With credit to Science....
Long thought to be caused by osmosis-induced swelling in the outer layer of skin, the wrinkles are in fact produced by the autonomic nervous system, recent experiments indicate. But the purpose of the puckering—which occurs on hair-free skin of the hands, feet, and toes but nowhere else on the body—hasn't been clear, says Tom Smulders, an evolutionary biologist at Newcastle University in the United Kingdom.
In 2011, a team of neuroscientists suggested that the wrinkles served to enhance our grip on wet or submerged objects, just as treads on tires help improve traction on wet roads. "That seemed like a clever hypothesis that would be easy to test," Smulders says.
So he and his colleagues designed a test in which volunteers picked up 45 submerged objects—such as glass marbles and lead fishing weights—from a bin one at a time, passed them to their other hand through a postage stamp–sized hole in a barrier, and then dropped them through another hole into a box. When test subjects had wrinkly fingertips—induced by soaking their hands in 40°C water for 30 minutes—they completed the task about 12% faster than they did when their fingers hadn't been soaked, the team reported on 8 January in Biology Letters. When performing the same task with dry objects, wrinkly fingertips didn't provide an advantage.