Why do fingers wrinkle in water?

Stay in the bath too long and your fingertips turn wrinkly. For years people thought the skin was simply soaking up water and swelling. That is not the whole story.

The wrinkles are made by your nerves. When your fingers sense they have been wet for a while, the nerves tell the tiny blood vessels under the skin to shrink. The skin above loses volume and folds into wrinkles.

Why would the body do this on purpose? Experiments show that wrinkled fingers grip wet objects better — like the treads on a car tyre pushing water out of the way. Our ancestors may have used them to pick up food in rivers or walk on wet rocks.

People with nerve damage in a finger do not get wrinkles on that finger, which proves the nerves, not the water, are in charge.