When your fingers and toes get all wrinkly in the bathtub, it’s more than just a sign that’s it’s time to grab a towel. British researchers say it’s a trait primates acquired to give them better grip in the water, perhaps as they were swinging from wet branches, reports ScienceNews and the Telegraph. One theory is that the pruney skin acts sort of the way rain treads do on car tires. Researchers tested the theory by having people perform tasks such as moving marbles from a water-filled container to a dry one. Those who soaked their fingers beforehand to get them nice and wrinkly were 12% faster. The researchers speculate that having pruney fingers constantly would be a disadvantage, so evolution provided a way for early humans to have them only when necessary.