Scientists say our fingers get pruney when wet for a better grip.
Why do our fingers and toes wrinkle up like prunes when we've been in the water for a while?
Maybe you've heard that it's because of water passing into the outer layer of skin, making it swell with wrinkles -- but it turns out that that explanation is all wet.
The real reason is that blood vessels just under the skin constrict as an involuntary nervous system reaction to skin's immersion in water. This causes the upper layers of skin to pucker and wrinkle.
Scientists figured this out by observing that the skin of people with nerve damage did not prune up when exposed to water. Voila.
"But why did our bodies, actually just our fingers and toes, evolve to react this way when wet?" Eric Schulze, host of Smithsonian magazine's online video series "Ask Smithsonian," asks in a new episode. "Maybe we wrinkle, so like tire treads, our fingers and toes can get better traction in wet conditions."
In fact, a 2013 study conducted by scientists at Newcastle University in England showed that wrinkled fingers do improve the handling of wet objects. But a separate 2014 study conducted at the Max Delbrück Center for Molecular Medicine in Berlin, Germany found no such effect.
So, what gives?
"I don’t think either study was good," Dr. Mark Changizi, a theoretical neurobiologist and director of human cognition at 2AI Labs in Boise, Idaho, who has studied prune fingers, told Smithsonian.
He said that, while we now know how our fingers shrivel up when wet, more research is needed to validate why.
(h/t Smithsonian)
