Purpose of fingerprints

[Sphairon]

Hello,

one question has been pressing me for quite a while:

What's the evolutionary purpose of fingerprints?

According to Wikipedia, a number of primates, koalas and fishers also enjoy this feature, but what is it actually good for? Why not just leave fingers and hands blank instead of creating such a fascinating pattern?

Thanks in advance for your contributions.

[mith]

increased grip?

[Darby]

One would assume they produce better surface touch sensation - lateral movement of the ridges should pick up more than a smoother surface.