Take a long soak in the bath, and your fingers transform into little elderly folk. Draw on some eyes and thick corrective lenses, and you’ve got a retirement home in the palm of your hand.
It’s a fun, if a little creepy, natural occurrence of our bodies. And one that the scientific world has recently learned might have a possible evolutionary advantage while also potentially being used as a health diagnostic tool, according to the BBC’s Richard Gray.
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For decades, when asked about why our fingers prune in water, scientists would shout “osmosis!” and then run away to avoid follow-up questions. The idea was that water seeps into skin cells, they swell up, and her skin starts folding and twisting in on itself in response.
That’s probably not what’s happening. After all, people with nerve damage in their hands don’t get wrinkly fingers. Turns out, the process is controlled by the nervous system. When submerged, blood vessels constrict, reducing volume beneath the skin and triggering the classic wrinkle.
This Is Why Fingers and Toes Wrinkle in Water
Recent research found that the patterns of those water-induced wrinkles aren’t random, either. The pattern is consistent every time, kind of like a fingerprint, shaped by how your skin is anchored to everything below it.
As for why they wrinkle, as in what possible purpose could such a response even serve, it all has to do with grip. To improve our grip in wet environments, our hands and feet, our primary tools for traversal, evolved to respond to the moisture by, essentially, developing tire treads to be extra grippy.
In early human, navigating wet rocks or foraging underwater would have a little bit of an advantage once they soaked their extremities for long enough that their fingers gained a +10 grip score.
That sounds like it would be handy to have all the time. So why only prune in response to water? That is a little trickier for science to answer. The leading theory is a bit complex and a little heady, so try to follow along if you can: it feels gross!
The speed and symmetry of this wrinkling might be a kind of biofeedback. It takes about 3 ½ minutes for a soaking hand to become wrinkly. People with type 2 diabetes, cystic fibrosis, nerve injuries, or even early-stage Parkinson’s show delayed, excessive, or asymmetrical wrinkling.
The response, or lack of it, is enough for researchers and doctors to explore using finger wrinkling as a cheap, noninvasive way to screen for health problems like nervous or cardiovascular issues.
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