Christoph Niemann

THE FACTS

Anyone who has ever been out in the rain too long or soaked for hours in a tub knows the prunelike effect it can have on your hands and feet. Conventional wisdom suggests it is nothing more than the skin absorbing water.

But a number of questions have puzzled scientists. Why do “wet wrinkles” appear only on the hands and feet? And why are the most prominent wrinkles at the ends of the digits? Surgeons already know that cutting nerves in a finger prevents the wrinkling, suggesting the process is controlled by the nervous system.

Now a paper in the journal Brain, Behavior and Evolution offers more evidence that wet wrinkles serve a purpose. Much like the tread on a tire, they improve traction.

In the study, an evolutionary neurobiologist and his co-authors examined 28 fingers wrinkled by water. They found that they all had the same pattern of unconnected channels diverging away from one another as they got more distant from the fingertips.

The wrinkles allow water to drain away as fingertips are pressed to wet surfaces, creating more contact and a better grip. Next is a plan to study whether pruney fingers are in fact better at gripping, and whether mammals in wet habitats are more likely to get them. Wet wrinkles have been confirmed only in humans and macaques.

THE BOTTOM LINE

Wet wrinkling may serve a purpose: better grip and traction.