Polygamy Sucks for Women (In Terms of Genetic Sexual Selection)

Any idiot in the world knows that polygamy is a much better deal for the men in the society than the women. A free pass to run around with as many women as you can possibly attract? Most guys would sign up for two of those, thank you very much.

But aside from the obvious moral dilemmas and hatchets sunk into the back of the skull from having sex with multiple women, the practice opens up some interesting questions related to evolution and sexual pressures on passing on genetic traits. According to a new study from Indiana University evolutionary biologist Michael Wade, the act practice of polygamy is a boon for men in this department but a bust for the women. Even in evolutionary terms, women with sister-wives get the short end of the stick.

The study comes from a rigorously kept data set from Mormon communities in Utah on people born between the years of 1830 and 1894. For whatever reason, there are extremely detailed and accurate records relating to deaths, births and parental lines during this time. But the most interesting part is the opportunity to study what happens to a single population when it switches from polygamy to monogamy.

There are plenty of species in the world that practice both, but you’d be hard pressed to find another species besides humans that have switched from one to the other. I’m no expert, but I’m guessing there aren’t any. And though humans practice both, comparisons can be tricky because of the geographic and cultural differences of societies that practice one or the other. The act of suddenly and relatively switching from one to the other is rather unique.

Polygamy hit its peak in the Utah Mormon community in 1833 when 17.8% in men born in 1833, of which 17.8% of all married men took advantage of having free reign to keep sleeping around. But this percentage dropped like a rock within a handful of years, dropping below 1% by the time of the Morrill Anti-Bigamy Act of 1862, which outlawed the practice in the United States. Near the turn of the century, after two failed appeals, the Church of Latter-Day Saints followed suit and banned the practice themselves.

But what did this switch do the evolutionary fitness of men and women? How did their ability to pass on their genetics to the next generation react? What are the inherent differences in the two systems?

According to the data, quite a bit.

Thanks to the meticulous records mentioned earlier, the scientists were able to look at data from nearly 180,000 adults and their 630,000 children who lived or died between 1830 and 1894. And the results were pretty clearly in favor of the Brad Pitts of the world. That is, socially and sexually dominant males lucky enough to partake.

The number of mates for males was 300% higher than women in the early 1830’s but just 25.9% higher by the end of the century. Put that together with an average of an extra four or five children sired by each man’s sister-wife, and you end up with a clear reproductive sexual selection advantage for these men.

In contrast, being a sister-wife actually hurt the women involved. Statistically, they bore one less child than women not included in a harem. Just as theory predicted, the advent of monogamy reduced the strength of sexual selection on males by 58 percent.

In short, the general practice of monogamy is quite a good thing – evolutionarily speaking – for those of us not lucky enough to be born with dashing good looks, Herculean strength or Daddy Warbucks’ pockets, as well as women in general. Otherwise, we’d all be much less likely to keep our genes in the pool.

*Post corrected on January 20, 2012 thanks to an observant reader

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About bigkingken

A science writer dedicated to proving that the Big Ten - or the Committee on Institutional Cooperation, if you will - is more than athletics.
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13 Responses to Polygamy Sucks for Women (In Terms of Genetic Sexual Selection)

  1. Helene says:

    There is so much sarcasm and hyperbole in this article, that it is a little hard to follow. In addition to the obvious fact that there no more than about 7 family names in Short Creek, one look at the faces of the FLDS shows everybody looks like everybody else. And they don’t look (or act) very bright. Nuff said.

    • bigkingken says:

      Sorry, let me try to be clearer without trying to be cute. Basically one theory on sexual selection and evolution is that individuals do whatever they can to ensure their genetics get passed down. This includes both having more offspring and trying to ensure that the offspring survive to have their own. The study showed that in this regard, polygamy is better than monogamy for men who are able to take many wives because they have more offspring, though it might be worse for men who can’t attract a mate. However, it also shows that polygamy is worse for women because – on average – they have one less child than when they are in monogamous societies. Hope that helps.

  2. Helene says:

    Yes, that made your point clear, and it is an interesting point, which I hadn’t thought of in just that way.

    I am surprised though at the data. From my readings, many of the families in the fundamentalist Mormon communities (of which, granted, the FLDS is only one) are huge, with each co-wife having 7,8,10, sometimes 14 children. This leads to a steady increase in the size of the quite closed community, but with a less varied gene pool.

