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What If 1 Out of 10 Men Were Cuckolded?
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220px-Great_Lizard-cuckoo_(Coccyzus_merlini),_cropped As I have stated before one of the strangest things to me is the ‘urban myth’ among many biologists that 10% of children exhibit misattributed paternity. In plain English, one out of ten fathers of any given child are not their biological fathers, though that is the social understanding. So this excludes children who were adopted and such. In general these are explicitly cases where the putative father is unaware that he’s been cuckolded. The 10% figure is a nice round number, and I regularly hear it in the public arena, but it is also surprisingly pervasive among academic scientists. A few years ago I was in a seminar where a behavioral ecologist alluded to the figure in passing, and being who I am I had to raise my hand and object that it just wasn’t the true. The researcher, who did not work with humans, was genuinely surprised at my objection, and didn’t seem to be particularly invested in the figure he gave, and was quite open to updating his beliefs about this issue. I experienced this again on Twitter recently, where a biologist casually referred to the 10% value, and I pointed to my 2010 post which leans heavily a on 2006 meta-analysis, which suggests values closer to 1-3%. Instead of being defensive, he simply acceded to the new information.

More recent work seems to have confirmed this finding: Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data. It seems obvious that a 10% rate of confused paternity is going to show up in a discordance between genetic and genealogical paternal lines. The authors of the above paper use two methods:

…based on an unbiased population-wide sample, the Y chromosomes of presumed patrilineally related males were compared with each other. Subsequently, EPP rates were estimated based on the discrepancy between the legal genealogy and the actual genetic relatedness. Second, the historical EPP rate within Flanders was estimated based on the genetic traces of a substantial past migration event from northern France to Flanders.


For the Flemish in Belgium the rates were 1-3%. Perhaps the Flemish in Belgium are unique, but that seems unlikely. There have been a reasonable amount of studies in Western Europe on this topic, and this is in line with other results. There may be cross-cultural differences though. But my bet is that in parts of Asia where there are long-term patrilineages, such as China or Mongolia, you’ll come up with a similar figure. The situation might be different in “small-scale societies,” and in particular those where women are primary economic producers, and not particularly dependent on male resources (these tend to be matrifocal societies, where agricultural labor depends on the hoe and not the plough).

But going back to the 10% figure, consider what it would mean if it was correct. In a random family of two children in about one out of five cases there’d be misattributed paternity in at least one of the families*. Most people have at least five close friends, so misattributed paternity wouldn’t be an abstract issue, it would be something you’d confront in your day to day life. Additionally, it seems unlikely to me that the chance of conception from affairs is going to be higher than within marriages, because many would take precautions in illicit relationships. So the proportion of sexual activity that is “extra-pair” is going to have to be rather high. Is that plausible? The major caveat here is that there are differences between population segments, not just across cultures. The rates for high status individuals seems very low. The rates for low status individuals seem rather higher. The 10% figure is actually not that implausible from samples which are skewed toward the underclass, which is often the case when you are looking at laboratory data uncorrected for background variables (i.e., the men who avail themselves of paternity testing services are not an unbiased sample of the population; they usually have something to worry about at a much higher rate).

The final conclusion is that we should be rather happy that the rates are likely far lower than 10%. A lot of work on extra-pair paternity has been done on birds, and here’s a paper from 2013, Faithful females receive more help: the extent of male parental care during incubation in relation to extra-pair paternity in songbirds:

Parental care provided by males occurs in a diverse array of animals and there are large differences among species in its extent compared with female care. However, social and ecological factors responsible for interspecific differences in male’s share of parental duties remain unclear. Genetic fidelity of females has been long considered important. Theory predicts that females should receive more help from their mates in raising the offspring in species with high genetic fidelity. Using avian incubation behaviour as a model system, we confirmed this prediction. The extent of male’s help during incubation increased with decreasing rate of extra-pair paternity across species (22 species of socially monogamous songbirds from 13 families; male’s share of incubation ranged from 6% to 58%), even after accounting for covariates, biases in species selection and intraspecific variability. Moreover, this result was not sensitive to two different phylogenies and branch length estimates. We suggest that our findings support the notion, backed by theory, that genetic fidelity is an important factor in the evolution of male parental care. We offer several behavioural scenarios for the coevolution between male’s share of parental duties and the genetic mating system.

