Subtitles section Play video Print subtitles Whether you're swimming or washing the dishes, or just taking a nice long well-deserved bath, if you're immersed in water for longer than 10 minutes, chances are your fingers and toes will emerge looking like raisins. So what's up with the wrinkle digits? For years, a scientist study the phenomenon was the result of some type of osmosis caused by water passing into the dry outer layer of skin. The influx of water, the thinking wet would expand the skin surface area but not the tissue below its. The skin would bunch up and wrinkled. But in 1935 a pair of doctors noticed that this affects didn't happen in their patients with nerve damage. One patient, for example, was a boy who had lost feeling in three of his fingers The researchers found that when his hands got wet, the fingers that could feel wrinkled as normal, but the ones that were numb, remain smooth. It turned out that the pretty digits weren't caused by just a passive flow of water through the skin, it was an active responsive of the nervous system to prolonged moisture. The nervous system causes the wrinkling by constricting the blood vessel below the skin which causes the upper layers of skin to pucker. Since the phenomenon is caused by an involuntary nervous bound, some biologists have thought that it must have some evolutionary function. But what possible purpose could it serve? One recent theory suggests that wrinkly skin may have given our ancestors a better grip on working in wet conditions, like gathering food from a stream, or damp vegetation May have also given us better footing while walking across the landscapes in the rain. In a 2013 study, evolutionary biologists tested this theory by asking subjects with either wrinkly or non wrinkly fingers to pick up a variety of wet and dry objects like marbles. They found that the subjects with wrinkly digits picked up the wet objects 12 percent faster than their counterparts, but there was no difference when it came to picking up dry objects. The wrinkles apparently helped channel the water away much like the treads on your car's tires. So then this raises the question, if wrinkly skin gives us a better grip, then why isn't our skin wrinkly all the time? Well, maybe because shriveled fingers and toes are less sensitive, which is no advantage at all. Thanks for asking, and if you'd like to submit questions for us to answer, or get these quick questions a few days early check out PATREON.COM/SCISHOW, don't forget to go to YOUTUBE.COM//SCISHOW and subscribe.