This story reminds me a lot of one from a few weeks ago. Someone wrote a clever rebuttal to a ridiculous article suggesting that the reason why women go through menopause is that men like to have sex with young women. The rebuttal pointed out that there are other, much better, theories to explain the phenomenon.
One of those theories is the grandmother theory. Basically, having your grandmother around when you are a baby makes you substantially better off and more likely to survive. Thus, those with longer-lived parents were more likely to have more offspring.
I feel like a lot of the thinking this article highlights commits the same fallacy as the sex-with-young-women hypothesis article. We assume that sex with more partners should be favoured because it makes it more likely that the male has more children. But there is more to reproduction than spreading your seed as widely as possible (in our species anyway). In order to be successful in evolution, you need not only to have your children be conceived, but also be born, grow up, and have children of their own. There are a lot more factors to evolutionary success for males than just getting the gametes out there.
With that in mind, it is not hard to come up with a hypothesis about why monogamy came about; having a father around was presumably very helpful to survival (I recognize the article mentioned this, but I didnât think it got nearly the billing it deserved). On top of that, society is a lot more likely to survive when everyone has prospects of finding a partner. If a few rich men get to marry all the women then you are going to end up with a generation of very angry and very dangerous young men.
Lastly, when it comes to evolutionary success, the ultimate weapon for a species is not size or strength, it is diversity. Having everyone pair off each generation maximizes the diversity of the next generation. In the very short run having the strongest man mate with all the women will produce stronger children, but eventually that strategy is going to leave you more vulnerable to real species killers like disease.
