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   Have you ever noticed that your fingers are wrinkled (有皱纹的) when you’ve just finished swimming or ______ cloths? It seems ______ your hands have aged 30 years in a short time. But is this an accident? Or is it something that nature has built into our bodies?

The wrinkles looked a bit ______ the patterns on the bottom of the running shoes. So ______ made a guess that wrinkles on fingers might be able to help the hanks hold things better.

To test this, researchers asked 20 people to pick up marbles (弹珠) from water ______ their hands. But ______ they started to pick up the marbles, half the people had to keep their hands in water for half an hour.

The researchers discovered the people who had wrinkled fingers completed the task faster that those whose hands were dry. But when they ______ to move dry marbles, all the people performed the same, no matter whether ______ had the wrinkled fingers or not.

Our ancestors might not play with marbles, but wrinkled fingers could make ______ easier for them to climb around in the wet forests and catch fish from ______.

Similarly, our feet ______ get wrinkled in water. This may develop from our ancestors’ need to run ______ the wet ground.

But the question is, if wrinkled fingers are so helpful, ______ don’t our hands just stay that way all the time? In fact, there ______ several disadvantages about wrinkled fingers. They make us feel ______. And wrinkled fingers don’t have enough sense of touch