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philosopher2008
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もう一つのありそうな理由は、体毛には寄生虫がわくが、動物の毛皮を使えば取り替えることもできるし、洗濯もできるというのがある。これはまず寄生虫を避けるために体毛が退化し、後にアフリカを出て寒冷地に住むようになってから毛皮を着ることを学んだと考えられる。
最近は人類の進化は遺伝子で調べられており、我々は全身に体毛の生える遺伝子を持っているが、その働きが止まっている状態だという。
このような研究は無駄のように思えるが、実はそのメカニズムが解明されれば頭髪等の増毛の研究に役立つ という。
Many mammals have body hair. Chimpanzee, gorilla and orangutan that are genetically close to human being have fur. We do not know yet why and when humans lost their body hair, because hair is not fossilized. Dominant hypothesis for human's hair loss is to cool body. Chasing prey for long time early human sweated a lot, but body hair kept heat from dissipating quickly. Based on this theory scientists estimate that human has lost body hair 2-1.5 million years ago. The comment on this theory is that none has grown their hair back despite currently living in cold regions. But less than 0.1 million years since humans left Africa is too short for them to get hair back.
Another likely theory says that we would have suffered from fewer parasites without fur, and by wearing animal's fur, we can change or wash it. This view suggests that human had lost hair before leaving Africa, and learned to wear animal's fur after living in cold region.
It has been found that humans have the genes for body hair, but the genome regulation stops them from being expressed.
This research on our body hair may be useful for people who want to prevent balding.
