Non-Paternity, or the Interloper Rate

August 7, 2012

Over at the Salon, a Dear Prudie column discusses the issue of miss-attributed parentage.

My husband was estranged from his parents for many years. He reached out to them when he was diagnosed with a terminal illness. They didn’t have enough time to discuss and resolve their past, but they were at peace with each other when he died. Now my husband’s parents wish to keep in touch with me and my toddler-age son, as he is the only link they have to their only child. The problem is that my son is not my husband’s biological child. I had an affair

So the interesting part here is the growing trend for personal genetic services such as 23 and me. Among other things that you can do with 23 and me is to identify possible relatives in their database. As in, strangers who you don’t know are related to you, perhaps as closely as a 2nd or even 1st cousin (yikes). You might also have known family who are also 23 and me users, of course.

See where we’re going with this?

A simple search for nonpaternity on PubMed pulls up some interesting studies.

Wolf et al 2012 used human leukocyte antigen (HLA) typing to estimate a nonpaternity rate of 0.94% in a sample of 971 German children.

Voracek et al, 2008 conducted a meta-analysis of 32 published samples from 1932-1993 and identified a decline in nonpaternity over time. The mean and median rate was 3.1%, btw.

Li and Lao, 2008 and Lucast 2007 discuss the ethics of discovering nonpaternity during medical screening and research studies. These types of works touch most directly on the Dear Prudie issue, I reckon. The 23 and me era presents interesting new possibilities. There is no longer any professional “genetic counselor” intermediary or paternalistic physician deciding whether to “tell”. People might find each other more or less automatically and contact each other through the 23 and me website. But, and here’s the rub, the information propagates. Let’s assume there is a mother who knows she had an affair that produced the kid or a father who impregnated someone unknown to his current family. Along comes the 23 and me contact to their child? Grandchild? Niece or nephew? Brother or sister? And some stranger asks them, gee, do you have a relative with these approximate racial characteristics, of approximately such and such age, who was in City or State circa 19blahdeblah? And then this person blast emails their family about it? or posts it on Facebook?

Williams 2005 shows how paternity can affect major societal knowledge such as the infamous Jefferson/Hemings case.

Cerda-Flores et al 1999 found a 8.1% interloper rate but discuss the issue of being able to exclude fathers based on blood group systems. The very earliest literature on PubMed clearly focused on these issues, i.e., how to use the available imprecise markers to come up with statistical probabilities. The new era of personal genetic identification presumably improves substantially on these issues.

There are more articles and you can scan them for yourself. But I’ll end on two key notes. First, clearly this is a nightmare issue for people who are looking into rare genetic variants that are related to disease because the familial patterning is so important. It is critical to know who the father really was to keep the dataset valid and clean. Second, there seems to be a rumor of 10% nonpaternity that floats about in the literature, perhaps as a lasting straw argument or from some early flawed dataset. What the more recent studies seem to conclude is that this is an overestimate.

Or, you know, you could just read Dear Prudie’s response which includes:

But I don’t think your late husband’s parents need to hear this. … And I don’t see any reason to deprive your child of a potential inheritance.

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No Responses Yet to “Non-Paternity, or the Interloper Rate”


  1. Am I just fucken drunke, or did you post on this shitte before?

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  2. drugmonkey Says:

    The former

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  3. RedneckRootsKeepKnippingAtMyHeels Says:

    I’ve said repeatedly that I’ll never trust my family tree. Not only is it all loops and twists and shitte just a few generations back (rural Kentucky), but there are so many goddam lies in my family about *maternity* let alone paternity.

    – cousin who was raised by her aunt w/o her knowledge. didn’t find out until family fessed up after her “aunt” (actual mom) died by getting high and passing out face first onto a radiator
    – she’s now in federal prison for drugs or something & family is lying to her daughter about her mom
    – aunt was lied to by her mom about her father. said he died in car accident, but actually divorced. she didn’t find out until 40+ and he was already dead from cancer
    – then she lied to her daughter re: her father. told her that she had same estranged father as her half-brother. didn’t disclose until she was a teenager
    – plus, even more hush-hush family gossip of similar bullshit with 2nd & 3rd cousins, etc

    So I take everything re: parentage in my family w/ a huge-ass salt lick. In most of these cases, people found out eventually, but I suspect 23andme could help move that process along.

    No doubt non-paternity rates are higher than non-maternity rates, but I *do* wonder how they compare generally.

