Question title says it all really. Polygamy is illegal in most US states, here in Britain and also no doubt many countries elsewhere, but why? What are the political motivators for this, especially in a country which has a separation of church and state?

  • Are you talking about the church marrying people, or the state doing it? Because in most countries the church can marry whomever they want for whatever reason they want, but the legal ones are restricted because they come with legal rights and benefits that could be abused and/or aren't designed for more than 2 people.
    – Erik
    Sep 23, 2017 at 20:43
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    Because in case of polygamy, majority of men will not be able to have any partners at all. This will probably cause some disappointment which will end up with an attempt to somehow get a partner which will end up with a violence. If you tell that every person can be married to at max 1 person, you ensure that majority of people will have a partner (no matter how unsuccessful they are) Sep 24, 2017 at 7:05
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    Just thought I should note the difference between polygamy, where you keep multiple wives in one house/family, and bigamy, where you either have wives in separate houses ignorant of each other or else marry someone without properly divorcing an earlier spouse. See Wikipedia for definitions. Most western countries prohibit both, although the iniquities of bigamy are probably more obvious (abandonment/financial support, inheritance, etc).
    – Stuart F
    Dec 11, 2018 at 17:36
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    @SalvadorDali: No, that does not follow. Polygamy would also allow a woman marrying multiple men, so the gender ratio of "available" people would not change.
    – sleske
    Dec 13, 2018 at 12:22
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    @sleske no, this does follow. Just because polygamy also allow for a woman to marry multiple men, this does not mean that the both cases happen equally likely. And based on historical data, it is way more likely for for a man to marry multiple women than other way around. If you want to show people the meaning of the words, you can also include that polygamy is not just about humans. It is the general concept. Dec 13, 2018 at 20:22

3 Answers 3


The main current purpose those laws serve is to placate a vast majority of the citizenry who object to polygamy (to the point of, about 100+ years ago, trying to physically destroy Mormons).

Ironically, this is as fully bipartisan issue as they come:

  • progressive feminists see polygyny (which is what most polyamorous relationships seem to be in history) as the ultimate expression of evil patriarchy (it's beyond the scope of the answer whether they are right or not)
  • right wing social conservatives see it as contradictory to mainline Christianity and New Testament rules (conveniently ignoring the whole King David, and especially king Solomon, precedents from Old Testament :) and generally a sexually deviant thing (it's beyond the scope of the answer whether they are right or not).
  • just to make this political bed-meeting weirder (and poly? :), the less-successful (or less full of themselves) people in MRA/etc... scene also object to polygyny, as it enables women to indulge in hypergamy even easier (it's beyond the scope of the answer whether they are right or not). The only time they see eye to eye with hard-core third wave feminists, I suppose. But stranger things happened.


Let's get down to the numbers. Even in these, extremely sexually liberal times, with polygamy being "morally acceptable" # as high as it's ever been in USA, only 17% population supports it, according to Gallup 2017 poll. That's up from only 7% in 2003.

If that seems "high" - compare it to 63%[1] supporting gay/lesbian sexual relations[2].

However, an argument may be made that those laws are in fact socially a good thing, in both theoretical and practical way:

In theory, in a society with permitted polygamy, there's a high chance that a large portion of less-successful (straight) males would end up with no female partnership. This is a recipe for social disorder if there ever was one - it's well known from sociological and psychological research that males in long term relationships are far less likely to engage in risky, asocial, or criminal behavior; and are more likely to be more socially productive. Or, like, not engage in mass violence and rioting.

In practice, there is tons of research that polygamy has bad outcomes, although in all honesty, I haven't vetted ANY of the following links and don't know how solid (or biased) the research is. YMMV, PATYR.

  • The Perils of Polygamy has some in depth discussion (note: it seems to be a socially conservative think tank, so they clearly have an axe to grind).

  • The pros and cons of polygamy from Psychology Today. They often have progressive bent in my limited experience (as in, publish articles how conservatism is a mental disorder, in full seriousness) so probably also have a different axe to grind.

  • Slate lists a study highlighting problems. Again, progressive axe grinding is likely.

  • The Atlantic had an article critical of polygamy from societal standpoint, largely drawing from non-poly-related study of male-surplus Asian societies in 2004 book "Bare Branches: Security Implications of Asia's Surplus Male Population" by Valerie M. Hudson and Andrea M. den Boer.

Having said that, the above reasoning and arguments are NOT the purpose of anti-poly laws, although they may be used by defenders of such laws. The purpose stated above is the only one - to placate the majority of population that for one reason or another supports such laws.

[1] and if that 63% people who find homosexual relations morally acceptable seems low - that's only 6% less than 69% who find sex outside marriage morally acceptable. As in, only 6% more people don't accept homosexuality than "living in sin"

[2] Then again, one has to wonder at how much social acceptability bias affected that poll, since a staggeringly low 9% considers extramarital affairs "morally acceptable", compared to between 20 and 70% estimates of people actually cheating.

