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。
These species also differ morphologically: grass dwellers are slender with long tails, tree-dwellers are stocky with long legs, twig dwellers are slender but stubby-legged.
这些物种在形态上也有所不同：呆在草上的动物体型纤细，尾巴很长；呆在树上的动物体格健壮，腿长；而呆在树枝的动物体型纤细，但腿短。
Yet despite its high cost, creatures ranging from ground dwellers to tree climbers and even flyers do it.
尽管这些花费过多，从地上居的到树上爬的，甚至天上飞的动物们都会去做。
应用推荐