOSES BROAD IN HOT-HUMID CLIMATES AND NARROW IN COLD-DRY CLIMATES

The researchers found that the width of the nostrils and measurements of the base of the nose differ between populations more than could be explained by genetic drift, indicating a role for natural selection in the evolution of the shape of the nose. the nose in humans. To show that the local climate contributed to this difference, the scientists examined the spatial distribution of these traits and correlated them with local temperatures and humidity.

The researchers note that "the positive direction of effects indicates that wider noses are more common in hot and humid climates, while narrower noses are more common in cold and dry climates." "It all goes back to the Thompson Rule (Arthur Thompson)," explains Shriver. "In the late 1800s, he said that long, thin noses occurred in dry, cold areas, while short, wide noses occur in hot, cold areas. wet. Many people have analyzed the issue with measurements of the skull, but no one had made measurements in living people. "

One purpose of the nose is to condition the inhaled air so that it is warm and humid. Narrower nostrils appear to alter airflow so that the mucous-covered interior of the nose can moisten and warm the air more efficiently, so it was probably more essential to have this trait in cold, dry weather, according to Shriver. . People with narrower nostrils likely evolved and had more offspring than people with wider nostrils in colder climates, leading to a gradual decrease in the width of the nose in populations living far from the equator.

The researchers also found differences between men and women in the characteristics of the nose across the board. This sexual dimorphism is not unusual, as human males tend to be larger than human females, and their noses are therefore typically larger as well.

Shriver believes that differences between populations in nose size can occur through sexual selection - people can choose partners simply because they find a smaller or larger nose more attractive. If an entire group thinks that a small size is better, then those with large noses will be less successful in reproduction and fewer people with large noses will be in the group.

Over time, the nose size in the group will decrease relative to other groups where large noses are prioritized. These notions of beauty can be linked to how well adapted the nose is to the local climate. Ecological selection and sexual selection could reinforce each other, according to the researchers. However, further analysis is required to see if this connection between the two types of selection was important in the evolution of the nose.

Ecotices


Video: Get rid of hook nose u0026 nose hump reduction naturally. Get Straight, Slim u0026 Sharper nose. Exercises (July 2022).


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