The basic theoretical logic is pretty obvious. If cheating “pays,” then it will become ubiquitous until everyone becomes a cheater, and the social system will converge upon a new equilibrium. You can have low female fidelity and low male investment in family life, or you can have high female fidelity and high male investment in family life (assuming that the child-mother relationship is the core of a family), but exchanging the traits is probably not a viable long term proposition (see: Hippy communes, which tend to have short half-lives, or societies such as in the highlands of Papua, where males don’t invest much in offspring, but paternity is not a major social issue where sanction is ferocious as in other societies). High fidelity from females toward males who do not provide any resources or care of offspring seems irrational. And conversely, high male investment in offspring that are highly possible to be another male’s seems irrational.**

* Obviously it is unlikely that the events are independent probabilities, so there are more likely to be cases that both children being misattributed than one would expect from assuming that each child has a 10% chance of being from a different biological father.

** From an evolutionary perspective.

 
• Category: Science • Tags: Evolutionary Psychology 
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  1. Way off topic, but are you planning to review Nicholas Wade’s new book?

  2. post off topic stuff in the open thread from now on. in the future i’m just going to delete stuff off topic immediately.

    i have to read it, and i don’t have much time right now. so later.

  3. Nice post. You see these kinds of magic number statistics thrown around a lot in scientific talks and papers. After 20+ years, the original reference gets dropped but the number keeps going. Nobody is really wedded to the stat, but nobody wants to update the analysis either.

  4. I think you meant “fidelity” not “infidelity” here: “high female infidelity and high male investment”

  5. “You can have low female fidelity and low male investment in family life, or you can have high female fidelity and high male investment in family life (assuming that the child-mother relationship is the core of a family), but exchanging the traits is probably not a viable long term proposition[.]”

    In animals, often the only worthwhile legacy that a male can pass on to his apparent offspring is genetics.

    In humans, there is a much greater opportunity for a man to leave a cultural legacy distinct to him, even if this is not accompanied by a genetic legacy, and the existence of adoption of a phenomena across many cultures and eras suggest that many parents consider leaving a cultural legacy in children to be at least better than leaving no legacy at all, although not necessarily better than leaving both a cultural and a genetic legacy. In academia, it is customary for the relationship between a professor and the graduate students for whom he is an academic mentor and adviser to be conceptualized in just this way.

    Reactions men have to discovering that they have been cuckolded, at least from the anecdotal evidence that I have seen, can also be telling. Purported fathers who have perhaps paid child support to the mothers of these children but not shared a sustained intact family life with those children are often extremely outraged by this discovery. In contrast, fathers who have shared a sustained intact family life with these children are often more bemused and confused about how to feel, but tend to reaffirm their support for the parent-child relationship despite the discovery in this context with father and child alike often publicly stating that the person who raised the child was that child’s “real father” despite the absence of a genetic relationship.

    Similarly, much more often than not, when a man brings a woman who is pregnant with a child who is not his genetically, or a woman with young children into his life, and then has a long term stable household with those members, male involvement in child rearing is frequently just as great and just as sincere as in the cases involving a father and his genetic children, despite the fact that he has known about the lack of a genetic relationship all along. The biblical figure of Joseph, husband of Mary the mother of Jesus, rather than being a paragon of virtue to raise a child who is not his own, is actually acting the way that most men in that situation do.

    These anecdotes are perfectly consistent with a model in which leaving a cultural legacy in a child that one raised, while not preferable to leaving both a genetic and a cultural legacy in a child that one raised, is still viewed as an worthwhile success in life by the non-genetic but de facto father.