    I don’t think anyone, (except true believers, both female and male) would dispute that polygamy is a better experience for men than for women. However, if one looks at the steady diminution of genetic variety in conservative and closed polygamous societies, one sees a continous reduction of contribution from the male line, compared to the female line. (Although that side is limited also by the injunction against marrying outside the group.)

    Although individuals specifically inherit problems in a very painful present, I think of the impact of lack of genetic variety as being reaped primarily by the group, and as unfolding in the future.

    Great article. Thanks.

  3. missahliss says:

    You shouldn’t hate on polygamy if you don’t understand it.

    • bigkingken says:

      If you read the post, I never make any disparaging remarks about the practice, its morality or its place in society. I do say that most women would have a problem being with a polygamous husband, which I think is true for most of the world. The rest is a scientific study about the pros and cons of polygamy versus monogamy for a individuals in a species, all biologically speaking. I certainly wouldn’t call that hating on polygamy or making any type of judgements about the practice at all.

      • J says:

        You wrote the phrase “aside from the obvious moral dilemmas”. This is a disparaging remark on polygamy in the context of morality, and it is certainly a judgement. “Most people” is not an argument anywhere in the world that I am aware.

        Your other arguments also tend toward speciousness. There are always sexual selection advantages and disadvantages. The field is never even, and a lot of that reason is often rooted in very relative social norms that vary from culture to culture. Making a negative judgement of the fact that it is the males who enjoy a selection bias in this culture is a simple bias of your own. Your statements regarding less children per woman is not borne out in my observation, Even if it were, you are commodifying genes at the expense of culture and family. It makes no practical sense.

        Inbreeding to the degree that children are at risk of birth defects is not competitive, to put in in your Darwinian terms. Incest is wrong. However, your generalized inferences about the nature of the gene pool are also inaccurate. There are widely acknowledged correlations between too much genetic disparity and birth defects, as well as lesser genetic distance and higher intelligence in offspring. The Ashkenazim are a widely studied group that bears out the latter point of fact.

  4. Jim Fitch says:

    Here’s a question for the author…You state, “Polygamy hit its peak in the Utah Mormon community in 1833 when 17.8% of all married men took advantage of having free reign to keep sleeping around.”
    Exactly which Utah Mormon community existed that year?
    My understanding is that Mormons did not trek to Utah until more than a decade later!
    If you are going to make a statement, please do your best to not prove yourself to be incompetent to make intelligent conversation.

    • bigkingken says:

      You’re absolutely correct. Thanks for the catch. I misread the original publication that this post is based on. I somehow missed the very important phrase “born in.” As such, the post should read, “Polygamy hit its peak in the Utah Mormon community in men born in 1833, of which 17.8% of all married men took advantage of having free reign to keep sleeping around.” I have updated the post. Thanks for your catch.

  5. Gloria Minetta von Fürstenberg says:

    What a bunch of pseudoscientific politicized rubbish. You present human beings in a repulsive light that doesn’t bear at all upon the reality of the situation. Most women in polygamous marriages are not pleased by the situation, preferring to have a one on one relationship with men. It has nothing to do with gene passing nonsense unless you are ready to assert that we are coded arbitrarily to behave and “prefer” things which end up causing “our” genes (there really is no such thing as belonging a gene, btw; you got it from your parents) to be included in offspring. But in that case, all our behavior is merely an unintelligible farce that has the effect of propagating certain genes, not because of some inherent purpose but rather because it just happens to have the effect of producing something that perpetuates itself. You’re trying to have your cake and eat it. Either love is just an arbitrary whatever-it-is part of arbitrary things (humans) that arbitrarily produce other things which behave similarly (meaning, we don’t exist to survive; we survive and and replicate therefore the chain pointless continues), or people enter into relationships because they have real meaning and not just a set of mechanical steps we’re programmed to perform. To pull off the first requires a serious cherrypicking, ignoring one’s one experience, and a serious ignorance of the nature of science.

    And besides, what man wants more than one wife? You have to be some nerd who’s lived his entire life in a cave and developed some delusional idea of woman other than just other humans. One wife is one burden enough. And honestly, men with character don’t go around sleeping with as much as he can. Women less so. If you were human and actually had a social life, you’d know that women are far more attached to men and skittish. I smell resentment wafting my way. Take a shower instead of indulging in pop science drivel.

