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Earlier humans had a tail with appendix bone. But now the tail has disappeared. Why?
Answer 1:

Good question. Scientists call the human tailbone a vestigial structure. For monkeys, tails are an important body part that helps them keep their balance--this is part of the reason that they are so good at moving around in the trees.

Scientists think that, near the end of the time period when humans had tails, they no longer had a useful function like this. There may even have been some reason that having a tail was actually a bad thing, for example for the prospects of finding a mate or just for surviving. So most scientists believe that over time, the humans that were the best at passing on their genes were the ones that didn't have tails. We call this evolution: we think that humans evolved to lose their tails.


Answer 2:

Good question. Humans are apes, and no apes have tails, but our relatives, the monkeys, do. I don't think anybody has a good idea of why apes lost their tails.



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