How paternity testing is like international trade

Nonpaternity rate % N
Switzerland 0.83 1607
USA, Michigan, white 1.49 1417
USA, California, white 2.1 6960
USA, Hawaii 2.3 2839
UK, West London 3.7 2596
Paternity Testing Laboratories
UK 16.6 1702
USA, Los Angeles, white 24.9 1393
Sweden 38.7 5018
South Africa, Cape Coloured 40 1156

The results above are from Kermyt Anderson’s How Well Does Paternity Confidence Match Actual Paternity? This is still one of the best surveys of the field, despite being 12 years ago. A more recent paper, Cuckolded Fathers Rare in Human Populations, uses more powerful genetic genealogy methods to come to the same conclusion as Anderson’s survey: extrapair paternity, or nonpaternity events, are rare in Western societies. I don’t think it is limited to Western societies. I suspect that when high throughput sequencing is applied to Chinese clan lineages and Hindu gotras, you will found that nonpaternity events are similar to those in the West.*

On the other hand, in some small-scale societies, the rates are much higher.

I won’t delve into the evolutionary anthropology here. Rather, I want to point to a new paper, Growth of ancestry DNA testing risks huge increase in paternity issues. Ancestry testing is huge. Within the next year, it is almost certain that 10% of the American population when having some sort of high-density genomic testing done.

As the author of the paper pointed out to me on Twitter, 1% of 16 million people is still a lot. Yes, in absolute terms. But we need to look at the other side of the equation.

In Anderson’s original data one of the interesting results is that in most datasets drawn from paternity testing laboratories, where there is a very high suspicion of nonpaternity events, most of the fathers nevertheless were biological fathers! In a nonpaternity testing context, nonpaternity events will be much closer to ~1%. But, I think it is reasonable to suppose that some of the 99% of the fathers who turn out to be biological fathers also have suspicions…which are unfounded.

Like free trade, you tend to see one side of the equation much more than the other. In free trade scenarios, a minority of workers may lose their jobs or have to work under reduced wages, but the vast majority of consumers will get cheaper or better products. The former is much more salient than the latter.

Similarly, the small minority of fathers and families who are going to be “surprised” in a negative way, is balanced out by the likely larger number who have low-grade suspicions, but in fact, are confirmed in their biological relatedness.

Addendum: Needless to say, if you are part of the “cuckold community”, you should probably not getting this sort of testing.

* The necessity of good quality whole-genome sequencing is due to the fact that male relatives are excellent candidates for nonpaternity events. To get a certain estimate one would want to count unique mutations across the pedigree.

17 thoughts on “How paternity testing is like international trade

  1. This is kind of assuming that the doubtful fathers want to be reassured – many are potentially just looking for an excuse to bail on their biological children. Men pretty consistently treat stepchildren better than non-coresident biological children, paternity in and of itself isn’t the main trigger for parenting behavior.

  2. Like the Int’l trade analogy – although it is harder to tax the lucky ones here to help the unlucky ones in this case 🙂

    It would be interesting to see some correlations between the level of historical or contemporary paternal certainty with other variables (trust, GDP, property rights, gender equality, gender norms). It seems that political complexity definitely reduces nonpaternity events but I wonder if its because states provides something or is confounded by the same thing.

    I wonder if the malaise around family formation in low-income communities would decrease in a near-distant future where at ultrasounds, you get genetic information including paternity. Isn’t the nonpaternity event rate higher in lower-income families?

  3. It would be interesting to run genome analyses on the biological fathers in nonpaternity events to see what patterns there are in males with whom women choose to have affairs. But might need to wait for more detailed genetic findings first.

  4. The paper is paywalled and it’s hard to say if the cited studies might have suffered from the opposite bias of ascertainment (preferentially enrolling families without any paternity doubts). Such paternity “doubts” in modern society don’t necessarily involve secret cuckolding (secret from the legal father). More often, these could be undisclosed sperm-donor children or undisclosed in-the-family adoptions (no secret to the parents, but kept under wraps from the children) which would have prompted families to avoid enrolling in studies for the sake of protecting the weall-meaning secrets from the children.

