In modern times, you see most men having short hair and most women having longer hair. However, it seems like something like that is more of a product of society instead of something like genetics, so that led me to wonder about this question. I hope this isn't more of a science question rather than a history question.
Edit: Question should be "At what point did having longer hair become more of a feminine trait?"
As an extension to the question, have women always worn their hair long, or have there been societies where short hair on women was the norm?
Would head lice and conscription have played a role in men adopting shorter hair?
I'd always been told that is why most modern militaries short crop the hair of all recruit and make them keep their hair short.
It's really hard to say, as they wasn't ever really a full norm in history, like there isn't really now. Maybe it is in a euro centric view, but even then...vikings for example, everyone knows those guys..well, they weren't unified for a long time and were comprised of little jarl lead clans. In some clans, it was common to have long hair as a man, in another you might have thr more typical reverse friar look (where you shave around the middle instead of shaving the middle).