When did the presumption that men should have short hair and women should have long hair come about??

While you wait for an answer, you may be interested in these previous answers on the subject:

From 2 years ago, by /u/chocolatepot
From 4 years ago, by /u/Serae
And from 7 years ago, by /u/nhnhnh

For the mods, it might be worthwhile to note that many of the links in the FAQ have top comments which simply redirect to the FAQ or deadlink to other parts of the subreddit. The section could use some cleanup and reorganization.