我们最早的祖先也通常生活在林地环境中。
Our earliest ancestors also typically occupied woodland environments.
他们已经会使用工具，虽然我们的祖先还要再过大约200万年才开始制作最早的石刀、石斧等等。
They were primed for tool use, even though it would be another two million years or so before our ancestors began to fashion the first stone blades, choppers and axes.
在我们最早的多细胞生物祖先于数亿年前在地球上出现时，癌症可能就已经存在。
Cancer has probably existed ever since our first multicellular ancestors appeared on Earth hundreds of millions of years ago.
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