    In this case, the real tie breaking issue when it comes to male involvement in child rearing is not sexual fidelity per se, but is instead household stability. If a family where cuckoldry is present is also unstable as a result of problems in the relationship that lead to infidelity in the first place, then the father has little opportunity to leave a cultural legacy to his purported child either. But, if the household remains stable despite cuckoldry, perhaps because it is not discovered and the relationship of the purported father and mother is mended, or perhaps because for whatever reason open sexual relationships are tolerated, then the link between fidelity and male involvement may be less intense.

  6. just google proximate vs. ultimate. that’s all you’re really talking about. culture is too broad and high level a phenomenon.

  7. I’m not sure I understand. If the males in a species spend more time cooperating with the female generally, as well as particularly during incubation, would the female have as many opportunities for infidelity? In other words, how do they show fidelity is causative, not simply a correlate to time spent together?

    Also, I’m not sure I understand the kind of selection under scrutiny. If it is sexual selection, for traits that might be deleterious to the species from a group perspective yet nonetheless advantageous for the reproduction of an individual, how can “cheating” pay for a female? And how could male parental investment lower reproductive fitness in general?

    But if we assume that more or less monogamous pairs have a reproductive advantage, why do we have such a wide disparity in percentages of male support? It comes to mind quickly enough that some species may face ecological pressures, some more severe. In the species facing more severe conditions, pairs raising offspring have the reproductive advantage. Wouldn’t the wide range of results be due to the wide range of environments, rather than female fidelity?

  8. Jason says:

    Given the extreme costs of cuckoldry, an important question arises: why do some males seem not particularly concerned about it? Perhaps you could tell me if I’m close to the answer:

    As you mention, in some societies “paternity is not a major social issue where sanction is ferocious as in other societies”. The typical male strategy in such cases is to invest in one’s sister’s offspring, because the genetic link is guaranteed. So, whatever the root cause of an r-selected society filled with promiscuous women, the result reliably seems to be less male investment in any given woman and her offspring. This defangs cuckoldry.

    Now, a recent study* argues that “high value” males exhibit greater anger/jealousy to their partner’s sexual infidelity compared to a lower value male’s response. (Consider the cuckoldry fetish; a fair assumption is that such men are low value and not particularly desired by the opposite sex).

    This may partly explain the subsection of males who appear to exhibit little opposition to female promiscuity (and by extension, the threat of cuckoldry). Taken in total, would it be fair to say that those males most opposed to “slut shaming” or opposed to judging a woman for her sexual history (think male feminists) are typically low value males (perhaps “beggars can’t be choosers” and they’re trying to get sex through the tactic of nonjudgmentalism) *and* males (whether high or low value) who live an r-selected type of lifestyle who don’t invest long term in any given woman.

    The genetic costs of cuckoldry are so extreme that I think this is an important question.

    * It’s summarised here by Gad Saad: http://www.psychologytoday.com/blog/homo-consumericus/201404/how-your-mate-value-affects-your-responses-infidelity

  9. why do some males seem not particularly concerned about it?

    1) not everything is adaptive on the individual level. there’s noise, and frankly developmental issues (a lot of ‘fetishes’ seem like psychological misfires)

    2) So, whatever the root cause of an r-selected society filled with promiscuous women, the result reliably seems to be less male investment in any given woman and her offspring. This defangs cuckoldry. r vs. K selection not really relevant to human societies.

    3) Taken in total, would it be fair to say that those males most opposed to “slut shaming” or opposed to judging a woman for her sexual history (think male feminists) are typically low value males (perhaps “beggars can’t be choosers” and they’re trying to get sex through the tactic of nonjudgmentalism) *and* males (whether high or low value) who live an r-selected type of lifestyle who don’t invest long term in any given woman. in such complex systems logical inference like this tends to have low predictive value in my experience. you could make a post facto argument about how high status males oppose slut shaming because they’re the ones who get all the female attention, and they want to maximize it without support.

