(Not so) slippery when wet

“What,” exclaims our increasingly despairing editor “…happened here?”

Despite the Science Lite desk’s attempts to cover the rapidly expanding puddle of water at our feet, the sodden patch darkens and gives us up. Having just returned from our daily doughnut run to Greggs we became caught in a downpour that would make even Noah a little nervous. The deluge was now dripping from our damp figures and embedding itself deep in the generically blue office carpet.

Crestfallen as flood-damaged doughnuts are disposed of, we realise they are not the only victims. Our finger tips have taken the form of wrinkled mollusks – puckered and pallid eminences, looking for all the world like the foot of a recently de-housed limpet. Which got us thinking – why on earth do fingers prune when wet? Surely it must just be a biological accident? Well, not so according to research from Newcastle University. Believe it or not it looks as though the ability to wrinkle is a trait that, in the great talent contest of nature, has been deemed useful.

Dr Tom Smulders from Newcastle’s Centre for Behaviour and Evolution has found that wet objects are easier to handle with wrinkled fingers than with dry, smooth ones. By clever use of marbles, a bucket of water and some keen volunteers, Dr Smulders was able to show that wrinkled fingers routinely can pick up and manipulate marbles immersed in a bucket of water faster than their smooth-skinned counterparts. That’s all well and good, but this finding only becomes truly wonderful when considered with some other evidence – evidence that is nearly 80 years old.

In 1935 clinicians were studying patients with palsy of the median nerve when they discovered that skin wrinkling did not occur in the areas of the patients’ skin normally innervated by the damaged nerve. This suggested that the nervous system plays an essential role in wrinkling, so the phenomenon could not be entirely explained – as previously assumed – simply by water absorption. So, it seems clear there is complexity at play here. Indeed recent investigations have actually shown the furrows to be caused by the blood vessels constricting in reaction to the water, which in turn is a response controlled by the body’s sympathetic nervous system.

It is not hard to imagine the evolutionary advantage this may have given our forebears – with food foraging along the shore line or river bed being decidedly easier with the odd digit-wrinkle. A slight advantage maybe – but evolution, quick to pounce on even the merest of footholds, would have worked this trait to furrowed perfection. So next time you spend a little too long in the bath – glance at your be-pruned fingers and revel in the relative ease with which you pick out the soap.

Thank you evolution.