Polygyny is widespread across many human societies….
Yet in much of the world, particularly the wealthier parts, monogamy — albeit with cheating around the edges — has flourished. Why? The article says the answer lies in the “group selection” advantages conferred by the one-wife norm, which reduces the pool of men who can’t find any wife at all, making them less likely to become socially alienated and violent. And the practice helps the elite, too: “By shifting male efforts from seeking wives to paternal investment, normative monogamy increases savings, child investment and economic productivity.”
It is important to note that:
The authors stress that it is not only monogamy that causes cultures to flourish but any “polygyny-inhibiting” cultural practices. That would include Islam’s restrictions on the number of wives men can take (four, the authors say).
In conclusion the authors note that:
it is worth speculating that the spread of normative monogamy, which represents a form of egalitarianism, may have helped create the conditions for the emergence of democracy and political equality at all levels of government. Within the anthropological record, there is a statistical linkage between democratic institutions and normative monogamy. Pushing this point, these authors argue that dissipating the pool of unmarried males weakens despots, as it reduces their ability to find soldiers or henchman.
The entire paper (click here) has more nuance than this summary depicts. You may not agree with all the implications of the findings (I for one remain dubious, I couldn’t help but suspect potentially serious cases of omitted variable bias), but it is definitely worth a read.
HT WSJ Blog here.