    If the males in a species spend more time cooperating with the female generally, as well as particularly during incubation, would the female have as many opportunities for infidelity? In other words, how do they show fidelity is causative, not simply a correlate to time spent together?

    lots of studies look at birds since male-female cooperation and monogamy are the default. so you look at variation in ‘extra-pair’ matings.

    for traits that might be deleterious to the species from a group perspective yet nonetheless advantageous for the reproduction of an individual, how can “cheating” pay for a female?

    generally stupid to talk about ‘from a group perspective.’ do you know any evolutionary genetics?

    But if we assume that more or less monogamous pairs have a reproductive advantage, why do we have such a wide disparity in percentages of male support?

    who assumes that? i don’t. don’t assume your assumptions are shared.

    your whole comment implies that you need to learn some evolutionary genetics to clarify your models. i’d suggest smith’s evolutionary genetics.

    usually a good idea to not speculate too much about a domain where you don’t have much specialized knowledge.

  10. “just google proximate vs. ultimate. that’s all you’re really talking about. culture is too broad and high level a phenomenon.”

    I see how you could conceptualize it that way, but my core point is that in human societies memetics can be as important as genetics.

    Humans often act in ways that undermine genetic advantage in order to advance there memes instead. Indeed, given the dramatic pace at which our “memone” has evolved since the Neolithic, relative to the pace at which are genome has evolved, it is fair to assume that selection on memes in human interactions have tended to be much more intense than selection on genes in humans for most of the last several thousand years.

    The Uralic Magyars who brought to Hungarian language to Hungary, for example, very successfully propagated their language and cultural norms, both of which can be conceptualized as being made up of memes, extremely successfully, even though their own genetic descendants received little or no benefit from this activity. Their race may have stagnated, but their way of life was fit and did survive.

  11. I see how you could conceptualize it that way, but my core point is that in human societies memetics can be as important as genetics.

    your point is irrelevant and superfluous. you don’t need to bring in culture at all into it explain the motivations of these men. a behavioral ecologist can explain it easily in an evolutionary context. similar sorts of ‘non-adaptive’ behavior in the animal world exists.

  12. I see I was over elaborate.

    How is “cheating” ever beneficial to a female?

    And how can male parental investment lower a male’s potential for extra-reproduction so much that a male who cheats on investment wins the majority of extra-pair reproductive encounters?

    (Phrasing that colloquially, how does being a dead beat dad mean you are more attractive, so that you are the one with the secret harem…instead of all you guys raising each other’s bastards?)

    I was asking which variations in extra-pair matings show that genetic fidelity is a causal correlate, and how they rule out any the possibility of undiscussed factors causing both genetic fidelity and male investment to correlate?

    And now I’m confused about why monogamy is the default if it isn’t advantageous?

  13. How is “cheating” ever beneficial to a female?

    get better genes in the sperm donor, but an overly solicitous male as the caretaker. another model is that *some* cheating or extra-pair mating invests other con-specific males in your offspring, because there is a probabilistic model of fatherhood (this actually occurs among the ache natives of south america, where weak monogamy results in distributed perception of fatherhood, so more males are invested in one child).

    And now I’m confused about why monogamy is the default if it isn’t advantageous?

    it’s not the default in mammals. it is in birds.

    there’s a huge literature on this. i’d suggest you just look it up. your questions are hard to understand partly because you’re going blind without a framework.

  14. Very small sample but better than anecdotal. I’m part of National Geographics family genome project. They match Y chromosomes to surnames to track migration. I have 35 matches that go back 5 or more generations and only one mismatch, well under 1%

  15. 30%. Well, anybody comments on that?

    men who submit to paternity tests are not a random sample of men. they have reason to be worried (and interestingly, even in these cases most of the time they’re suspicions are unfounded).

