Why did humans evolve to walk upright?

人类为何进化到了直立行走的姿态？

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Like several of the newly described species, the DogCroc was able to walk upright.

向许多新发现的物种一样，犬鳄可以直立行走。

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We walk upright on two legs and our newborns are helpless. Our babies are unusually large.

我们用两条腿直立行走，我们的新生宝宝非常无助，也大得不寻常。

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New fossil evidence seems to confirm that a key ancestor of ours could walk upright consistently - one of the major advances in human evolution.

BBC: Fossil find puts 'Lucy' story on firm footing

There is some evidence that much older hominids could walk upright.

BBC: NEWS | Science/Nature | Scientists unearth early skeleton

And the voice from Galilee, which would defy Caesar, offered a new Kingdom in which each man could walk upright and bow to none but his God.

WSJ: In Hoc Anno Domini