Why do fingers and toes prune?

Whenever we take a dip in the pool or in the sea for quite a long time, our fingers and toes always tend to get wrinkly. It’s not entirely bothersome for most people, but have you ever wondered why it happens in the first place?  Pruney fingers and toes have always puzzled scientists but modern experts may now have solved the problem, and have also debunked previous findings as well.

A result of osmosis?

Osmosis is the movement of water molecules through semipermeable membranes and cell walls. When water gets soaked into the skin, parts of the skin start to swell, which results in wrinkly fingers and toes. Scientists initially thought that this process might have been the reason why, but then they noticed that pruney fingers and toes don’t happen to people who had nerve damage to their toes and fingertips.

It turns out that wrinkling was actually a part of an involuntary reaction by our nervous system. Then what’s happening to our skin when soaked in water? Instead of being a result of osmosis, wrinkly fingers and toes are a result of vasoconstriction. When this happens, the presence of water sends a signal through our nerves, telling the blood vessels to constrict or shrink (assuming the nervous system functions properly). Decreasing blood volume makes the arteries, capillaries, and veins appear skinnier, and the skin above them collapses and turns wrinkly.

Wrinkly fingers and toes for better grip

Scientists further studied the phenomenon and asked participants to pick up dry or wet objects including marbles of various sizes. One hand is dry and the other has been soaked in warm water for a few minutes. No differences were found when picking up dry objects with wet or dry hands but surprisingly, there was a significant change when picking up wet objects. Participants picked up wet objects faster with wrinkled hands than with dry hands.

This led to the theory that wrinkly hands work like treads on car tires, giving it better grip in wet conditions. This might have helped our ancestors with gathering food from rivers or wet vegetation. The same effect can in pruney toes could also help us get a secure grip in the rain.

Seeing that wrinkly hands and toes gives us the advantage of getting a better grip, it’s not yet known why our fingers and toes aren’t permanently pruney, according to evolutionary biologist Tom Smulders. There’s still quite a lot to learn from this strange phenomenon in our bodies, and scientists are still on their way to find out the long term effects of wrinkly fingers and toes. For now, enjoy taking a dip in the pool without any worries!