Human finger tips do not become wrinkled because they absorb water. Skin is a fairly good barrier that keeps out most of the external water. If our fingers did absorb a significant amount of water after staying in the pool or bath for several minutes, then our fingers would swell to round, plump shapes, which is the opposite of wrinkling. The wrinkling is actually caused by a reduction of fluid inside the finger tips. Public Domain Image. Source: Christopher S. Baird. How can our finger tips experience reduced fluid internally when exposed to increased fluid externally? From a physical perspective, this effect seems to be a paradox. The answer is that the wrinkling of wet finger tips is an active biological response, rather than a passive physical effect. Scientists have known for almost a hundred years that nerve damage in the hand can result in a person no longer being able to get wet-induced finger wrinkles. Finger wrinkling is therefore controlled by the nervous system. Nerve signals cause blood vessels in the finger tips to constrict, reducing the amount of fluid in the finger tips. Just as drying out a grape causes it to turn into a wrinkled raisin, the reduction of fluid in the finger tips causes them to shrivel and wrinkle. Since finger wrinkling is an active neurological response, it is likely that evolution selected for it because this response confers some type of survival advantage. But how could wrinkles ever help one survive? This question has long been wondered and the answer is still far from settled. Many studies have been conducted by scientists all over the world which suggest that the improved-grip hypothesis is a possible explanation to wet-induced finger wrinkling. Source: wtamu.edu by Sir Christopher S Baird......