After much consideration, a new theory has been advanced as to why half an hour in a bathtub makes fingers look like they're a billion years old. Finger wrinkles might not be a structural failure. They might be a tactical advantage.
There are plenty of reasons to stay in the tub; a good book, a cold evening, a spider crawling on the shower curtain which might fall on you if the curtain were pushed aside. No matter what it is that keeps you in, there is at least one reason to get out; mummy hands. Fingers wrinkle extravagantly if left in water for too long. There have been plenty of possibilities put forward as to why the skin on hands and feet folds like origami in water. The latest thought, advanced by a neurobiologist, is our fingers wrinkle for the same reason tires have treads. They need better grip.
Researchers studied photos of many different pruned-up hands and noticed that in each, the patterns were similar. The wrinkles didn't intersect with eachother. Instead they curved down from the central tip of the finger to the outside of the finger pad. When the hand grips something, it squeezes the pad of the finger against the object's surface. If the pad of the finger has a uniform surface, and the surface or the finger is wet, water can get trapped there and take away the hand's ability to grip. If long folds in the surface of the finger give water a channel through which to move, the pressure of the grip will push the water outwards and let it drain away. Looked at this way, a wrinkly hand is the body's way of saying that you've been in the water too long and you clearly need help getting out.
This idea is not universally accepted, but it might explain why there is one permanent way to stop fingers from wrinkling in water. When the nerves to a finger or hand are severed, the wrinkling reaction stops. Scientists figured that out in the 1930s, but couldn't explain why. Perhaps this is the reason. Your hand doesn't know you're in trouble, and so it doesn't re-configure itself trying to help you onto dry land.
Via Scientific American.