Our forefathers were fierce & our foremothers were faithful

By Razib Khan | October 27, 2013 8:51 pm

Credit: Chineeb

Credit: Chineeb

One of the peculiarities of human historical genetics is that people can simultaneously accept the existence of aggressive polygynous males such as Genghis Khan, and promiscuous females who give rise to the idea that 1 out of 10 children have an incorrect assigned paternity. I’ve mentioned the cuckoldry myth before. It is a common evolutionary myth; I’ve heard many biologists quote the 1 out of 10 number, and have often made myself obnoxious by pointing to the contradictory literature in this area. This isn’t to say that cuckoldry doesn’t exist. There’s certainly an evolutionary reason so many males engage in “mate guarding.” But you don’t need a high frequency of a trait to allow it to be selectively constrained. If it’s deleterious, then it will be driven down in frequency rather quickly. Whenever you get outbreaks of males who are sanguine about providing resources for offspring who are not their biological issue, natural selection will kick in and guarantee that this generous spirit toward their cheating partners and the delinquent cads does not persist.


The way that modern genetics adds value to this area is that one can compare Y chromosomal lineages to surnames. The logic is simple. If you have a constant frequency of misattributed paternity per generation over time the correlation between a surname and a Y chromosomal lineage will weaken. In addition, because the interlopers are likely to be different from each other you’ll have a pattern with (for example) ~50% of the male individuals of a given surname may carry one haplotype, while the other ~50% are distributed across hundreds of other haplotypes (one can imagine twists on the scenario, for example an early interloper might result in a secondary highly frequent haplotype).

So here’s an new study to bury this tired old urban myth, Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data:

Overall, our results provide the first large-scale, unbiased genetic study of historical EPP rates in a human Western European population, with two independent estimation methods giving largely concordant results. Using the most direct estimation method, based on pairs of males that had a GCA in the last few centuries, we estimated the average EPP rate at 0.91% per generation (95% CI: lower bound 0.41% and upper bound 1.75%). This method took advantage of the hypervariability and mutability of Y-STR haplotypes, and the high phylogenetic resolution of the used Y-SNP haplogroups, which allowed paternally unrelated males to be easily recognized as such [35]. In addition, using a second method that was based on the population genetic traces of a past immigration event which happened at the end of the sixteenth century, we estimated the EPP rate at around 2%. Although this estimate had a broader CI (upper 95% confidence limit = 8%), the actual estimate was close to the first one.

Both of our methods therefore estimated a substantially lower historical EPP rate for Flanders than the 8–30% per generation suggested by previous studies based on behavioural data on rates of EPCs in Western Europe and given the absence of reliable contraceptive methods [30–33]….

It’s open access, so read the whole thing if you aren’t convinced.

The authors are clear that this is from a sample in Flanders, but I do not find that this population should be that exceptional across the Eurasian Ecumene. In other words, I’ll be willing to put down money that Indian gotras and Chinese patrlineal clans will exhibit the same pattern of cuckoldry frequency. Additionally, the authors note that this pattern of high paternity confidence is paired with male investment in offspring. That seems relatively typical among many members of our species, though the extent seems to vary by population and environmental condition.

CATEGORIZED UNDER: Evolution
MORE ABOUT: Cuckoldry
  • Douglas Knight

    It’s moot in the light of evidence, but I don’t understand your first sentence. Are you saying that a priori, aggressive polygynous males and (secretly) promiscuous females are not very compatible? that evidence for one is evidence against the other? I don’t see that one says much about the other.

    • razibkhan

      compare chimps 2 gorillas.

      • Douglas Knight

        Sorry, too cryptic for me. All I know about chimps and gorillas is from the PIN factsheets. They makes it sound like chimps have both more aggressive males and more promiscuous females. So that comparison suggests a positive correlation to me.

        But chimp females are openly promiscuous. I’m not sure what chimp cuckoldry would mean (though at least extra-group mating should count). You could say that chimps have male aggression but only gorillas have the possibility of cuckoldry.

        • razibkhan

          common chimps are poly (gynous and androus), period. females are open and cryptic promiscuous. gorillas are classically polygynous. humans are not analogous to any other ape, so comparisons are not good (i.e., look to be less polygynous than gorillas, but more than gibbons; chimps are orthogonal).

          in any case, my major point was that low male jealousy tends to correlate with low male direct investment. and vice versa (though in extreme cases of high male jealousy they go from mate guarding, to turning mates into de facto property).

          • Douglas Knight

            thanks.

  • dxie48

    From the Mongol myth, the distant female ancestor of Genghis Khan,

    http://en.wikipedia.org/wiki/Alan_Gua

    “Her older sons suspected their family’s Bayad servant to be the likely father.”

  • Brian Schmidt

    The study says they excluded adopted sons when the adoption is documented, but I’ll bet there are some that aren’t documented. At these low rates, that could be a decent chunk of what otherwise seems to be cuckoldry.

    • andrew oh-willeke

      Potentially related would be remarriage by pregnant widows that was not well documented.

      It would also be interesting to know what percentage of cuckoldry was secret v. instances like wartime rape which would have happened at fairly high levels during some episodes of the history of Flanders in the several century long time period that was studied.

      One also wonders if the Roman Catholic to Protestant transition that happened in that time frame in Flanders had any impact.

  • RogerB

    Genealogists refer to this delicately as a “non-paternity event”. Before the last 200 years or so, mortality in young adult males (fathers) was high and adoptions weren’t recorded, so the incidence may have been higher.

    There’s a study by an investigator named Sykes of a family with the same name. He came up with a 50% cumulative non-paternity over 700 years since adoption of the name, or 1.9% per generation.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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