What do you think of this fact?
Stay in the bath long enough and your fingertips look like raisins. The obvious explanation: your skin soaks up water and swells. Except that’s not the whole story.
Your nerves are in charge
According to Newcastle University, the wrinkles form because blood vessels beneath the skin constrict. That constriction is controlled by the autonomic nervous system, the same system that runs things like your breathing and heart rate without you thinking about it.
The strongest clue has been around for decades. Nature News, republished by BioEd Online, reports that it has been known since the 1930s that the wrinkling doesn’t happen when the nerves in a finger are damaged. If it were just skin soaking up water, the nerves wouldn’t matter. Smithsonian Magazine calls it what it is: an active process, not your skin passively getting soggy.
Built-in tire tread?
So why would your body bother? Smithsonian Magazine describes a 2011 paper which found that the wrinkles follow consistent patterns that let water drain away, a bit like the tread on a tire.
In 2013, a team at Newcastle University put that idea to the test. According to Smithsonian Magazine, 20 volunteers soaked their hands in warm water for 30 minutes and then moved wet glass marbles and fishing weights from one container to another. With wrinkled fingers, they moved the wet marbles 12 percent faster. With dry marbles, the wrinkles made no difference. The study appeared in the journal Biology Letters.
Bonus fact: It’s not just your fingers. The Newcastle press release is titled “why we get wrinkly fingers and toes”, and the researchers suggest wrinkled toes may have helped our ancestors get a better footing in the rain.
So your pruney fingertips aren’t a design flaw. They’re your body switching into wet-grip mode, all on its own.