I’m betting on monogamy since that has worked for thousands of years.
Not all societies today even value monogamy. In France some consider the President weak if he doesn't have at least one mistress. And in fact the same thing in America.
Let's be honest you're trying to use a nature to excuse behavior most find unacceptable - there's risk residue if Christianity in that. I see this a lot in these appeals - you're essentially arguing that if you can show someone thing is natural it's beyond question. However, anthropologists admit that most human societies have developed monogamy of one form or another, with exceptions only for rulers.
The reply asked worked for who? Then out of nowhere you're talking about men being killed in droves. Are you saying that monogamy didn't work for either gender (one that lost their freedom and and the other that lost their lives)?
Theirs is a borderline flame bait comment that added nothing to the discussion.
Not by women. Obviously it's not that simple, but that is a true statement.
Also, do you believe women would not be competing for resources if there were no men, and are not competing for resources in general?
We're not out here trying to convince men that being able to have sex with multiple partners throughout their lives is a good idea -- that part comes naturally to us.