Biology has evolved for men to sleep with multiple women and for women to sleep with one man. Anything different goes against millions of years of evolution.

A man can spread his seed multiple times to multiple women, and historically/evolutionarily speaking, without consequence. A woman needs to be more deliberate because she has to carry the baby for 9 months and evolutionarily speaking, be the one to raise the child. Things get more interesting though, if you've ever read the book, "Sperm Wars". Women have evolved to want to get pregnant by the strong alpha male who may or may not make a poor father/provider, but will want to marry the beta male who will be faithful and a good provider. Obviously a man with a combination of these traits is ideal, but rare.

Obviously modern times have fucked up our natural biology and sociology because of birth control, abortions, family court being so biased towards women, child support, etc.

edit: because the downvoats are funny for speaking facts. Just because our biology is wired a certain way doesn't mean it's good for society. I absolutely believe in monogamy and marriage, but that requires a bit of going against male biology. You can't question that prior to civilization, the alpha male had children with multiple women. That's just the way we were wired. And still are. I haven't read the bible as in depth as I would like but I met a woman once who is as religious as they come and she told me the bible says that there are aspects of men and women that we have to consistently fight against. She told me men are naturally weak and must work to become strong and that women are naturally manipulative and must work to not be so (I can't verify this but I don't see why she would lie to me). There are certain aspects of our biology that we need to fight for the betterment of ourselves and society. But do not confuse this with the aspects of our natural biology that the liberal overlords want us to fight against that is not good for society.