Wrinkled Fingers Are Better For Picking Up Wet Objects
January 10, 2013

Wrinkled Fingers And Toes Help Us Get A Grip

April Flowers for redOrbit.com - Your Universe Online

One of life's great pleasures is a long soak in a hot tub of water which often leads to wrinkly fingers and toes. A new study from Newcastle University suggests the reason for this wrinkling is to improve our grip on objects underwater.

"If wrinkled fingers were just the result of the skin swelling as it took up water, it could still have a function but it wouldn't need to," said Dr Tom Smulders, from Newcastle's Centre for Behavior and Evolution.

"Whereas, if the nervous system is actively controlling this behavior under some circumstances and not others, it seems less of a leap to assume there must be a function for it, and that evolution has selected it. And evolution wouldn't have selected it unless it conferred some sort of advantage," he told BBC News.

Smulders said, “We have shown that wrinkled fingers give a better grip in wet conditions — it could be working like treads on your car tires which allow more of the tire to be in contact with the road and gives you a better grip."

“Going back in time this wrinkling of our fingers in wet conditions could have helped with gathering food from wet vegetation or streams. And as we see the effect in our toes too, this may have been an advantage as it may have meant our ancestors were able to get a better footing in the rain.”

Wrinkling toes could have evolved as a way to efficiently run or walk on slippery ground, the Daily Mail reports.

Anytime our hands or feet are under water for a long time, they become wrinkled. It has long been thought that this was the result of water passing into the outer layer of the skin, making it swell up. It is now known, however, that it is an active process caused by blood vessels constricting below the skin. This reaction is controlled by the autonomic nervous system, which controls bodily processes such as breathing, heart rate and perspiration, reports Discovery News.

The wrinkling may have an important function, as it is an active process. It is only with this study, however, that scientists have been able to show that wrinkly fingers could offer an advantage.

The researchers studied people taking objects out of water with wrinkled fingers and again without wrinkled fingers to explain why such an effect occurs.

Participants picked up marbles of different sizes with normal hands or with wrinkled fingers after having soaked their hands in warm water for 30 minutes. The team found that people were faster with wet marbles if their fingers were wrinkled, but that wrinkles made no difference for moving dry objects. The study suggests that the winkles on fingers and toes serve the function of improving our grip on objects under water or maybe even wet objects in general.

Dr Smulders adds, “This raises the question of why we don´t have permanently wrinkled fingers and we´d like to examine this further. Our initial thoughts are that this could diminish the sensitivity in our fingertips or could increase the risk of damage through catching on objects.”

"We have tested the first prediction of the hypothesis - that handling should be improved," Dr Smulders said.

"What we haven't done yet is show why - to see if the wrinkles remove the water, or whether it's some other feature of those wrinkles such as a change in their stickiness or plasticity, or something else. The next thing will be to measure precisely what's happening at that interface between the objects and the fingers."

Dr. Smulders thinks it would be interesting to find out how many primates display this trait.

"If it's in many, many primates then my guess is that the original function might have been locomotion through wet vegetation or wet trees. Whereas, if it's just in humans that we see this then we might consider something much more specific, such as foraging in and along rivers and the like."

The findings of this study were published in a recent issue of Biology Letters.