Why Do Fingers Wrinkle In Water?

I am sure that you have probably asked why fingers wrinkle in water. I know when I was a kid I asked my parents. I got told that "it is your fingers getting tired of being soaked in water". Even as a kid I wasn't entirely convinced that the answer I was given was correct.

Now I have found out that there are a couple of different theories as to how and why water wrinkles fingers. So let's have a look at two of the more popular theories and perhaps decide which one we think makes more sense.

Theory Number One: Water Absorption.

This theory is the more generally accepted one and looks at the ability of the outer layer of your skin to absorb water. The skin on your body is the thickest on your fingers, palms and feet. The outer layer of skin actually has a protein called Keratin in the form of fibrous filaments which weave in a complex structure with dead cells called corneocytes. This complex structure allows the skin to absorb a lot of water instead of just dissolving. As the skin cells swell the outer layer triples in size and buckles, forming the wrinkles that are so familiar to all of us.

Theory Number Two: Adaptive Evolution.

This theory is relatively new and is all about fingers wrinkling in water for the purpose of increasing our grip on wet and slippery objects. It is theorised that the deep wrinkles on a water soaked finger act as drainage channels to help increase grip on objects when wet. It is said that Primates developed this adaption to help with climbing wet trees. Fingers have been studies and it has been found that the wrinkles that run vertically and stem from the tip of the finger closely resemble drainage networks in mountain ranges. It is said that due to the structure of the wrinkles as a fingertip presses down the water flows along the channels and enables the skin of the finger to fully contact the surface.

Human Skin Anatomy Model

So what do you think the real answer is?

I am a firm believer in evolution and believe that it could be possible that in the past we may have used the wrinkling of our fingers to our advantage. Yet I can't see there being enough selective pressure put on our ancestors to enable something like wrinkly fingers evolve as a necessary feature. The way I see it a bit of extra forearm strength which enhances the gripping power of the hands would be a more likely contender in helping arboreal creatures keep a better grip. For natural selection to work in favour of wrinkly fingers all the ancestors that had non wrinkling fingers would need to be at a significant disadvantage and more likely to come to harm before reaching breeding age. To me something like extra gripping strength would have given a bigger advantage over extra traction, which would have over taken in a selective way and made the wrinkling fingers for traction redundant.

So that is my opinion on the evolution theory and I believe that the fact water is absorbed into our skin and buckles due to extra volume is most accurate and I don't think that our bodies adapted to have wet wrinkly fingers for the specific purpose of better grip in the wet.

The first theory is more of a how fingers go wrinkly in water and the second theory is more of a why they go wrinkly in water. I certainly agree with theory 1 and think theory 2 is theoretically possible but probably not very likely. What do you think?

Be sure to comment and let me know what you think of these two theories.

Understanding Skin Flip Chart

Source for Water Absorption: http://www.abc.net.au/science/articles/2012/08/20/3570437.htm
Source for Adaptive Evolution: http://www.pbs.org/newshour/rundown/2011/07/wrinkled-when-wet-accidental-or-adaptive.html