An arched fossilized foot bone found in Ethiopia shows that human ancestors walked upright 3.2 million years ago and were no longer tree dwellers, said a study Thursday in the journal Science.

周四出版的科学杂志上的一个研究声称：从一段在埃塞俄比亚发现的足弓部化石骨骼上研究显示，人类祖先在320万年以前已不再生活在树上而是开始在地上直立行走。

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The bone also shows that A. afarensis had abandoned the flexible midfoot that apes use to grasp tree branches, in favor of an arch that makes upright walking more efficient.

这个骨头也说明南方古猿已经抛弃了猿所具有的用于攀爬树枝的柔韧的足中段结构，由于足弓结构的出现，直立行走变得更有效率。

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Behind the first tree I found a man standing upright.

在第一株树的后面，我看见一个人立着。

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One by one each woman parted from her companions and went to her own plot, whose boundaries were marked by an abandoned termite hill, a fallen tree, and upright boulder.

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