Scientific American / Nature magazine
11 Apr 2022
People often assume that wrinkling is the result of water passing into the outer layer of the skin and making it swell up.
But that is not the correct reason.
Scientists think that they have the answer to why the skin on human fingers and toes shrivels up like an old prune when we soak in the bath. Laboratory tests confirmed a theory that wrinkly fingers improve our grip on wet or submerged objects, working to channel away the water like the rain treads in car tires.
Researchers have known that the effect does not occur when there is nerve damage in the fingers. This points to the change being an involuntary reaction by the body's autonomic nervous system. The distinctive wrinkling is caused by blood vessels constricting below the skin.
In the latest study, participants picked up wet or dry objects including marbles of different sizes with normal hands or with fingers wrinkled after soaking in warm water for 30 minutes. The subjects were faster at picking up wet marbles with wrinkled fingers than with dry ones, but wrinkles made no difference for moving dry objects.
Wrinkled fingers could have helped our ancestors to gather food from wet vegetation or streams. The analogous effect in the toes could help us to get a better footing in the rain.
Given that wrinkles confer an advantage with wet objects but apparently no disadvantage with dry ones, it's not clear why our fingers are not permanently wrinkled. A possible reasoning may be that this could diminish the sensitivity in our fingertips or could increase the risk of damage through catching on objects.
Your content has been submitted
Your content has been submitted
Your content has been submitted