Why do our fingers get wrinkly in water, but the rest of our skin doesn’t?
In: Biology
We’re not sure! A leading theory is that it improves our grip in water, but it’s not a settled debate at all.
It may not have a reason… evolution is a collection of fortunate mistakes that still work. Not all of them have a purpose. It could just be a fluke of palm/sole-skin (versus hair-growing normal skin).
Wrinkly or Pruney fingers is actually a nervous system reaction to being in water, not our skin “absorbing” water. Which is why other parts of the body don’t also “absorb” water and get wrinkly/pruney.
Now we don’t know 100% for sure why our bodies decide to do this, but the theory (that I personally believe is true and will get proved if there’s more studies) is that the wrinkly skin gives it more surface area and grip, like treads on a tire, meaning if you’re walking around or climbing across a creek or river or slippery rocks in water, you’ll be able to get a better grip and be less likely to slip
It’s a reflex we are not certain of the purpose of.
And yes, it is a neurologically mediated reflex and not just your skin swelling from absorbing water. If your hand is paralyzed or numbed by a local anesthetic your fingers won’t wrinkle in water.
It’s an active response not a “skin absorbing water” type of thing. We know this because people with nerve damage in their hands or arms don’t have this response and their hands doesn’t get wrinkly in water! If the “I’m in water” signal can’t reach from the hands to the brain, the wrinkles don’t happen, so we know it’s an active process not just passive absorption, because then it would happen whether you can feel your hands or not.
As for why it happens, leading theory is for better grip on wet objects and underwater surfaces. That makes sense with how it happens on your feet in water eventually too. Only hands and feet get pruny, and that’s everything you grab and grip with.
Also, the mechanism seems to be small blood vessels in the hands and feet constricting. So your hands and feet slightly shrink, leaving the skin fitting like a glove that’s too big – hence the wrinkles. Once you dry off, the blood vessels open up again, your hand and feet re-inflate, and the skin fit more snugly again.
Source+ more info:
[Why Water Turns Fingers and Toes Into Prunes (clevelandclinic.org)](https://health.clevelandclinic.org/why-water-makes-your-skin-look-like-a-prune-and-not-a-plum)
Because you don’t grab things with the rest of your body, so grip is irrelevant. You need grip to grab on to wet things without slipping, wrinkly things have more grip than flat things, that’s why your hands get wrinkly.
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