We've previously featured some of the creative ideas of evolutionary neurobiologist Mark Changizi, including his explanations for optical illusions, human blushing, and his notion that hospitals could use skin-colored gowns to track patient health.

Now Changizi is trying to explain why the surface of human fingers get pruney after prolonged exposure to the water. His hypothesis is that the marks help disperse water and improve grip:

Changizi thinks that the wrinkles act like rain treads on tyres. They create channels that allow water to drain away as we press our fingertips on to wet surfaces. This allows the fingers to make greater contact with a wet surface, giving them a better grip.[...]

When we press down with a finger, we apply pressure from the tip backwards. The sides of the finger are like cliffs where water can easily fall away, but the flat part is more like a plateau where water can pool. Wrinkles form on the plateau because "that's where all the work has to be done to channel the water away", Changizi explains.

Not everyone is gripped by the new theory. "This hypothesis is unjustified," says Xi Chen, a biomechanical engineer at Columbia University in New York. Chen thinks that the wrinkles have a simpler cause: when fingers are immersed in hot water, the blood vessels tighten and the tissue shrinks relative to the overlying skin. This contraction causes the skin to buckle. "It's a classic mechanics problem," he says.

Link -via Geekosystem | Photo: Ever So Strange