I ran across this image attached to a rather vitriolic post (the thrust of which was, in essence, “only stupid inbred hicks oppose gay marriage and this map proves it”), but it struck something of a thought process. Here goes.

First of all, the map’s not entirely accurate with respect to what the author was trying to say. Five states, at least, shouldn’t be listed as “allowing” cousin marriage, since their restrictions make it so that an impossibly small portion of their population will realistically participate. There’s a considerable overlap with gay and cousin marriage allowability in the northeastern section of the US. And of course the Granola State on the west coast, a place which carries almost entirely the opposite of the “inbred hick” stereotype, allows cousin marriage and has gone back and forth on the issue of gay marriage for a few years now.

Secondly, the science against cousin marriage is muddled. The usual argument put against it is that it encourages genetic diseases. In certain populations, specifically populations where cousin marriage is encouraged and founder effects come into play, this is true. Small, isolated rural villages of current/past ages, the inbred lines of European royalty, and the lines of fundamentalist Mormonism come to mind here. Another example is the Dutch settlers to South Africa (the “Afrikaners”), who carry magnified risk of Huntington’s Disease because an abnormal percentage of the original settlers were carriers.

On the other hand, research into larger, more diverse genetic populations indicates that “once in a while” cousin marriage carries relatively small risk – about the same risk as a woman having kids at the age of 40 rather than 30. The further argument is that laws against it in the US were motivated not by risk of genetic disease, but by a desire to force immigrants to intermarry into the population (and thus assimilate) in a quicker manner.

Oddly enough, the argument about “inbred hicks” falls apart when comparing the map of European gay marriage laws. I’d put a map up comparing it to European laws about cousin marriage, but there’s no real point to it: cousin marriage is legal in 100% of Europe. Two countries have recently begun discussing the option of banning it, and oddly enough, it’s not even the condition of their oddly buckteethed/colorblind/hemophiliac (that last being the origin of the term “blue-blood” as a reference to royalty) royal lines that did it, but rather the high rate of genetic diseases in recent immigrant populations from the rural sectors of Islamic countries, who perpetuate societal cousin marriage rates of 55% or above in a population where it’s not uncommon to be the child of a chain of 8-10 cousin marriages (including “double cousin” marriages, wherein the kids are not simply cousins but where mother/aunt and father/uncle, or mother/uncle and father/aunt, constitute sibling pairs as well making the kids almost genetic siblings) in a row.

The trouble with this is discussion that it’s a perfect example of a “where do we draw the line” sort of argument. On the one hand, in a (mostly healthy) genetic population where cousin marriage would be rare and genetic diversity a given, arguers against cousin marriage would quickly expire upon the line of “well why do we let 40-year-old women have kids then?” On the other hand, we have definitive proof of the genetic risks of allowing multigenerational cousin marriage. There even comes the risk that at some point, society could start stopping non-sibling people from marrying because they both carried a recessive gene for some debilitating genetic disease like Huntington’s or Tay-Sachs, or even something as merely inconvenient as Celiac. It’s not that farfetched; some states to this day still require a blood test, a holdover from times when they were screening for sexually transmitted diseases such as syphilis. Another justification (now that the technology exists) for genetic testing as a marriage requirement could be to ensure that they aren’t unknowingly marrying their half-sibling or even full sibling, due to the high percentage of absentee/unknown fathers or potential for siblings to be separated too early in life to remember each other in certain populations.

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7 Responses to Kissin’ Kin

  1. Transplanted Lawyer says:

    Argument: “Gay marriage will lead to legalized incest, like marriage between cousins or siblings.”

    Opposition: “No, it won’t, and even if it did, so what?” (Include link to this article.)

  2. web says:


    That’s not the point of this article, and I’m sure you know it. Further, gay marriage itself is on the “not even with a 40 foot pole” list of discussion topics for HC because of the level of vitriol it brings. Please drop that line of discussion.

    The post was posited for its relevance regarding the question of prohibiting cousin marriage for its genetic risks, as opposed to the thought of actually requiring genetic testing for either the blocking of certain marriages or the requirement that people in certain marriages refrain from procreating due to the risk of passing on debilitating genetic diseases.

