The cuckoldry rate in complex agricultural societies is probably ~1%

One of the most interesting and strange things I’ve ever posted about has to do with extra-pair paternity rates. Basically, the rate of cuckoldry.

I first got interested in the topic because people kept bringing up the chestnut that 10% of children have misattributed biological paternity. That is, their biological father is different than the father who raises them. This is a “fact” I’ve encountered from many biologists and the public. But like the “fact” that you use only 10% of your brain, this seems more an infectious meme than a true fact.

The problem with ascertaining paternity is to get a representative sample. And, to get deep time depth you need good genealogical records. With genetic analysis new methods also came to the fore: analyzing the distribution of Y chromosomes within a lineage.

As far back as the middle 2000s Anderson had published How Well Does Paternity Confidence Match Actual Paternity?, which surveyed the literature and found that the rate of misattributed paternity was closer to a few percent than 10%. Later work found results closer to ~1% in places like Western Europe.

A new paper out of the Netherlands confirms this figure. This turns out to be the same proportion as in Flanders, just to the south. The authors wanted to compare the results with Flanders because it is an adjacent area with the same ethnicity (Dutch), but which went through industrialization much more quickly. Therefore it was a test of hypotheses about urbanization and extra-pair paternity.

How generalizable are these results? It seems entirely likely that the 1% figure applies across the Eurasian oikoumene (genotyping and surname analysis in China has found a similar number). And yet if extra-pair paternity is so low why are there so many cultural strictures on mate guarding in these societies?

Much of the above paper discusses the evolutionary psychological mechanisms which evolved to combat cuckoldry and the arms race with occurred as females sought “higher quality” sperm donors. In short, if paternity uncertainty is so minimal then presumably this is not a major recent evolutionary pressure.

The curious thing about these results, which are replicated in numerous studies, is the denial they elicit. There is an online “cuckold community” which does not appreciate that their fetish is not as common as the old 10% number implies (I know about this community due to referrals from message boards). Then there are “men’s rights” activists, who simply can’t believe that women exhibit such fidelity. Finally, there are the sorts who wish to tear down bourgeois sexual norms, and valorize a past which did not exist.

But the ultimate question has to do with human nature and modal behaviors in the past and across different societies. These results establish that low misattributed paternity societies can exist at equilibrium and that they are rather common. They do not establish this was the “environment of evolutionary adaptedness.” We simply don’t know enough about this topic, but, I do think there needs to be an appropriate synthesis between the evolutionary psychological outlook exemplified by The Blank Slate and the cognitively informed behavioral ecology found in The Secret of Our Success.

My own suspicion is that human cultures and behavioral scripts exhibit discrete modalities, but we’re mildly flexible. An economistic “modes of production” analysis would probably smoke out differences. More precisely I think the more economic independence that women in a society have the more likely paternity certainty is going to be a major issue because many men will reduce their investment to any given offspring. Although such economic independence is often conceived of as a modern development in gender relations, there are actually societies where women have been the dominant primary producers, because of a less intensive, more extensive, sort of agriculture (ergo, less premium on physical strength).

15 thoughts on “The cuckoldry rate in complex agricultural societies is probably ~1%

  1. It continues to annoy me that I “learned” that 10% factoid in one of my college biology classes, direct from the professor. Early 90s, though I don’t think that excuses it.

  2. dude, it was “taught” to me at a graduate level behavioral ecology seminar in 2012! i had to get into a mild dispute with the professor about. didn’t want to be a dick…but k. anderson’s paper was published in 2006 (and had been circulating as a preprint a while before that).

  3. I heard this “fact” and was always very skeptical about it, especially in what was still quite traditional East Asia where (and when) I grew up.

    Back then, the cost for women when they were discovered having extra-marital affairs, let alone having children as the results of the said affairs, was CATASTROPHIC. It would expose ALL the children to serious doubts about paternity. The husbands could then divorce the women, keep all or most of the joint property, and then could choose to either take the children from the former wives (if certain of paternity) or abandon them to the now property-less and penny-less wives (if suspected of alternate paternity). And on top of that cherry was that women were sometimes criminally prosecuted for adultery (men rarely were).

    So, from what I could tell, this kind of social and interpersonal transgression by females was something that happened very rarely, and when it did happen, was something that was harshly punished by society, in part to serve as a warning to others. In this atmosphere, the alleged cuckoldry rate of 10% or above seemed ridiculous.