  16. Anonymous • Disclaimer says: • Website

    Right on the spot!! I totally agree you that men who submit to paternity tests are not a random sample of men. Just the opposite. They are way brighter that the usual men (cuckolds included) representing a highly specific category namely those who distrust women.
    Now, on a more serious note, it’s about those men whose suspicions turned out founded. That 30% percent has been persisting for several decades. Any statistician around here capable of reading my mind? 😉

  17. 30% percent has been persisting for several decades. Any statistician around here capable of reading my mind

    correlating surnames and Y chromosomal lineages implies that the real cuckoldry rate is ~2%, not 30%.

  18. @David Webb
    “I totally agree you that men who submit to paternity tests are not a random sample of men. Just the opposite. They are way brighter that the usual men (cuckolds included) representing a highly specific category namely those who distrust women.”

    Actually, the another consistent finding from the literature is that the more intelligent men, the less likely he is cuckolded. The ratio of paternity uncertainty is way lower in the upper echelons of the society than in the lower.

    Don’t be the victim of the confirmation bias 🙂

  19. Jm8 says:

    Hoe agriculture is not always so strongly associated with female farming.
    In large areas of Sub saharan West Africa, much of the farming was traditionally done by men(though sometimes with women farming a supplementary crop) This includes most of Nigeria, Ghana, large parts of Mali, Senegal and the general Western Sahel/Savannah region.) This area was ascribed to what some early scholars like Hermann Baumann called the “higher hoe culture” and sociologist/scholar of sociobiology Stephen K. Sanderson calls “intensive horticulture”, intermediate in cultural complexity between primitive hoe cultures/horticulture and advanced plough cultures. Often in Advanced horticulture, fallow peroids tended to be shorter than in certain other hoe farming regions because of the land’s greater fertility and men have a greater role in farming. In this system it is more common for cultivated plots rotate within a permanent area, aka rotated bush fallow, often owned by an extended family(as opposed to a more mobile shifting horticulture, with fallows reverting to tribal tenure and rarely used again. Most of Polynesia, parts of Micronesia had Advanced horticulture as well

    The so-called female farming area in Africa, was mainly in Central Africa south from the Congo region. Even there men often had important subsistance roles which varied by ethnic group and location(See the work of the ethno linguist Jan Vansina on early Central African cultures, such as his book, “Paths in the Rainforests” which covers early subsistence), usually clearing the land for planting(clearing is more frequent in places with longer fallow periods), planting seeds/yams, and building and maintaining field fences (also houses and most other structures). They also hunted and fished, which supplied most of the protein. They were usually responsible for tending the oil palm whose oil and palm-wine (and sometime other products) were part of the general diet.
    Jane Guyer’s work on the precolonial farming systems of various, Central, and a few West African tribes showed sex roles were fairly complex often with several tasks performed by each sex, and the roles of men in farming usually greater in earlier times.
    See:
    “Female Farming in Anthropology and African History” by Jane Guyer

    http://books.google.com/books?id=GGomG4fhU5gC&pg=PA257&lpg=PA257&dq=female+farming+jane+guyer&source=bl&ots=ysTsujoh4a&sig=m39KUZ0UgrgX9ocNJMJ4vxPHvCE&hl=en&sa=X&ei=6hxrUNGFCavh0wGEjYFY&ved=0CEYQ6AEwBQ#v=onepage&q=female%20farming%20jane%20guyer&f=false

    According to Guyer and others, the agricultural role of men in some areas was weakened somewhat in more recent times by the introduction of new crops like cassava, because among other reasons it was considered a womens’ crop, being easier to grow than older crops. Relatively lucrative wage labor in the colonial period also caused men to be away from home for long stretches in some places.

    http://books.google.com/books?id=7FwOsfQDFWoC&pg=PA206&dq=female farming guyer&hl=en&sa=X&ei=d-d2U43FKo2wsAT_4YDwDA&ved=0CEsQ6AEwBg#v=onepage&q=female farming guyer&f=false

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