I'm glad you elaborated on the original post's mention of fingerprints because that caught my attention too! It is cool to learn to the evolutionary advantage (grasping leaves easier).

In one of my anatomy classes, my teacher told us that fingerprints are formed when a developing fetus rubs the developing fingers against the wall of the uterus. The random rubbing patterns create grooves in the skin, as the skin grows. I can't site a source here because my teacher told us that in class. I haven't looked it up to fact-check since, but I'm sure it holds some weight!