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    Good answer, thanks. However, one thing is missing. Do you have statistics on the amount of the population that object to polygamy?
    – Charlie
    Sep 23, 2017 at 22:17
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    Given that polyamory exists even without legal marriage options, it seems the dangers of it aren't very high. Most polyamorous people seem quite happy with it.
    – Erik
    Sep 23, 2017 at 22:19
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    @Charlie - added polling.
    – user4012
    Sep 23, 2017 at 23:24
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    Is it worth mentioning the inherent additional complexity of next-of-kin relationships? If someone was in a coma and had two spouses, what if they disagreed about medical decisions? Then again, that may not actually be so different from a child where the parents disagree...
    – Bobson
    Sep 25, 2017 at 11:15
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    @LangLangC MRA is men's rights activism, but that covers a lot of topics. The hypergamy thing is more associated with the so-called "manosphere", which has overlap with MRA but is a distinct thing. Dec 10, 2018 at 23:37

Currently, anti-polygamy laws serve to "protect" traditional marriage (at least, traditional in the eyes of the Christian West) the same way that laws against same-sex marriage were supposed to. Note that these laws apply only to the legal institution of marriage, not the religious institution.

Unlike prohibitions against same-sex marriage, I doubt that prohibitions against polygamous marriage will be overturned anytime soon for the following reasons:

  1. Same-sex marriages don't introduce the legal headaches for custody, power of attorney, property rights, inheritance, etc., that polygamous marriages would. How would you apportion assets in a poly divorce when a partner leaves? When multiple partners leave? How about parental rights?

  2. Right now, polygamy (at least in the US) is most closely associated with some groups that are, let's face it, pretty far out on the fringe socially and politically, and it's not the polygamy that makes them so fringey.

  3. There are arguments that poly marriages (especially polygyny, multiple wives for a single husband) truly are bad arrangements in a number of objectively measurable ways, although I don't know how solid those arguments are. But they're not the silly slippery slope arguments employed against allowing same-sex marriage ("why, next thing you know, people will be marrying their pets").

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    3) is only true because of the strong impression of looking at the fringe groups in 2) for how it works. There are many happily-together poly couples, you just don't see/hear much about them because being poly gets a bad rep.
    – Erik
    Dec 11, 2018 at 13:34

To ration females to males in equal share for everyone. Prohibition of polygamy, if combined with no sex outside marriage, will ensure the poorest ugliest dumbest males will still be able to get a wife.

Why "society" bother doing that? Well, the poorest, ugliest, dumbest males can vote. Politicians want their vote.

If polygamy are allowed, guys like Donald Trump/Bradd Pitt can get 5-10k wives, and many guys will get none. That's because men, if allowed, will aim for quantity. Look at Sultans and emperors. To prevent that, the laws "ration" females in equal share for everyone.

Yes. Women are still legal to choose poor men. However, if those women can choose to share richer smarter men instead, will they? It's like employers can still legally hire Americans. But if those employers can hire cheaper immigrants instead, will they?

Men will instinctively sabotage their competitors. So marriage laws in democratic countries allow women to pick only singles.

Matt Ridley in his book Red Queen says something along, "Far from laws protecting women ... anti polygamy statues really protect men"

Here is the quote and the whole argument


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In democratic countries, the majority rules.

The majority of people are not alpha males.

So they choose to ban polygamy.

In general, we get free competition, if a small number of people compete for the benefit of majority.

For examples, most businesses compete with each other. The majority of people are benefited from their competition and hence force businesses to compete.

However, competing is not a good idea for profit.

If the majority is the competitor, we usually have trade restrictions.

The trade restrictions are in favor of majority.

For example, we got many trade restrictions in labor market. That's because laborers are majority compared to employers. Laborers are significant "voting bloc" so to speak.

Majority of men are poor or middle classes. So marriage laws in many democratic countries tend to kick out the rich from mating market.

For example, within marriage, alimony tend to be proportional to wealth of a man. This discourage richer men from getting married. Using money to get girls tend to be heavily discouraged. Explicit use of using money to get girls, called prostitution, is prohibited.

Like all marriage, the states heavily influence who can marry who.

In states that allow polygamy, who would stop the law makers from saying that girls can only marry guys that vote for me or embrace my religions? That means the religious leaders, or the alpha males, pretty much become pimp of all girls. Only by obeying the whim of those alpha males, usually called religion, a man can get laid.

No wonder, middle east often have war.

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    @Orangesandlemons - "almost entirely a Christian phenomenon" - you must not have been on any feminist blogs or other sources recently.
    – user4012
    Dec 11, 2018 at 12:58
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    It's hard to imagine that any western 21st century legislative body would introduce polygamy without also introducing polyandry. In that case the whole argument "not enough wifes for all men" breaks down, because multiple men can also share a wife.
    – Philipp
    Dec 11, 2018 at 15:52
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    @Philipp Assuming men are equally likely to accept their wife having multiple husbands as women are to accept their husband having multiple wives. Dec 13, 2018 at 5:53
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    @Philipp: Just to keep our terminology straigth: As I explained in my comment to the Q, "polygamy" is the gender-independent term (at least according to the dictionaries I checked). The gender-specific terms are "polyandry" (multiple husbands, as you correctly wrote) and "polygyny" (multiple wifes). I hate it if people mix up definitions, and it confuses everyone :-).
    – sleske
    Dec 14, 2018 at 7:18
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    If polygamy are allowed, guys like Donald Trump will have 5-10k wives, and you will get none. That's because men, if allowed, will aim for quantity. Look at Sultans and emperors. To prevent that, the laws "ration" females in equal share for everyone.
    – user4951
    Dec 16, 2018 at 19:18

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