A question I've pondered over recent years, has been why men in so many cultures gave up the right and tradition to have multiple wives? Historically, polygyny has been one of the most common and prevalent forms of marriage, worldwide. But, in modern Western culture, men with multiple wives are seen as sinners and lawbreakers.
This flies in the face of increasing evidence that for many men (though not all), there are genetic, biological and psychological factors that dispose them to not be monogamous. As my colleague Eric Anderson argues in his new well-researched book, The Monogamy Gap, there is increasing evidence that monogamy is not a natural state for males, a dilemma which contributes to high rates of pornography use, infidelity, and marital difficulties. Anderson makes a clever point, suggesting that infidelity actually is a "part" of monogamy, asserting that for such men, sexual infidelity is a way to stay monogamous to a single partner. Remember that monogamy as a term does not describe sexual fidelity, but merely the act of marriage to a single person. In our current usage, we blur the concepts though, especially in the world we live in, where sexual fidelity is seen as the ultimate expression of love and commitment.
So, as I've seen this rising evidence that demanding sexual fidelity of men is challenging, to say the least, I've wondered why and how it is that societies came to adopt monogamy (meaning sexual fidelity to a single person, and men having only one wife). If Western culture and American society really have been dominated by patriarchal control (I'm not so sure this as true as we think; Baumeister's book Is There Anything Good About Men is a delightful challenge to this assumption), why would these men in charge give up the right to have multiple wives?
And now, here's the answer. In "The puzzle of monogamous marriage" (see, I wasn't the only one puzzled by this) by Henrich, Boyd and Richerson, the authors present evidence that monogamy actually has significant social benefits. In polygyny, powerful men gather the most desirable women for themselves. And less powerful men "go hungry," wifeless. In fact, throughout human history, while 80% of women have reproduced, only 40% of men have. Those men who couldn't compete, didn't get to have even a single wife, and thus didn't have children. So, what did those men do with their time? According to Henrich, Boyd and Richerson, it appears they got into lots of trouble. Societies where polygyny has been (and still is) practiced, have higher rates of violent crime, poverty, and other types of crime such as fraud. Apparently, if you can't get a wife, what's the point of following the rules?
In fact, other research shows that polygynous cultures also end up with men caring less about the needs of their children, contributing less overall to family subsistence needs, and placing higher value on male aggression.
So, through a (probably unconscious) social process, societies have gravitated towards emphasis and requirement of monogamous marriages, because it smoothes out some significant social problems. By "sharing" out the women amongst a society's men, and allowing all men a democratic chance to get married, men spend more time worrying about looking like good potential mates, and have less time and energy to break the rules and get in trouble.
But just because those men in charge of societies "decided" to give up the right to have multiple wives, they clearly didn't give up their interest in having sex with multiple women. The sex lives of leaders like Mao Zedong, Jack Kennedy, and Newt Gingrich, show that while these men may have imposed monogamy on other men (under Mao, infidelity was a punishable crime), they haven't been all that interested in following these rules themselves. It sounds like a case of "Do as I say, not as I do."