    Also one would argue that divorce, contraception, and generally more equal female rates and the increase of love marriage, might have reduced the rate of illegitimacy in the XXth century (but earlier on, marriages of wealth and inequality would have been more susceptible).

  5. you can’t use sci-hub???

    anyway, the sample sizes on some of the western european ones get pretty large and i’m pretty sure there’s not an ascertainment bias. often the genetic stuff comes out of other types and studies and they then look at the Y and surnames or something.

    bryan sykes’ came up with ~1% 20 years ago using his rare surname and the sykes’ of england.

  6. Thanks, man! A great excursion to the age of pre-DNA genetics (almost all of the big studies used blood types, with the common goal being an attempt to demonstrate natural selection our species by observing differential offspring survival rates in different parental blood type combinations in different ancestries). Of course the papers of the 1950s through 1980s didn’t yet report how many of the subjects accepted enrollment and proceeded with complete blood typing of the trios. But Anderson 2006 is quite explicit that these studies “are likely to bias towards higher paternal confidence” due to non-random subject selection, married-couple filters, and use of trios.

    They didn’t quite know about batch effect biases / non-blinded review biases, too, but it may have been substantial, given that the most recent of the US bloood type studies, Ashton 1980, estimated that about 2/3rds of the observed trio mismatches were due to the technical errors of testing. I wouldn’t be surprised if the labs themselves tracked incompatibilities as a part of internal QC, and tried to resolve it before reporting. At least contemporary labs are very careful with trio result reporting for fear of exposing incompatibilities…

  7. I just found out the “Cuckold Community” was a thing. Thanks Razib, thanks Google.
    Now to go and wash my brain…

  8. The cuckold community is a bit like the people who refused to believe that the Princess Anastasia (daughter of the last Tsar of Russia) was really dead. Her aunt Olga, who realized on meeting her that the woman claiming to be Anastasia (Anna Anderson) was a fake, said, “My telling the truth does not do any good because people want to believe the mystery.”

    Many years later, DNA testing has proved Aunt Olga right – but I’m sure the mystery will continue in the minds of many.

  9. Razib writes: “In free trade scenarios, a minority of workers may lose their jobs or have to work under reduced wages, but the vast majority of consumers will get cheaper or better products.”

    Except when their are vast continental disparities in income and wealth, in which case a majority of workers (in the rich countries) may have to work under reduced wages. This is especially clear when there is also free international mobility of capital, when it becomes neoclassical economics 101. (Free mobility of capital, by the way, was never part of free trade theory — in fact just the opposite.)

    I know it’s not your field, razib, but this fundamental misunderstanding gets repeated too often.

  10. My little theory is that paternity testing will limit the reproductive value of extrapair paternity. Women who otherwise would engage in affairs may still do so but will be more vigilant to avoid pregnancy and childbirth because of the strong risk/near certainty of detection.

    The cuckolding, biological fathers no longer gain a reproductive advantage from their behavior. That could ultimately change the genome over generations.

    Granted however that the nonpaternity rate is pretty small, but even a percent or two could have a long term effect.

    The cultural issues that Razib raises are probably more important though. Memes trump genes, usually.

  11. Women who otherwise would engage in affairs may still do so but will be more vigilant to avoid pregnancy and childbirth because of the strong risk/near certainty of detection.

    So you expect people who engage in a risky behavior to do so vigilantly?

  12. Studies have generally found that non-paternity events are more prevalent in the lower socio-economic classes. And we have demographic data showing that – unsurprisingly – people on the margins of society have (up until recently) been much less likely to have children who survive to adulthood than the wealthy. Thus it’s likely that since the foundation of social stratification there has been at least mild selection against non-paternity, rather than in favor of it.

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