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人类经过漫长的进化之后,四肢已经明显变化,有了明确分工,前肢变成了双手,可用于进行生产劳动,创造赖以生存的物质财富,而后肢则变成了双
After long evolution, human limbs have changed obviously. With a clear division of labor, the forelimbs become hands and can be used for productive labor to create the material wealth upon which the survival depends. The hind limbs then become double