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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 good gut bacteria safely hide out during unpleasant intestinal conditions. Now the research team has looked at the appendix over evolutionary history. They found that animals have had appendixes for about 80 million years. And the organism evolved seperately at least twice, once among the werid Australian marsupials and another time in a regualr mammal lineage that we belong to.
Darwin thought that a few animals have an appendix and that the human version was what were left of digestive organ called caecum. But new study found 70% rodent and primite groups have species with appendixes and some living animals had a caecum and an appendix. If Darwin had known about the species that had both organs , he probably would've revised his views of the appendix,the researchers note.
Ironically, it's the natural selection that keeps the human appendix from shrinking away completely because smaller ones are more likely to become infected and keep your genes out of the pool.
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