Why do marriages fail?

Since I’m Indian, people occasionally ask me about arranged marriages (Indian-style) versus “love” marriages (western style). Invariably, and to my surprise, these people express their admiration at how well arranged marriages seem to work out.

Of course, no one really knows how well arranged marriages work. Sure, the divorce rate in India is much lower than it is here, but that’s partially (and I’d say mostly) because social pressures there strongly disfavor divorce. To get a more accurate test of marriage strategy success, you’d have to poll the happiness of people who remained married as well.

There’s still the question of why arranged marriage works as well as it does. (Especially since, despite the common misconception, families don’t really seem select partners with any measure of personality compatibility in mind.) … and also why love marriage doesn’t do so hot, despite its seemingly perfect ideal.

Naturally, having experienced no form of marriage at all, I have some theories.

Arranged marriages, when they work, succeed because of well-placed expectations.
You’re more comfortable with the fact that you’re getting married than you are with the person to whom you’re getting married. But maybe that understanding helps you survive the institution regardless of who that other person is.

Hrmm, I guess that’s all I can figure out about arranged marriages. But what about marriages in the US? How does that famous 50% divorce rate come about? Of course, there are the common reasons (infidelity, etc.) but here are some less obvious ones that might still be significant.

There is a tendency to believe that being in love is the prerequisite for marriage.
You’re in love. You get married. Makes sense… in the idealistic abstraction of American values that you absorb from TV and the movies during your formative years. Obviously a successful marriage requires some significant personality- and belief-based similarities as well. (And perhaps they’re more important, in the long run?) But when you’re love it’s harder to see that, so out come the wedding bells — and the subsequent disillusionment and failure.

Some people are not built for marriage.
Well, that sounds controversial. But consider the following points: (1) Humans evolved for polygyny, not monogamy. (As I’ve mentioned in an earlier post, monogamy puts most females at a disadvantage.) So it’s not a given that the requirements for a successful marriage are inherent or expressible in all humans. (2) It seems (to me) that for a marriage to last half a century or longer, the couple involved needs to be under significant social pressure — or share a large measure of patience, forgiveness, and who knows what other qualities. It seems conceivable that some people just do not possess these traits. (And it takes only one person to ruin a marriage.) And yet, as in the previous point, it’s easy to overlook missing traits and get married. And then reality sets in.

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11 Responses to Why do marriages fail?

  1. Anonymous says:

    Hmm…

    1) While I don’t think there’s strong evidence that humans evolved “for” monogamy, I think it’s a huge mistake to say they evolved “for” polygyny. Also, most existing polygynous marriage systems have been shown to be harmful to women (for instance, non-sororal polygyny of the Dogon of Mali). Infant and child mortality is higher for women with more co-wives.* Both polygyny and monogamy are patriarchal systems.**

    *Bev Strassmann has a chapter in the book “Adaptation and Human Behavior” on this (2001). I believe she also has an article in 2000.
    **Sarah Blaffer Hrdy and Barbara Smuts have written great articles on the evolution of patriarchy. While as primatologists they do spend some time on “polygyny” as being useful to females in terms of maximizing choice, we just don’t have any evidence that any hominins were or could have been polygynous in the same way. And even if we did, that doesn’t mean humans “evolved for polygyny,” it just means it’s in our heritage. Whatever the case, polygyny as it exists now is possibly more harmful to women than monogamy.

    • aj says:

      Re: Hmm…

      I’m not sure I agree with some of the points you’re making, but I think on others we might agree with just a bit of clarification. (I’m not sure exactly what patriarchy has to do with these claims, so I apologize for not responding to that bit.)

      “Humans evolved for polygyny”: I agree that this is sloppy language, in the sense that evolution is directionless with respect to particular features (though very “directionful” with respect to reproductive success). However, directioned language is often used as a shorthand in describing adaptations, as in “bats evolved echo-location for navigation” or “the gene acts selfishly”. So, to clarify, what I mean is: “Several human adaptations are characteristic of polygynous species. Furthermore, there is a large body of evidence to suggest that humans were in fact polygynous.”