    Part of the problem is that it is such a matter of degrees. In a normal society in which cousin, “double cousin”, or even sibling marriage is a relative rarity (though we kind of have to assume it happens a bit more occasionally in certain US populations merely because of the number of children with no clue of their male parentage, weirdly done in this House episode), the occasional cousin marriage seems to pose no problem. The tighter the genetic pool and the more permissive the society of cousin marriages, however, the worse the risk gets (thus the case studies from above).

    If anything, the case studies of European royalty and the insular villages of “traditional” cousin marriage from backwards regions like rural Pakistan give us an indication why, even though the risk may be small “in an individual case in a western society”, starting down that road may not be the best thought. Will doesn’t like “slippery slope” arguments, but considering the way in which cousin marriage amplifies risk over time, it does seem to be a decent case for such a scenario – provided the argument can be made that making cousin marriage legal would result in enough cousin marriages going 2-3 generations deep to pose a significant problem.

  3. kirk says:

    I’ve always wondered: what is the difference between “first,” and “second” cousins? Also, I’d like an explanation of “double” cousins, as I’ve never heard the term before now.

  4. web says:


    there’s a whole set of terms to describe how you’re related to someone.

    In essence (beginning from closest, and going to furthest away:

    1 – Brother/Sister.

    2 – “Double Cousin.” When your grandparents are first-cousin related sets. Essentially, happens if your grandparental sets were ALSO cousin marriages. DNA-wise, you’re about as closely related as a brother and sister.

    3 – First Cousin. You share two grandparents (and only two) with them.

    4 – Second cousin. You share two great-grandparents with them.

    It goes on and gets more complicated (“degrees of removal” denote generational differences for instance – your first cousin’s children are your “first cousins once removed”). But that’s the general structure.

    Generally speaking, second-cousin marriages are not even blinked at, though the Church back in the 12th century had briefly extended the prohibition all the way out to 6th cousins and even through “by marriage” cousins (caused when you actually have no blood relation to someone, but instead are related because of divorce/widowing and then remarriage). They gave up on it when they figured out that they were going back 6-7 generations on the family tree and it turned into a “Six Degrees Of Kevin Bacon” scenario.

  5. Nanani says:

    Cousin marriage prohibitions are not about genetic diseases, and I would wager they never have been. The fact that there were prohibitions on it before genes were understood makes this rather plain.

    It is a social issue, a fundamental one. Societies with high levels of cousin marriage (such as the 55%+ quoted for rural islamic immigrants) are low-trust societies with family loyalities and clan warfare swamping nation-level concerns and being generally conducive to a nasty state of affairs.

    So, there is no reason to ask why women over 40 are “allowed” to have children. The government is not in the business of regulating who has children. It is, however, in the business of promoting harmonious social arrangements, and cousin marriage is inimical to that.

  6. trumwill says:

    “Double Cousin.” … Essentially, happens if your grandparental sets were ALSO cousin marriages. DNA-wise, you’re about as closely related as a brother and sister.

    I thought “double cousins” are when two sets of siblings marry one another (ie you have two brothers from one family marry two sisters from another) and don’t have anything to do with cousin marriages of the grandparents. The grandparents would be the same people. That’s always been my understanding of the term.

  7. Maria the Lurker says:

    I don’t believe that the hemophillia of European royalty in the late 19th-early 20th century was related to cousin marriage. The hemophillia carrier gene was passed to Queen Victoria by her mother, and she in turn passed it on to two of her daughters and many of her 20+ grandaughters. These female descendants of Victoria then married into most of the royal houses of Europe, and the disease started to appear amongst their male descendants, the most famous being the doomed Alexei, the last czarevitch of Russia, who was a great-grandson of Victoria. Curiously, one of Victoria’s sons, Prince Leopold, who died of the disease in his early 30s, apparently passed the carrier gene on to his daughter Alice, who had a hemophilliac son. Normally males do not pass along the gene, only females.

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