Fingers and toes become wrinkled after being in water for long periods, and now new research explains why. The transformed skin improves our grip on wet objects.
Aside from answering why we get the wrinklies after bathing, swimming and hand-washing dishes, the discovery- published in the latest Biology Letters- provides an intriguing clue as to how our ancestors lived.
Clearly they spent a fair amount of time in water, possibly wading around to get fish and plants. Our skin must have evolved to improve the outcome of such tasks, with the wrinkling still useful to us today.
“We have shown that wrinkled fingers give a better grip in wet conditions,” co-author Tom Smulders of Newcastle University was quoted as saying in a press release. “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,” he continued. “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.”
The old theory was that skin on our digits wrinkled when wet due to water passing into the outer layer of skin, making it swell.
Now it’s known that the distinctive wrinkling is caused by blood vessels constricting below the skin. This is controlled by the autonomic nervous system, which handles bodily processes such as breathing, heart rate and perspiration.
For 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. The test subjects were faster with the wet marbles if their fingers were wrinkled. However, wrinkled fingers made no difference for moving dry objects. Wrinkled fingers and toes therefore serve the function of improving our grip on wet objects. (Sex wasn’t mentioned in the study, so I’ll refrain from taking the story in that direction…)
On a serious note, the findings raise the question as to why we don’t have permanently wrinkled fingers. Smulders and his team would like to investigate that further.
“Our initial thoughts,” he said, “are that this could diminish the sensitivity in our fingertips or could increase the risk of damage through catching on objects.”