Why wrinkle in water

But whether and how the wet-wrinkling response may have evolved, and if it even represents an adaptation in the first place, remains a contentious debate. Consider tyre treads. In dry conditions, smooth tyres can best maintain their grip on the asphalt, which explains why race cars typically have smooth, featureless tires. But when driving in rain, treads are far safer. Wrinkled fingers, then, could be optimally designed for gripping in both wet and dry conditions. But researchers can look for hints, tell-tale clues that indicate that a feature may indeed have evolved as an adaptation.

In , Changizi and his colleagues found evidence that wrinkled fingers indeed act as rain treads, channelling water away from the fingers and toes during wet conditions, allowing primates — humans and macaques, to be specific — to maintain tighter grips. In other words, the wrinkles that result from exposure to water can be thought of as tiny, manual river drainage systems. The pieces of land between the streams and brooks, on the other hand, are disconnected.

To see if wrinkled primate fingers had similar features to river basins, Changizi and his team analysed photos of 28 human fingers. Credit: Getty Images. The results were fascinating: the subjects with wet, wrinkled fingers were able to pick up the marbles much faster than those with dry hands. Furthermore, it takes significantly less time to wrinkle in freshwater than it does in seawater. Well, it goes back to osmosis. When you are in a pool, the salt concentrations of H2O in your skin are higher and so the water from outside goes in.

Well, when in the ocean, the salt content in the seawater is much higher and therefore draws the water in your skin, after the sebum has rubbed off, out into the ocean. Can you imagine? But this isn't the first theory proposed to explain finger wrinkling—and it may not be the last.

Dealing with joint pain can cause major disruptions to your day. Sign up and learn how to better take care of your body. Click below and just hit send! Are wet-induced wrinkled fingers primate rain treads? Brain Behav Evol. Wilder-Smith EP. Water immersion wrinkling--physiology and use as an indicator of sympathetic function. Clin Auton Res.

Ann Biomed Eng. Water-induced finger wrinkles do not affect touch acuity or dexterity in handling wet objects. PLoS One. Published Jan 8. McCorry LK. Physiology of the autonomic nervous system. Am J Pharm Educ. Water-induced finger wrinkles improve handling of wet objects. Biol Lett. The results are published today in Biology Letters. Hold tight Wrinkled fingers could have helped our ancestors to gather food from wet vegetation or streams, Smulders adds.

The analogous effect in the toes could help us to get a better footing in the rain. Changizi says that the results provide behavioral evidence "that pruney fingers are rain treads", which are consistent with his own team's morphological findings.

What remains to be done, he adds, is to check that similar wrinkling occurs in other animals for which it would provide the same advantages. Given that wrinkles confer an advantage with wet objects but apparently no disadvantage with dry ones, it's not clear why our fingers are not permanently wrinkled, says Smulders. But he has some ideas.

This article is reproduced with permission from the magazine Nature.