An anonymous reader quotes a report from The Guardian: Human noses have been shaped by climate, according to research probing variation in the human snout. Researchers say their findings back up the theory that wider nostrils developed in populations living in warm, humid conditions, while populations living in high latitudes, such as northern Europe, developed narrower nostrils as an adaptation to the chilly, dry conditions. Writing in the journal Plos Genetics, researchers from the U.S., Ireland and Belgium describe how they began to unpick variations in nose shape by using 3D facial imaging to take a host of measurements from 476 volunteers of south Asian, east Asian, west African and northern European ancestry. The results revealed that only two out of seven nose-related traits were found to differ more between the populations than would be expected from the impact of random, chance changes in genetic makeup over time. The authors say that suggests variations in those traits have been influenced by natural selection. With further analysis, based on data from participants of west African and European ancestry, confirming that nose shape is highly heritable, the team looked to see if there was a link between nose shape and climate. The results showed that nostril width is linked to temperature and absolute humidity, with participants whose ancestors lived in warm-humid climates on average having wider nostrils than those whose ancestors lived in cool-dry climates. That, says Arslan Zaidi, co-author of the study from Pennsylvania State University, could be because narrower nasal passages help to increase the moisture content of air and warm it -- a bonus for those in higher latitudes.
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