Did you ever wonder why the tips of the fingers wrinkle like a prune when exposed to water for a long period of time? People often think that osmosis causes water to enter the outer layer of skin making the fingertips swell. But since the 1930's, scientists have known that fingertips don't swell or wrinkle when there is nerve damage to the fingers, even with prolonged submersion in water. 

So if it's not osmosis, what causes this phenomenon? A recent study may give us an answer. Mark Changizi, an evolutionary neurobiologist at 2AI Labs in Boise, Idaho, and his colleagues, propose that wrinkling of the fingertips has an evolutionary function. That our nervous system, by causing vasoconstriction of blood vessels below the skin, is responsible for this involuntary reaction that offers an advantage in gripping wet objects.

The study demonstrated that wrinkled fingertips make it easier to grasp objects underwater. Participants in the study had to move dry and wet objects with both dry fingertips, and again, with wrinkled fingertips. The results showed that participants were able to move wet objects 12% faster with wrinkled fingertips than with dry ones. But wrinkled fingertips made no difference when it came to moving dry objects. Basically, when the pads of the fingers are wrinkled, they provide a better grip in wet conditions, like treads on a car tire that increase the surface area of tire on the road. 

So why do our fingertips wrinkle when in water? Our brain causes this evolutionary trait to enhance the gripping ability of the fingers underwater! Perhaps this was beneficial to our ancestors who might have had to gather food from wetlands and streams.

And if it happens to you, don't worry, it goes away all on its own. Skin is truly an amazing organ!