Stick your fingers in water and your fingertips will soon start to wrinkle. There’s a common belief that this happens because the tips absorb water, but that can’t be right. Since the 1930s, we’ve known that the wrinkling process is under nervous control—if you sever the nerves in your finger (don’t try this at home, kids), the wrinkles won’t form.

But neurobiologist Mark Changizi has an intriguing hypothesis about the origin of pruney fingers—they’re an adaptation that allows us to grip wet surfaces. Like the rain treads on tyres, when pressed down, pruney fingers create channels that let water drain away, allowing them to make better contact with damp surfaces.

The new study has picked up a lot of coverage,