Monogamy & Polygamy
Polygamy is currently illegal in the U.S. and most other nations. But it has been practiced in most human societies. Should it be legal? And, whether or not it’s legal, is it a good thing?
I think the answer is (a) it should be legal, (b) it is good for some people, but (c) it is bad for society.
I. Background
In some sense, polygamy is more natural than monogamy. Traditionally, around 85% of human cultures have practiced at least occasional polygamy (this is based on the Ethnographic Code Atlas). Most people probably don’t realize that, though, because monogamous societies have grown and spread so much more than the polygamous societies, and most modern nations prohibit polygamy.
Of the societies that practice polygamy, almost all of them practice polygyny (where a man can have multiple wives); very few practice polyandry (where a woman may have multiple husbands).
II. Legality
My argument for legalization is the simple libertarian argument. Marrying more than one spouse, with the informed consent of all parties, is not a rights-violation. It doesn’t violate the rights of any of the people involved in the marriage, because informed consent in general prevents an action from violating rights. It doesn’t violate the rights of anyone else, because people don’t own other people; hence, third parties don’t have rights over whom you marry or who marries you.
Prima facie, it’s wrong to forcibly interfere with people who are not violating anyone’s rights; hence, it’s prima facie wrong for the state to interfere with polygamous relationships. Obviously, this applies to polyandry just as much as polygyny.
III. Is Polygamy Good for Us?
I think some people are under the impression that polygamy is bad for women, that it’s a tool for men to exploit and oppress women, etc. Of course, coerced marriage (as has existed in many societies) would be a form of oppression and exploitation. But as long as, again, you have informed consent from everyone, there’s nothing particularly exploitative or oppressive, and one should expect that most people who got into polygamous marriages to be benefitted by it, including both men and women.
It’s obvious how polygamy would be good for some men, those who obtained multiple wives. They would presumably satisfy their desire for multiple women. (They might be able to do that within a monogamous marriage, by cheating, but this is in various ways much worse.) Women who wanted multiple husbands would be similarly benefitted.
What about people who don’t want to share a spouse? Well, legalizing polygamy wouldn’t make it mandatory; people who wanted monogamous marriages could still do it. They could sign monogamous marriage contracts that prohibit each other from taking additional spouses.
Suppose some very desirable person gets multiple spouses. Say, Brad Pitt gets 10 wives. One of those spouses would plausibly be worse off as a result of the legality of polygamy, namely, the one whom he would have married if polygamy were illegal. But the other nine are better off, because they get to marry Brad Pitt. Since they gave informed consent to marry him (we’re assuming), they preferred sharing him over whatever alternatives they would have had (presumably, having some much less desirable man). This is pretty good prima facie evidence that they’re made better off.
The same reasoning applies to the husbands if a very desirable woman takes multiple husbands.
IV. How Would it Work Out?
Now, everyone should know what would in fact happen if polygamy were legal and socially accepted in our society. But while everyone should know this, a lot of people don’t, because they are in denial. So I’ll tell you what would happen.
First, a significant number of men – those at the top of the attractiveness scale (and here I’m including not just looks but social status, cleverness, wealth, and anything else that might make one desirable) – would wind up with multiple wives. A much smaller number of women would take multiple husbands.
Why would this happen? Two reasons. First, men have much stronger desire for sexual variety than women. Second (relatedly), there are a lot fewer attractive men than there are attractive women. These graphs are based on data from OkCupid:
What this means is basically that most men find most women attractive; but most women find most men unattractive. Note how the mode for female attractiveness is in the middle, whereas the mode for male attractiveness is at the bottom of the scale.
Btw, we know from evolutionary psychology why this is the case. In our evolutionary past, men maximized their reproductive success by mating with as many women as possible. Women maximized their reproductive success by mating with a ‘high quality’ man.
So what would likely happen in a polygamous world is that the small number of men who are attractive would take multiple wives. The great majority of women would wind up married. The small number of women who are unattractive might remain unmarried, or marry unattractive men. Then there would be a large number of unattractive men who would remain single (even more than at present).
If you find this surprising, or you feel reluctant to accept it, you really shouldn’t. Again, anthropologists have found polygyny much more common than polyandry in human societies. In addition, DNA studies show that the current generation of humans has about twice as many female ancestors as male ancestors (https://academic.oup.com/mbe/article/21/11/2047/1147770). The best explanation for this is, again, polygyny. Historically, most females reproduced, and most males did not. If we changed our laws and customs to let people do whatever they want, it would be totally unsurprising that people would revert to the natural pattern followed by our ancestors.
V. Consequences
Now, here’s why all this would be terrible for society. Initially, when we introduced polygamy into our society, it would be good for almost all women and a few men. It would be terrible for most men, who would be unable to find a partner.
What would happen to those men? First, most of them would be very unhappy for pretty much their entire adult lives. Some of these men would commit suicide (men, by the way, already have much higher rates of suicide than women). Others would become criminals (even more than at present; marriage reduces one’s tendency to commit crime).
This is no exaggeration. If you find this odd, think about it in evolutionary psychology terms, again. Evolution selects for reproductive success. That’s a higher priority, for evolution, than anything else, including survival.
Anecdote: Think about the female praying mantis, who sometimes eats the male right after mating. Why do the males risk this by mating with females? Because natural selection favors those who reproduce, not those who live a long time without reproducing.
So for the men who can’t find a mate, many would feel as though they have nothing to lose. I don’t have any estimate of how much the suicide and crime rates would increase, but I think it would be significant.
To return to the point I mentioned at the beginning: Isn’t it interesting that, although the vast majority of human cultures have accepted polygamy, it is illegal in the great majority of modern countries? Why is that?
One explanation is a kind of evolutionary process for cultures: Societies that practice polygamy are less successful as societies than those that practice monogamy. This could be for the reason cited above: they have a large portion of their society who are unhappy and feel as though they have nothing to lose. So the monogamous societies spread and grew richer and more powerful.
Aside: You might find it surprising that the 'natural' behavior for humans would be maladaptive in this sense. But it's really not so strange. What biological evolution selects for is not the success of a society, but the success of the individual gene (i.e., genes that promote their own reproduction are expected to predominate, even if they harm the society that they exist within). There are many traits that increase one's own reproductive success at the expense of society; taking multiple wives is one of them.
Here’s a graphic from Wikipedia showing where polygamy is allowed:
The places where polygamy is legal are generally among the least prosperous societies (esp. those in Africa and the Middle East; this is partly due to the influence of Islam).
VI. What to Do?
Perhaps the legalization of prostitution would reduce the negative impacts of polygamy. Men might feel okay as long as they have sexual partners, even if they have to pay for it (in our evolutionary past, there was not effective contraception, so evolution designed men to highly value sex, even if there in fact won’t be any offspring since the woman is using contraception).
This would still leave many men without other advantages of marriage – without a life partner, without companionship when they grow old, and so on.
Perhaps what we should have is a strong social convention against polygyny (as we currently have), but without legal penalties. There’s no reason to oppose polyandry, though, so society should tolerate or even encourage that. This is the reverse of what most human societies have done, because most human societies are lame, and their conventions were designed more for the pleasure of the rulers than for the good of the society as a whole.