Up to 85% of people have a vestigial muscle called the " palmaris longus."

多达85％人有一种叫“肌”退化肌肉。

Looking at our primate relatives, we can see that the palmaris longus is sometimes absent in those that spend more time on the land, but always present in those that spend more time in trees.

观察一下灵类动物祖先，可以发现，那些在陆地上生活更久动物有时没有肌，但是，那些在树上生活更久动物总是有肌。