Finally, an explanation for why our fingers and toes get all pruny when they're wet

Illustration for article titled emFinally/em, an explanation for why our fingers and toes get all pruny when theyre wet

Shriveled fingers and toes are something we're all familiar with, yet scientists have struggled to explain why it happens. A longstanding theory is that wrinkles are the result of water passing through the outer layer of the skin, causing it to swell. But as neuroscientist Mark Changizi pointed out a few years ago, it's clearly a spontaneous reflex that requires a better explanation. Now, writing in Biology Letters, researcher Tom Smulders believes he's found the answer — and it has to do with our ability to handle wet objects.


Smulders, who works at Newcastle's Centre for Behaviour and Evolution, has confirmed that objects are indeed easier to handle with wrinkled fingers than with dry, smooth ones — a suggestion that our ancestors evolved the physiological response as they foraged for food in wet vegetation or in streams. While Changizi proposed a similar theory, it was Smulders who proved him correct by virtue of a simple experiment. Writing in BBC, Jonathan Amos explains:

[The study] involved asking volunteers to pick up marbles immersed in a bucket of water with one hand and then passing them through a small slot to be deposited by the other hand in a second container.

Volunteers with wrinkled fingers routinely completed the task faster than their smooth-skinned counterparts.

The team found there was no advantage from ridged fingers when moving dry objects. This suggests that the wrinkles serve the specific function of improving our grip on objects under water or when dealing with wet surfaces in general.


Makes sense. Pruny toes would have certainly helped when walking on slick, wet surfaces.

Smulders contends that the response, which is triggered by the nervous system under strict conditions, has to have an underlying reason for it — which he says is the result of natural selection.

The next step for the researchers will be study how wrinkled fingers are able to improve grip and remove excess water, a process that may be similar to how wet tires work.

More at BBC.

Image: Taratorki/Shutterstock.


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Curious, does anyone know if apes' fingers get pruny?