"Inadvertent" incest detection?

By Razib Khan | February 11, 2011 11:12 am

Ruchira and Randall Parker point me to a new story about routine genomics screens detecting first degree incest:

Beaudet wrote in the letter that “clinicians uncovering a likely incestuous relationship may be legally required to report it to child protection services and, potentially, law enforcement officials” since the pregnancy might have occurred “in the setting of sexual abuse.”

The letter was prompted by a Baylor laboratory’s discoveries that developmental disorders in a number of pediatric patients were caused by incestuous relations not previously disclosed to doctors.

The testing is done to find the disorder’s genetic basis, typically involving mutations, deletions or duplications. But large blocks of identical DNA are evidence the child’s parentage involved first-degree relatives.

If you’re curious if you are the product of incest, David Pike’s runs of homozygosity (ROH) detector (Mozilla only) might be useful if you have a genotype file. Sometimes I wonder if mass technology is going to come to fruition far earlier than it takes to write up editorials and publish them.

Of course even people who are not the product of first-degree incest can have very long ROH. Look at Zack (though is in part a legacy of the consanguineous marriage practices common in his parents’ community). And there will be many people who are going to get their siblings typed (as I did), so amongst the intelligent set cuckoldry, rare as it is, will be exposed.

CATEGORIZED UNDER: Genetics, Genomics

Comments (9)

  1. Georg

    Much more “interesting” will be proofs or disproofs
    whether someone is father or not of some child.

  2. I am actually really curious about how many people end up marrying half-siblings, given the normalcy of adoption, as well as sperm and egg donation. Blood tests used to be required for marriage licenses– I wonder if there will be a push for DNA tests from conservatives?

  3. I wonder if there will be a push for DNA tests from conservatives?

    why would you say conservatives? (just so you know, i identify as conservative)

  4. “Much more “interesting” will be proofs or disproofs whether someone is father or not of some child.”

    In Colorado, DNA evidence is not conclusive on the question of paternity. More than five years after a child is born, the presumption that a person married to the child’s mother is the father of the child is binding and conclusive, notwithstanding DNA evidence to the contrary.

    Also, genetic parents have no special preference in parenting time and parental responsibility decisions within a “best interests of the child” analysis that can also include any people in “possession” of the child, and people who have spent substantial recent time with the child (e.g. step-parents or extended family).

    Basically, our jurisprudence has very deliberately decided that fatherhood (and motherhood), in law anyway, is a psychological bond that often concides with but is not determined by genetic relatedness. A father is someone who has acted like a father, not necessarily just a sperm donor.

    Similarly, in the area of assisted fertility, we look to the intent of those involved rather than genetic relatedness.

    Generalizing concepts like parent on a non-genetic basis (and mostly a gender neutral basis) has made this area of the law rather more complicated than it was in the “good old days” but it has also provided considerable stability as technology and social norms evolve.

  5. pconroy

    I think genome testing at birth or more likely in utero, will be the norm in 10 years.

    As it is, my newborn was part of a pilot study to detect over 80 different genetic conditions – such as Fragile X and micro-deletions – in utero. This was because of my very rare Tay-Sachs mutation, we were flagged as being study eligible.

  6. Roger Bigod

    This is a special case of “nonpaternity”. The best estimate of frequency in the English population was done on a family named Sykes. The name was adopted in one small area, and the adoption period was 1-200 years after the Conquest. But only half of a sample of males with the surname carry the index sequences on the Y chromosome. The others are random, consistent with multiple nonpaternity events rather than a second founder. Using this data, the investigator (incidentally named Sykes) estimated a nonpaternity rate of 1.3% per generation. I don’t recall if the paper mentions a policy on informing subjects.

    The issue came up long before sequencing was possible. Human “blood groups” are (glyco)proteins on the surface of red cells that have a clear Mendelian inheritance pattern. There are about a dozen common blood groups and most of them were worked out by some industrious British blood bankers in the 1940’s and 50’s. The procedure was to collect blood from many members of a large family and check the known blood groups to establish paternity. Then they could eyeball a pedigree chart to find a Mendelian pattern.

    In the course of these studies, non-paternity turned up in a small but noticeable fraction of the families, consistent with Sykes’ frequency estimate. They elected to quietly drop such a family from the series, without telling the subjects. It’s a reasonable decision, although one could think of examples where informing the subjects would be beneficial.

    (My information is word-of-mouth from a blood banker who knew some British blood bankers from professional meetings and courses.)

  7. Oh boy, what searches would lead to my blog now! 😉

  8. Roger Bigod

    I checked your link to a discussion of nonpaternity, and I see you have the Sykes data already. The blood group work may be the first time that investigators had to set a policy on informing subjects.

    Your discussion of surnames seemed a little unclear. The way it happened was actually favorable for quantitative conclusions on a name like Sykes. Before about 1150 nobody in England had proper surnames in the sense of modern usage. After about 1300 everyone had one. The names are either locative, occupational (e.g. Carpenter, Mason) or paternal (e.g. Robertson, Anderson).

    One complication is that place names were used by the upper strata to mean ownership of land in the area, or of the local manor house. Some of these became surnames. This adds only a century or so of uncertainty in estimating chances of nonpaternity.

    Another departure from the rule is that some Norman names persisted. The Corbett family produced a Sheriff of Shropshire county in the late 20th Cent., descended from a Roger Fitzcorbett who was 18 at the time of the Conquest and probably took part.

    I don’t think these considerations apply to the Sykes family. There is a reasonable sample size and the distribution of the name is still highly circumscribed, so it’s good estimate of the rate of nonpaternity for a rural setting in England. It would be interesting to know if the higher rates are for urban populations.

  9. A court rejected blood type evidence from Charlie Chaplin when he was accused of fathering someone‘s child, so requiring paternity payments despite DNA tests isn’t that surprising.

    Robin Hanson describes the status quo as a conspiracy against cuckolds. Many of his students think that the husband is at fault if his wife goes outside the marriage.


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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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