But new research that examined the differences in the populations ofthe world may have the answer. And it seems that the local climatemay have contributed to the variations of the form in the evolution of the nose. Pennsylvania State University scientists looked at the sizeand shape of the noses of people with West Africa, South Asia, East Asia and Northern European ancestry. The researchers studied 476 people to discover common traits, which is then discussed in 140 people. The majority of these people were of the U.S. population, but some were also from Europe. The team hopes to discover whether random or natural selection were responsible for 'recent' evolutionary differences in noses. These tend to have developed on tens of thousandsof years. The Penn State team in comparison with a variety of measurements of the nose, which were made using 3D facial Imaging. The researchers found that more noses are more common in warm, wet climates while narrower noses are usually found in cold and dry environments. And their results suggest that natural selection played a large role, with variations between the major groups that would allow a simple chance. Research also suggests that it may be worth investigating if the risk of respiratory disease is greater when you live in a climate different from our ancestors. Arslan Zaidi is co-author of the studyand a doctorate at Pennsylvania State University.Speaking to Satan, he said: ' all aspects of the shape of the nose that we studied, only thewidth of the nose stands out as more different populations than expected by chance. 'Most of the phenotypic and genetic variation among human beings exists within populations, not between them.' features such as width of nose and skin pigmentation have evolved fasterthan most other features probably due to natural selection due to exposure to the environment. ' They are the exception rather than the rule. In fact, most of the genome varies little among populations.
' This is important because often people focus on differences and ignore the similarities. ' Mr Zaidi and his colleague Mark Shriver examined the width of the nose, distance between the nostrils, the height of the nose, length of crest of nose, nose salient, external area of the nose and nostrils area. Looked at the distribution of these traits throughvarious global populations and had compared with the temperaturesand humidity in each area. They found that the width of the nostrils is strongly correlated with temperature and humidity.
More narrow nostrils alter air flow so that the mucosa in the nose can humidify and warm the air more efficiently.
People with narrow nose, therefore, it fared better in colder climatesand probably had more offspring than those with wider nose. This led to a gradual decrease in the width of the nose in the populations that live far from the Ecuador. A former scientific theory suggests thatthe air temperature and humidity can alter noses. But if the differences arose in response to local climates or simply due to chance it wasunknown. Dr. Shriver, Professor of anthropology, Penn State, said: 'Itwas back to Thompson rule.' in the late 1800s Arthur Thompson saidthat you long and thin nose occurred in the areas dry, cold, while short and wide noses occurred in hot and humid areas. 'Many people have tested the issue with measures of the skull, but nobody had measurements in live people.' nose and nasal cavity are keys for the refurbishment of the air we breathe, making is hot and wet when you get to the lungs, which can help prevent infections
But this is not the only explanation for the variation of the shape of the nose in humans. Sexual selection may also have played a role, with people choosing companions because they find more attractive a nose smaller or larger. If one thinks of all small group is better, peoplewith large noses you will struggle to find a mate, one will reduce thenumber of people with large noses. These notions of beauty may be linked to the nose as well adapted to the local climate.
0 komentar:
Posting Komentar