Why do your fingers and toes wrinkle during a bath?

Most people think that it is due to water entering the surface cells of the skin on the fingers and toes, causing it to swell up and therefore wrinkling. But a group of scientists have discovered that it is in fact an involuntary action brought about by the autonomic nervous system, which also controls our rate of breathing and heart rate. This finding was made based on the observation that this effect does not occur in people with nerve damage in their fingers.

It has been suggested by a group of evolutionary neurobiologists that wrinkling, being an active process, must have an evolutionary function. The team showed that the pattern of wrinkling that occurs appears to be optimized for providing a drainage network that improved grip on objects when the skin is wet. It could also be analogous to how the treads on car tires work; which allows a greater surface area to be in contact with the road so as to offer better grip under wet conditions.

In the latest study by the team, whose data was published in Biology Letters, participants picked up wet or dry objects with normal hands or with fingers wrinkled after soaking in warm water for 30 minutes. The subjects were faster at picking up wet objects with wrinkled fingers than with dry ones, but wrinkles made no difference for moving dry objects. 

The team suggested that the increased surface area resulting from the wrinkling might have helped our ancestors in gathering food from wet vegetation or streams. The same effect on our toes might have contributed to a better footing while walking on wet rocks.

Cheers to one more trait that made us survivors!

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