It's not just inequality between males, but also the wellness of poor people.

If people worry less about starvation, they will put less emphasis on potential partner's financial status.

That doesn't explain polygamy in the richer parts of the Middle East where it's far more common than Western Europe. Starvation or even significant malnourishment beyond ones own poor choices aren't common. Relative economic inequality is common though to both places.

> Economic inequality between males means more and more women are competing for a smaller supply of wealthy males. Increased demand for top males leads to gender inequality as more and more women compete for a smaller pool of rich men, reducing the bargaining power of every individual woman and increasing the bargaining power of the few males who are marriage material.

I don't see how any of this holds up in today's society where women are earning just as much as men, and in some relationships, more.

A woman making 10K and a woman making 100K will both face social pressure against dating a guy making 80% of what they do, since the pressure is about the relevant income and not the total income. So this means that the more women make, the bigger this problem becomes because it drives up what is considered a rich enough guy, even if there wasn't the other problem of the wealth gap growing.

Rape is illegal. Since males can't force females to procreate, female choice is the deciding agent in determining who mates with who. Females choose mates based on their genetic fitness and their ability to provide resources. Genetic fitness is determined by all of: a male's ability to acquire resources (wealth), his looks (square jaw), talents (guitar player), personality (funny), social status (fame/popularity).

If a female no longer requires resource provision because she is earning enough money, she will prioritize genetic fitness in her mate selection, and so will be MORE willing to engage in a polygamous arrangement because polygamy can get her access to a greater diversity and quality of genetic material. Monogamy is only necessary for the female if it will provide her with resources or protection. Monogamy is not necessary for her to get access to sperm--sperm is cheap. She doesn't worry about money and can instead get the best genetic material without the best resources.

Therefore, female wealth drives polygamy.

But male economic inequality also drives polygamy.

Both factors increase polygamy. The only way to reverse these pressures would be to legalize rape and return to a state of nature. This would dethrone female agency as the factor that determines who will reproduce with who, and would elevate male violence to the deciding factor.

"I don't see how any of this holds up in today's society where women are earning just as much as men, and in some relationships, more."

A lot of this study isn't about "today's society". Also notice the last paragraph: "Monogamous marriage has largely preceded democracy and voting rights for women in the nations where it has been institutionalized, says Henrich, the Canadian Research Chair in Culture, Cognition and Evolution in UBC’s Depts. of Psychology and Economics. By decreasing competition for younger and younger brides, monogamous marriage increases the age of first marriage for females, decreases the spousal age gap and elevates female influence in household decisions which decreases total fertility and increases gender equality."

The best recipe for monogamy is clear:

* Keep rape illegal

* Reduce male economic inequality

* Reduce female personal wealth

Since rape would still be illegal, female desire would still be the agent that determines reproduction and mating. But since females have no personal property, they would have to acquire resources by accessing a male's resources. Since males are all roughly equal, she will prefer to find a male who does not provide resources to other females.

Voila! Monogamy.

This assumes the females are completely dependent on the wealth of the males and I think this is less common than it has been in the past. Take the economic dependency out of the equation and female choice is much broader.

I think also, if wealth was the most important factor wouldn't it make sense for one female to have multiple male partners contributing? That would reduce the need to compete for 1 economically strong partner.