Cab­i­net of Won­ders pro­vides us with every­thing you’ve ever wanted to know about fin­ger­prints, but were afraid to ask. I par­tic­u­larly enjoyed this tidbit:

Spi­der mon­keys, whose pre­hen­sile tail-tips are so sen­si­tive and flex­i­ble that they can pick a dime up off a floor, also have prints on the bare spot at the end of their tails. Since the tails are used not only as a sort of third arm when swing­ing in the trees (as a safe­guard from falling), but often sup­ports the entire weight of their bod­ies while they feed, this would make sense: fin­ger­prints, and other places with “fric­tion ridges” — the volar regions — gen­er­ally tend to occur where one needs to grip some­thing. This can mean grip­ping an object to keep from drop­ping it, or (as in the case of trees) to keep it from drop­ping you, or sim­ply to keep your feet steady on the rocks so you don’t fall off a cliff.

But how does it work?

via Seed