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[科学美国人60秒] 【整理】SSS 2009-08-24

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Two years ago Duke University medical center researchers said that the supposedly useless appendix is actually where good gut bacteria safely hide out during some unpleasant intestinal conditions. Now the research team has looked the appendix over evolutionary history. They found that animals have had appendixes for about 80 million years. And the organ has evolved separately at least twice, once among the weird Australian M and another time in the regular old mammal L that we belong to. Darwin thought that only a few animals have an appendix and that ** was what was left of a digestive organ, called the cecum. But the new study found that 70 percent of rodent and primate groups have species with an appendix, and some living animals have a cecum and an appendix. If Darwin had known about species that have both organs, he probably would have revised his views of appendix, the researchers note. Ironically it’s natural selection that keeps the appendix from tricking away completely, because smaller ones are more likely to become infected, and keep your genes out of the pool.
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