      Signs that point to evolved polygyny:

      Sexual dimorphism suggests polygyny, and humans are dimorphic.
      “If a costly investment in body growth and maintenance has been sexually selected, then we can predict that there must be exception reproductive rewards to be gained by large males. If this is true, then males should be very large (and greatly outweigh females) in those species in which males can monopolize many females, while sexual dimorphism in body size should be least in those species whose males are limited to one or two mates per breeding season. This prediction is supported by body length data from several mammalian groups.” [Animal Behavior, Alcock]

      In humans, males and females are not the same size. Males are, on average, taller and heavier.
      “Humans show sexual dimorphism in several traits. Compared to females, males on average have more height and mass, more upper-body strength, higher metabolic rates, more facial and bodily hair, deeper voices, larger brains, and riskier life histories, with higher juvenile mortality, later sexual maturity, and earlier death (Ankney, 1992; Daly & Wilson, 1983, 1988; Ghesquiere, Martin, & Newcombe, 1985; Rushton, 1995; Short & Balaban, 1994). Our moderate size dimorphism is consistent with our species having evolved under a moderately polygynous mating system, with more intense sexual competition between males than between females (Fleagle, Kay, & Simons, 1980; Martin, Willner, & Dettling, 1994).” [Handbook of Evolutionary Psychology, Crawford & Krebs]

      In most societies, polygyny is allowed.
      “A substantial majority of human societies legally permit a man more than one wife.” [Sex, Evolution, and Behavior, Daly & Wilson]

      “Throughout human evolution, polygyny has almost certainly been practiced by men able to afford multiple partners, judging from the widespread occurrence of culturally sanctioned polygyny in historical times.” [Ethnographic Atlas, Murdock]

      Exact percentages from Murdock: 16% monogamy, 0.5% polyandry, 83% polygyny.

      In pre-birth-control societies, polygyny is beneficial to females.
      “Several studies of traditional societies in Africa and Iran have shown a positive correlation between a woman’s fitness and her husband’s wealth, measured in terms of land owned or number of domestic animals in the husband’s herds, even though polygyny is permitted in all these groups. Women married to rich polygynists need not pay a fitness penalty, since one-half or one-third of a great deal can be more than all of a poor man’s holdings–the same argument developed to explain female acceptance of polygynist mates in birds and other animals.” [Animal Behavior, Alcock]

      In this context, fitness is the number of the woman’s genes that survive to the next generation.

      “Whatever the case, polygyny as it exists now is possibly more harmful to women than monogamy.” I can believe this. Regardless of this fact, however, polygyny as it existed in humans was a viable and frequently practiced reproductive strategy. The point in my post was that monogamy is relatively recent, and thus it is unlikely that humans have many adaptations to support it. Of course, our brains are locally adaptable — but again, all I was saying is that it is not given that humans are suited for long-term monogamous marriage.

      • Anonymous says:

        Re: Hmm…

        I made the comment on patriarchy because the evolution of patriarchy has everything to do with how well females in a given population fare. Patricia Gowaty has a great edited volume on sexual dialectics that is useful.

        For your first point, your Alcock quote states “If this is true, then males should be very large (and greatly outweigh females) in those species in which males can monopolize many females.” In societies with a surplus of energy, like the US, males are on average 15% bigger than females. In societies hurting for energy — which is more likely how we evolved — males aren’t that much bigger than females. Ache Amerindian males are about one inch taller than females. You see similar trends in other foraging populations.

        Now, males are certainly stronger even in those populations where they’re not bigger, but this doesn’t point to the kinds of “very large,” overwhelming size needed in other animal populations to have polygyny.

        Your second point, that polygyny is allowed in most populations, is definitely true. However I think more recent looks at this data have qualified this statement. I think more important and relevant is the idea of serial monogamy — in most populations that practice polygyny, serial monogamy is far more prevalent.

        There’s also a lot of evidence that humans evolved under an egalitarian society, and enough sharing of wealth in forager societies that no males necessarily have enough wealth to attract or buy multiple wives. (That said, the Ache Amerindians have some polygyny, and it is unrelated to size or wealth, but may be related to hunting prowess or status in the group.) That’s not to say I have a rosy view of hominin evolution, just that I think the story is more complex than “marriage and monogamy aren’t what we humans evolved for.”