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  4. whimple Says:

    There is no need to put the term “genetic counselor” in quotation marks; it is a totally legitimate profession.

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  5. DrugMonkey Says:

    I had a bad experience with one whimple.

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  6. Pascale Says:

    As a doctor who evaluates relatives as kidney donors, you would be surprised at the relationships or lack thereof.
    In my opinion, if a dude has raised a child and been in the home, he’s the father. Nurture trumps genes unless organ donation is involved. And I never out “nonparents”

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  7. I had a bad experience with one whimple.

    The first time I saw you I was all like, “Dude, you look like motherfucken genghis khan!”

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  8. Juniper Shoemaker Says:

    Let’s assume there is a mother who knows she had an affair that produced the kid or a father who impregnated someone unknown to his current family. Along comes the 23 and me contact to their child?

    23andMe doesn’t require users to publicly disclose information beyond their haplogroups and the degree to which they’re related to other users in terms of percentage of genome shared. Obviously, this doesn’t make your scenario improbable. I thought your readers should know if they didn’t already, though.

    Second, there seems to be a rumor of 10% nonpaternity that floats about in the literature

    That’s funny. This isn’t “the literature”, but Jared Diamond wrote about this once. If I remember right, he said he knew a physician who tried to conduct an ABO blood type study involving babies born to affluent white parents during the 1950’s. The physician wound up too shocked and embarrassed to publish a bit of it because ~11% of these babies couldn’t have had the fathers their birth certificates claimed.

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  9. Busy Says:

    Pascale can you give a ball park figure? I’ve seen layman articles claiming a non-paternity rate as high as 30%, but every time I see a serious academic paper on the subject it is more like 1-3%.

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  10. Jonathan Says:

    I think you’ll probably find a number in here, can’t check at the moment as I’m not behind the pay wall ATM. http://onlinelibrary.wiley.com/doi/10.1111/j.1748-720X.2008.00271.x/abstract;jsessionid=09D1BA10E8C7B1F32F842DEB82192C79.d01t02

    It should be noted that non-paternity is the most common incidental finding researchers will come across.

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  11. Gerlag Says:

    If you put your genetic information and contact information out there, you need to be prepared for the ramifications.

    I’ve heard some groups argue that there should be compulsory paternity testing with child birth when the father is going to co-parent. A birth certificate is a legal document that is often created under duress and based on the mother being truthful. A man listed on the birth certificate may unwittingly provide and be legally required to provide support for a child that is not his for decades. Given the decreasing costs of paternity tests, and the ability to determine paternity from blood tests during early pregnancy (http://www.nytimes.com/2012/06/20/health/paternity-blood-tests-that-work-early-in-a-pregnancy.html?pagewanted=all), I predict that this will happen in the future.

    This will be a death knell to Maury Povich because he won’t be able to have his “are you the baby daddy?” shows.

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  12. Jonathan Says:

    @Busy – from the references in the Wright Clayton article, this paper might be what you’re looking for: K. G. Anderson, “How Well Does Paternity Confidence Match
    Actual Paternity? Evidence from Worldwide Nonpaternity
    Rates,” Current Anthropology 47, no. 3 (2006): 513-520

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  13. A birth certificate is a legal document that is often created under duress and based on the mother being truthful. A man listed on the birth certificate may unwittingly provide and be legally required to provide support for a child that is not his for decades.

    Yeah!! First those fucken lying bitchez steal our sperm, and then they steal our money!!

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  14. Szescstopni Says:

    I was asked in the early 90s by a geneticist to help with porting a program that was supposed to pick up genetic problems in families (grandparents included) from i286 to a newer processor (i386). We went through the code. On seeing a line that printed “impossible mutation” I asked what was going on. The answer was simple. “The father is not the one in the papers. Here in Poland that’s something like 10%. Same in France. In England it gets to 30%”.

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  15. Busy Says:

    “The father is not the one in the papers. Here in Poland that’s something like 10%. Same in France. In England it gets to 30%”.

    Another example of the 30% figure thrown around without any basis. I think it comes from “30% of all cases where there was suspicion of non-paternity to begin with” study which is mentioned in the second article by Jonathan (thanks for the ref btw).

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  16. […] the 23andme genetic screening service in the context of their belated adoption of IRB oversight and interloper paternity rates. You may also be interested in Ed Yong's (or his euro-caucasoid doppelganger's) […]

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