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Water-Wrinkled Fingers Hold Evolutionary Purpose

Thu, 01/10/2013 - 8:13am
Newcastle Univ.

Image from Fir0002/Flagstaffotos. Used under the GFDL license: http://www.gnu.org/copyleft/fdl.htmlWrinkly fingers caused by soaking them in water for a long time, such as in the bath or doing the dishes, have been shown to improve our grip on wet objects or objects under water.

Scientists at Newcastle Univ. studied people taking objects out of water with wrinkled fingers and again without wrinkled fingers to explain why the effect occurs.

Author Tom Smulders, publishing the paper in Biology Letters says, “We have shown that wrinkled fingers give a better grip in wet conditions – it could be working like treads on your car tires which allow more of the tire to be in contact with the road and gives you a better grip. Going back in time this wrinkling of our fingers in wet conditions could have helped with gathering food from wet vegetation or streams. And as we see the effect in our toes too, this may have been an advantage as it may have meant our ancestors were able to get a better footing in the rain.”

When our hands or feet are in water for a long time, we get wrinkles. Once it was believed that this was the result of water passing into the outer layer of the skin making it swell up, but now it’s known that the formation of these wrinkles is an active process. 

The distinctive wrinkling is caused by blood vessels constricting below the skin controlled by the autonomic nervous system which controls bodily processes such as breathing, heart rate and perspiration.

As it is an active process, this suggests it may have an important function. But it’s only now that scientists have been able to show that wrinkly fingers could offer an advantage.

In the study, people picked up marbles of different sizes with normal hands or with wrinkled fingers after having soaked their hands in warm water for 30 minutes. They were faster with the wet marbles if their fingers were wrinkled. However, wrinkled fingers make no difference for moving dry objects. This suggests that the wrinkles on fingers and toes serve the function of improving our grip on objects under water or maybe even wet objects in general.

Smulders adds, “This raises the question of why we don’t have permanently wrinkled fingers and we’d like to examine this further. Our initial thoughts are that this could diminish the sensitivity in our fingertips or could increase the risk of damage through catching on objects.”

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