        On your last point, the Dogon of Mali example I mentioned above *is* a natural fertility (non-birth control) population, and Strassmann’s work is considered directly contradictory to the bird Polygyny Threshold Model that Alcock alludes to.

        Anyway, I agree that it’s not given that humans are suited for long-term monogamous marriage. But I don’t think they’re suited for polygyny, nor do I think any early reproductive strategy necessarily reflects current human behavior. But then, I am adamantly not an adaptationist :).

        • aj says:

          Re: Hmm…

          Interesting points.

          “In societies with a surplus of energy, like the US, males are on average 15% bigger than females. In societies hurting for energy — which is more likely how we evolved — males aren’t that much bigger than females. Ache Amerindian males are about one inch taller than females. You see similar trends in other foraging populations.”
          But this doesn’t matter, of course. Dimorphism doesn’t require that “all males are larger”, just that “successful males are larger”, which would be the case with a male with an adequate supply of nutrition. The fact that the average male is underfed or undersized is expected in a polygynous society, in which only a few successful males attract many mates.

          I definitely agree about serial monogamy — but it’s not strict monogamy in the sense I was talking about in my post. Getting divorced is exactly the action I was analyzing!

          “There’s also a lot of evidence that humans evolved under an egalitarian society, and enough sharing of wealth in forager societies that no males necessarily have enough wealth to attract or buy multiple wives.”
          I’d be curious to hear more about this.

          “Nor do I think any early reproductive strategy necessarily reflects current human behavior.” Of course by early we mean “for the first 99% of human history”. I do agree that our actions now are most certainly not just a function of our EEA. But my point was not that “humans were polygynous so we should expect to see adaptation X”; it was, rather, “humans were not strictly monogamous so we have no reason to expect adaptation X”, which I think is a much weaker statement.

          I think in this, we both agree: it’s a complicated story. In my mind, it’s complicated enough that I don’t see any reason for some evolutionary support of (non-serial) monogamy, unlike for other social interactions, like language and altruism.

        • aj says:

          Re: Hmm…

          And by the way, I think this conversation has really helped clarify some of the vaguer, poorly-substantiated claims in my original post. Thanks. I was really tempted to revise the post to reflect these clarifications, but then these comments wouldn’t make any sense! So instead I’ll hope people bother reading the comments.

          • Anonymous says:

            Re: Hmm…

            Glad I could help clarify things :).

            And yes, I know the serial monogamy thing backs up your point about divorce… I guess the point I was trying to make is that evidence in our history for serial monogamy is a better explanation for the divorce rate than evidence in our history for polygyny.

          • Anonymous says:

            Re: Hmm…

            Oops, didn’t see where you said you’d be curious to hear more about the egalitarian stuff. I’d mostly just point you to Kim Hill and Magdalena Hurtado’s book “Ache Life History” (or their articles) and anything you can find about the Hadza (Marlowe, Hawkes, and Kaplan are names I can think of associated with that fieldsite). I know the Ache practice some polygyny but I don’t think the Hadza do. In any case, there isn’t a ton of variation within the populations in male reproductive function or health. In the Ache, the male’s ability to get multiple wives is unrelated to whether they’re any bigger than the other males — they’re all five foot one and have low testosterone concentrations! Rather, it appears to be related to hunting prowess (which takes about twenty years to get good at). More recently in the Ache, because they live on reservations and have more contact with Paraguayans, my understanding is that males are marrying a bit younger, and the females are choosing males that learn to speak Spanish and negotiate well with Paraguayans and missionaries (I don’t think that’s empirically shown, that’s just what I’ve heard from folks who work there).

            Hope that points you in the right direction to learn more if you’re interested…

    • aj says:

      Yeah I actually really like Gottman’s work (and always thought it would be fun to be analyzed by his group when I’m dating someone). I wonder what his workshops consist of and how he deems them successful.

      Of course, I’d be even happier if he tackled some of the hypothetical issues I’ve raised here. :)

  2. Anonymous says:

    Subject1

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