system
A chat on subreddit /r/NoStupidQuestions
human
What's being kept "locked up" in that analogy? Female sexuality and reproduction. The reason it was kept "locked up" in the past was because, with property, money, and titles being passed down from father to son, men wanted to be able to ensure that their sons were really their sons. So women who slept with more than one man were demonized. Some cultures even thought that a man she had slept with years ago could be the father of or affect the appearance / behavior of a baby that she has years later. Men wanted virgins who wouldn't even look at another man their whole lives. 

But now we have paternity tests, less patriarchal inheritance laws, and less emphasis on bloodlines / blood relationships being necessary to have a family. So those old attitudes are no longer necessary. 

About it being easier for women to sleep around, I would say that sex is not some kind of prize or competition. People should be having sex because they want to have sex, not because it's some kind of accomplishment. Women want to have sex sometimes, and that's perfectly fine. It being easier or harder for some people to get sex shouldn't make it more or less socially acceptable for them to have it. 

Also with birth control now, sex is being separated from reproduction (when we want it to be). What once benefited us on an evolutionary scale (women being picky) does not serve the same purpose now. Being stuck in the past with old attitudes isn't something he should be proud of.
gpt
Nevermind the fact that lineage is easier to trace through mitochondrial DNA along maternal lines.