system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do men, traditionally, have short hair and women have long hair?
gpt
A lot of it has to do with the military requirements of WWI. This is also why the male standard is to be clean shaven. Prior to WWI long hair was common on men, as were beards. The military required short hair to limit  liability in hand to hand combat, and required you to be clean shaven for the better fit of a gas mask.