James Hamblin, M.D. wonders why we get prune fingers when our hands get wet:

The wrinkles channel water off of our fingers, so we get better traction on things we want to hold.

Yes, someone did a study:

This week, research in the journal Biology Letters, proved that people with water-wrinkled fingers were indeed faster at picking up wet marbles.

So, as evolution would have it, our ancestors who were not as good at picking up marbles were less likely to be chosen as suitable mates and pass along their genes. Or, actually, the ones who weren’t as good at hand fishing and clam digging and those sorts of things after their hands were all wet and slippery; they wouldn’t thrive and reproduce. The prune-fingered people, meanwhile, flourished and feasted and were the eminently desirable.

What about prune toes?  Read more from Hamblin’s article in The Atlantic here.

Abstract from Biology Letters here.