    And btw, Brad Pitt is a stupid example. You are clearly writing form a (shallow, stupid) male perspective. He’s a dumb fop. and you’re a vapid geek who needs to live life as it is instead of believing warped models that have no bearing on reality (except perhaps incidentally with respect to the data, and not the interpretation). You’re like a creationist, only dumber. Game theory does not apply to reality. Having sex is not exactly a big deal (uh, you along with over 6 billion other stinking ape-like creatures exist because of it) — if anything, NOT keeping your pickle jarred or your legs shut is a miracle these days. We are also attracted to different people. We’re not all just looking for use another to “spread our genes”. That’s absolutely mind-numbingly moronic.

    But then again, if you keep thinking the way you do, then perhaps there’s hope in that YOU won’t spread your filth and produce disgusting spawn, infecting the population with something that should never see the light of day, or the darkness of night for that matter. Feel deep shame for existing.

    • bigkingken says:

      I don’t believe I ever claimed that there is no such thing as love or that our behaviors are controlled by nothing but genetics and Darwinian processes. I just reported the results of a research paper that I thought was interesting. And all that it said was that polygamy is disadvantageous for human females in a Darwinian light. However, I’m sure the women in that community – and humans in general for that matter – gave less than a shit about that.

      The only reason the study looks at humans rather than another species is because there isn’t another animal whose community could suddenly switch from polygamy to monogamy, which is the only way to reduce as many variables as possible. You won’t find dolphins or lions suddenly becoming monogamous simply because they choose too expressly because those animals do operate solely on instincts in order to pass on their genetic material, while humans obviously do not. Even that being said, you’d probably have a tough time trying to extend these results to any other species simply because they lack emotions. I’m sure everything you mentioned played a role in the way that community behaved before and after the switch to monogamy.

      As for the way that people are presented, are you upset that they’re just statistics in a study having to do with relationships? Do you also get this upset when studies look to see if good looking spokespeople sell more products in advertisements, what characteristics people seem to prefer in a partner or if speed dating is a good way to date? There are countless studies dealing with love and relationships that take on a statistical approach simply because that’s the way that science is done. Sure, an individual person makes decisions based on life experiences and emotions that may or may not be the same as others, but that doesn’t mean that you can’t look at the way people behave on average.

      I might also mention that there are plenty of Mormons – and other communities – out there today who rather enjoy polygamy – both men and women. I don’t claim to understand it, but they’re out there.

    • Maria says:

      What a close minded, sub-educational, misrepresentation of this article. Clearly the person who wrote this response was having a bad day. What was the purpose for the attack on the writer as a person? I apprectiate the facts presented, they gave me a couple stable points to utilize in discussion. Brad Pitt is a popular icon, using him as an example was to get a point across, your attraction to him is irrelevant. This article is discussing statistical facts, not theorized intentions. If you don’t believe that there are men and women in this world practicing and enjoying a polygamous lifestyle, then you are the one mal-informed.

    • Jessica says:

      I couldn’t even read all of that nonsense xD What a hater. And by the way, “dumber” is not a word. 🙂 I believe that you should be the one that should “Feel deep shame for existing.” Haters like yourself are what make the internet such a horrible place to debate and share opinions. If you do decide to reply to this, which I doubt, please at least attempt to sound somewhat intelligent and not like a 6 year old on their mommy’s computer 🙂

  6. It’s a very interesting study, but the metric of “sheer number of offspring” is too limited. Women in general, in evolutionary terms, seek high-value male partners that can provide significant social and material resources and support.

    So, on that count, since generally the only men through history who could manage polygynous marriages were very high-status and high-ranking in society, many women probably preferred these arrangements over strict monogyny. If a woman could choose an exclusive relationship with a poor man, or a polygynous arrangement with a rich man who had 2 or 3 other wives, she would probably choose the latter. Although she may on average have fewer total children, her children will be of greater “quality” in the sense of health, strength, social standing, intelligence, material resources, confidence and other qualities that are presumably implied by a man with high social power and value.

    Bottom line: polygyny does not necessarily “suck” for women in terms of genetic sexual selection. There are other measures of genetic success than sheer number of offspring.

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