Why fingers wrinkle in water

Health

Evolution may play part

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Why does the skin on your fingers wrinkle after spending a long time in water? Conventional wisdom has it that they wrinkle because the skin absorbs water.
However, Dr Mark Changizi, an evolutionary biologist at 2AI Labs in Boise, Idaho, has other ideas. He thinks that wrinkles act like the treads on a tyre, allowing humans to get a better grip in wet conditions, a feature that has evolved over time.
In the study, Dr Changizi and his team scrutinised 28 photographs of wrinkled fingers, minutely recording the patterns.
Researchers found that the wrinkles formed vertical channels starting at the finger tip, and diverging further down the finger.
According to Dr Changizi, pressing a finger tip down on a wet surface squeezes the water out from under the finger and through the channels. This allows the entire finger's skin to come into contact with the wet surface, giving a better grip.
Past research has shown that finger water wrinkles fail to develop if the nerves to the finger are severed, suggesting that the nervous system is also involved in the response.
The fact that wet wrinkles only develop on the fingers and feet, backs up the "rain tread hypothesis", the researchers wrote in the journal Brain, Behavior and Evolution.
Scientists are now planning further research to find out whether grasping mammals which live in wetter habitats are more likely to possess wrinkled fingers, and if they are indeed superior to non-wrinkled fingers in wet conditions.