    And I didn’t think it was all that different in Europe until relatively recently (post-WWII, perhaps?).

  4. And I didn’t think it was all that different in Europe until relatively recently (post-WWII, perhaps?).

    i assume so.

    one thing though: the social science suggests in developed societies that paternity certainty is almost never an issue for middle to upper class males. the issue crops up as you go down the socioeconomic ladder. if in the past most people descend from the higher orders the % might seem lower in part because higher class males left descendants. OTOH, the ethnography indicates that higher class males are the ones who are contributing genes to the lower classes….

  5. “How generalizable are these results? It seems entirely likely that the 1% figure applies across the Eurasian oikoumene (genotyping and surname analysis in China has found a similar number). And yet if extra-pair paternity is so low why are there so many cultural strictures on mate guarding in these societies?”

    Because the cultural strictures on mate guarding are what causes the low extra-pair paternity rate?

    “Then there are “men’s rights” activists, who simply can’t believe that women exhibit such fidelity.”

    It’s not really as dramatic as it seems: it’s not that only 1% of women cheated on their husbands, if a woman cheated but no kids were born, it isn’t counted, while if a woman cheated but the husband’s sperm won the race half the time, it’s only half-counted. It’s also sheds much less light on modern people than it does on those who lived in the pre birth control era, moderns can use birth control to hide infidelity. Surveys have shown that self-reported women’s adultery is somewhere between 5-20%. The 10% number should have been unbelievable even before the genetics came out: it would imply a huge amount of infidelity.

  6. “Much of the above paper discusses the evolutionary psychological mechanisms which evolved to combat cuckoldry and the arms race with occurred as females sought “higher quality” sperm donors. In short, if paternity uncertainty is so minimal then presumably this is not a major recent evolutionary pressure.”

    But cuckoldry is not the only reason for mate-guarding. If a man doesn’t guard his mate who is seduced by another man, but leaves her husband before starting the relationship with him, he isn’t cucked, but he is screwed. Also, I don’t think the main reason women throw themselves after powerful men is so they can get superior “sperm donors.” It isn’t that the King’s genes are superior, he’s just some fat guy who was born in that position, but because he can direct resources toward her and her children.

  7. A really low cuckoldry rate (around 1%) would fit with the best figure I’ve found for infidelity estimates over the years (it was around a 25% lifetime chance that someone would commit infidelity). Of course, measuring such things tends to be quite difficult.

    In any case, the future of routine genetic and other testing of newborn children might almost eradicate cuckoldry altogether (aside from the community you described). If you’re not the biological father of a new child, then you’ll know very quickly.

  8. Mate guarding was done in most higher developed cultures by the whole family or even clan, it wasn’t just the husband looking after his wife. And a huge advantage of guarded and largely controlled females in patriarchal societies is, that it drastically reduces the infights between related males of the same clan or even tribe. If the rules are clear and females are under the male’s family control, things should be easier for male cooperation.

  9. File this under anecdotal corroboration, but one of the things that stood out to me as I did some research on my paternal haplogroup is how amazingly consistent it has been.

    That is, my rare and unusual Y-DNA haplogroup can be traced to cousins some 10 generations removed with my same surname. Not only does that mean an unbroken line of patrilineage from me to my ancestor of the same surname, but also to my various different distant cousins. It is remarkable how persistent it has been.

  10. @ohwilleke:Why so? Most women cheated in their own group, with intensive contacts to outgroup males being the exception.
    Actually it is much more dangerous for the female to copulate with foreign looking males for obvious reasons. Whereas its much more difficult for many reasons to catch a treacherous man of the own family. Thats why ydna alone is no sure thing by the way, if brothers or cousins were involved.

  11. “How do surname\Y chromosome comparisons account for adoptions? Is it just too new a custom to matter?”

    Widows with children remarrying and children taking the new husband’s name is another form of adoption that seems likely to have happened a fair amount, even a long time ago.

  12. The alleged premium on male strength in production has been wildly overrated. (Warfare is a different matter). The key question has always been (until very recently) “can you do it while minding the kids”. If you can, women do it (e.g. foraging and hoe farming). If you can’t, men do it (e.g. hunting, pastoralism and plough farming).

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