re: the notion that such a simple instrument couldn't evolve in different cultures without contact...

Drums are everywhere; some sort of strap to carry it when all the goatskin bags are full of [enter culturally-normal starch here] and it's not much of a leap for my imagination to see many people in many different places using what they have to fool around a bit more with their strap going thwank on the drum once they get where they're going.

CH.