The harems are already here. The most attractive individuals among both men and women get a lot of attention from people attracted to them, and thus have their harems and can sleep around a lot (if they want to).

Say the "successful on Tinder" group of 5%-er men who go to the gym nonstop, and have won the genetic lottery. There is also the "influencer" group of women with countless thirsty men in their DMs. Not every woman manages to become an influencer, but many are extremely beautiful.

Are people in these harems happier being delulu than in some monogamic relationship? I'm not really sure.

Industrialized society has managed to deliver lots of high quality products by replacing the human component with machines... relationships are something entirely between humans however, so they are hard to improve with industrialized processes. Until robotic girlfriends/boyfriends arrive of course :).

Women have strong biological incentives to have fewer partners, even with birth control - they are far more susceptible to sexually transmitted diseases, for one, as well as violence, and more partners means more risk of any one partner being a problem on that front. And all it takes is one.

If resources are constrained, it’s a toss up if it’s better to have one dedicated partner with a strong bond, or multiple partners with weaker bonds. Depends I imagine on a lot of other dynamics, and if there are kids involved.

There certainly are dynamics where many weaker bonded partners is worth the risk, or prostitution wouldn’t be the world’s oldest profession.

It's not loser need sex.

It's loser need marriage.

Somehow I think we've found the sticking point.

>I haven't seen any convincing arguments that it does in humans.

Then you have not made a sincere attempt to date multiple partners as a man in the bottom 60%.