I read that the curly / straight nature of hair was due to its radius and the shape of its cross section. If it is circular, then the hair is straight, if it is oval in cross section, it is weaker on one axis and bends easier, and forms curls. Thick hair might be straighter. (I believe Oriental hair has thicker fibres, which is why it tends to be less curly than whispy north european hair).
The actual purpose of pubes - i.e. why we still have them - is also interesting. Is it for display, camouflage, protection, a wick, for scent?
As far as I can see it is 'neither use nor ornament' to quote a northern expression.
I don't have a problem with armpits, though; where did our society get that one from? A 'youth' thing, perhaps.