Strange fingertips

We all know well the prune-like fingers we get when we are in the bath. Most people think it’s caused by water making the skin in our fingers bigger. In fact, it could be an evolutionary(进化的) feature caused by a reaction in our body’s central nervous system. Rather than the skin getting bigger, fingertips actually shrink when they wrinkle(起皱纹), because the blood vessels(血管) inside them become smaller. The lines could have evolved in our ancestors as they collected food from wet vegetation or streams.

Dr Tom Smulders wanted to test the theory suggested by Mark Changizi in 2011, which said that wrinkled fingers were an evolutionary adaptation. Like treads on tyres, Changizi said that wrinkles served the function of removing water from between the fingers and objects, making it easier to pick things up.

Perfect student project

Smulders saw that it should be easy to prove that wrinkled fingers were better at holding in wet conditions and it was an ideal student project. He explains, “we had the idea of timing how long it takes to move marbles(弹珠) from one container to another, between thumb and index finger. The people in the experiment did that underwater or not underwater, with wrinkled fingers or not wrinkled fingers, so one person did all four conditions.” They found that people are in fact better at moving objects from underwater with wrinkled fingers than with normal fingers.

Adaptation to environment

Whether that means that wrinkled fingers are an adaptation is open to question; it could be a side effect of something that evolved for a different reason. The research suggests that there may be a loss of sensitivity in our hands, which explains why our fingers return to their normal state when not under water.