Spend some time in a pool, lake, or other watery location, and it won’t take long to see deep ridges of wrinkles spreading across the pads of your fingers and toes. Despite often earning the unflattering adjective “pruney,” these wrinkles disappear in about 20 minutes once back on land. At first glance, these H2O-induced crevices seem like a simple case of osmosis, in which water floods membranes (in this case our skin) to equalize on both sides. But then why doesn’t the rest of the human body wrinkle when submerged in water?
Human hands and feet are very similar in some ways — but they don’t have the same number of bones. The foot contains 26 bones, while the hand has 27. The pisiform, the extra bone on the outside of the wrist, serves as an attachment for tendons and ligaments.
Today, we know this wrinkling is caused by constriction of the blood vessels (which is also why fingers and toes turn pale at the same time). The leading theory as to why this happens is that our hands evolved to wrinkle in wet environments to improve grip, whether we’re running in a rainstorm or grasping a potential meal in a freshwater stream. Several studies, including one published by Manchester Metropolitan University in 2021, found that grip improved dramatically when hands were especially wrinkly after water submersion. Humans also aren’t the only ones with this skin-morphing ability. The Japanese macaque (Macaca fuscata) is known to take long baths in hot springs, and it has wrinkled hands to prove it. Scientists are still debating the true nature of this involuntary skin response, but at least now you can look upon your deeply creased digits with a new respect — even if they are “pruney.”
Media Release/Interesting Facts
