Cousin Marriage

Cecil's Columns/Staff Reports
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First post… not sure if this goes here, my apologies.

The Straight Dope answer on cousin marriage was woefully inadequate. It discussed cultural differences, the fact that European countries tend not to ban marriages between first cousins, and the idea that first cousins have only a marginally increased risk of producing genetically disabled offspring.

Okay, fine but that left out a bunch of important stuff:

  1. It is cultural, and the health statistics bear that out.

Countries and societies with high rates of first cousin marriage have far higher rates of genetic disease and disability. Why? Because when cousins marry, the family tree gets shaped weird, and within a few generations, all hell breaks loose.

For example, if two first cousins marry, have kids, and the kids marry first cousins, the real trouble starts with the grandchildren’s generation. Or, for another one, lets say two brothers both marry their first cousins, who are sisters, and a marriage results between the children of those families. Those kids are double first cousins- closer to being genetic siblings than they are cousins, and their children are much more likely to have health problems.

Or twins. Children of identical twins, are, genetically, half-siblings, though legally and culturally they are considered first cousins. (Or, if, for example the same man fathered children with both women in a set identical twins, those kids would be genetically full siblings. Or if identical twin boys married identical twin girls, their kids would be genetically full siblings.)

The point is this: cultural norms tend to last through multiple generations, and when offspring of cousins marry their own cousins, the rate of genetic disability is much, much greater than the general population.

  1. Right now in the UK (a European country, if I remember my geography) there is quite the movement afoot to ban first cousin marriage, because some of the immigrant cultures, for whom first cousin marriage is the norm, are really overtaxing the NHS due to all the birth defects within their community. For example, British Pakistanis make up less than 10% of the population, but represent 30% of the population disabled by birth defects. Google it.

  2. Genetic diversity is good for any population.

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Hi, Welcome to the Dope.

This is a good place for the debate you brought up, but as it appears you are commenting on this article, What’s wrong with cousins marrying? I have notified the moderators to move it if they think they should.

Two more somewhat related article you might want to read are

If twins marry twins, are the children from the two families cousins–or brothers and sisters?

What’s the term for your cousin’s children?

Jim

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I take it you are not from Shelbyville. :wink:

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Welcome to this MB. Don’t take this personally, but…

Can we have a cite that “all hell breaks loose”? Can you define what that means?

But how often does that actually happen?

How often does that actually happen?

The way things work around here is you produce a cite. You don’t ask other people to google it. The cite I’d be looking for is that these birth defects are known to be the result of inbreeding, and not some other problem-- like the fact that the immigrants don’t get as good prenatal care as the natives do.

No one will argue with that. Freedom is also good for people. The key is to find a balance.

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Had I to guess, I’d say societies that encourage cousin-breeding are ones that are (or until very recently were) extremely tribe- or class-conscious, in that the best way to keep track of who was “us” and who was “them” was to make sure “us” only mated wth other “usses” and “thems”, well… “them” is a bunch of wrong-worshipping heathens who’d best not pollute our noble “us”-hood in any case.

I always took it as a sign of societal health and enlightenment when one only had a vague idea of who one’s third cousins were, and thus less likely to vote alongside your third cousin in electing your fifth cousin to office (even if he’s a completely corrupt git) or going to war because your third cousin said we had to avenge some wrong that our tenth cousin did to our sixth cousin.

Rule of law is better.

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Okay, but their are dozens (thousands?) of websites dealing with the UK cousin marriage issue. Here’s one from the BBC. Feel free to do further research in the interest of balanced and thourough knowledge of the subject, hence my suggestion to make friends with Google.

As far as hell breaking loose and statistics regarding the prevalence of multi-generational consanguinity and its genetic consequences: I am not a geneticist. I am an epidemiologist. It is, to anyone with knowledge of human genetics, pretty obvious that recessive traits only express themselves after many generations of being merely carried. Consanguinuity short cuts this process by piling the same, familaily shared recessive traits on top of one another, especially over multiple generations. That’s what I mean by all hell breaking loose.

As far as how often cousins produce offspring who marry their cousins- that happens A LOT within communities who practice and encourage cousin marriage, as it is, say it with me know, a cultural thing. It is only logical to infer that cousin marriage is going to happen more often within families for whom it is normal and encouraged.

As far as I know, there are not yet any comprehsive statistics on multi-generational cousin marriages, but the WHO was in the process of gathering data in the early '00s, so hopefully numbers will be forthcoming.

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Its worth pointing out that until a society reaches a post-industrial state of development (and this has only happened in that last century or so, and certanly not everywhere), it really doesn’t matter if your children die of a crunched gene or some other malady, since you’d expect to lose half of them, anyway.

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Moderator’s Note: Moving from Great Debates to Comments on Cecil’s Columns.

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Note that the BBC article does point to long-term multigenerational cousin marriage.

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I do have two first cousins that got married and had three normal children. Their mothers are identical twins, meaning genetically they are half-siblings.

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When I did genealogical research I was surprised to see how many of the people I went to school with (including a couple that I had major crushes on [or at least lust for]) were also my cousins, all of them descended from ancestors who had died within the past century and yet we had no idea we were related. Most of my 19th century ancestors, like most of rural America in the 19th century, tended to have large families (fewer than 6 kids was rare, more than 15 was not unheard of) and thus by the late 20th century they often had hundreds or even thousands of descendants scattered through the nation. (I know through exchanged emails related to genealogy threads that at least a couple of Dopers, neither of whom I’ve met and neither of whom have ever lived in the same state or even the same region of the country and neither of whom have a surname I had ever heard before, are descendants of ancestors recent enough that I have photographs of one and knew the last surviving child of the other.*)
There’s a student where I work who I know by her name (I’ll call her Eusebia Lampton because that’s not her name) is a descendant of an old man I knew who I’ll call Eusebius Lampton, who was my grandfather’s biracial first cousin. She’s a dark skinned black woman and I’m a fair skinned blonde man and while I’ve never brought it up for obvious reasons she and I share a set of ancestors (my great-great-grandparents) who lived well into the 20th century in spite of common sense would say is “no relation”.

When you look at how many millions of Americans (white, black, and other) have Irish/English/Scots-Irish ancestry and consider that in the 17th and 18th centuries these breeding pools weren’t that huge, anybody whose family has been here for more than a couple of hundred years probably has millions of cousins in this nation alone. In a nation like England, where there are tens of millions of people living in a nation smaller than many of the American states and whose ancestors have lived there for hundreds if not thousands of years it’s probable that almost every marriage is between people who are related many different ways.

The point being: I almost wonder if by this time, when you could easily marry a person who’s your 3rd, 4th, 5th, 6th, 7th, and (by 19 different ways) your 9th cousin and never know it, if it’s that much more dangerous marrying a ‘stranger’ than a 2nd or 3rd cousin. (1st is more “icky” than dangerous- and whose side would the grandparents sit on at the wedding?)
*If you have any of the following surnames in your direct line and ancestry from the mid-Atlantic region and would like genealogical info, drop me a line and I’ll be glad to share what I have as we’re probably related: Caton [several spellings], Bibby [several spellings inc. Bibbie/Bybee/Bebby and others], Darby, Deramus, Geiss (also spelled Guice and Guyce), Gissendanner, Golson (also spelled Golsan and Gholston), Lee, Milner, Rawlinson (several spellings), Roy, Stoudenmire, Tanner, Tinsley, Trawick [several spellings], Tschudy (also spelled Judy, Choody, von Tschudi, and other ways)- there are lots of other surnames as well of course but they’re a lot more common (Boggs, Cotton, Moore, Smith, Thompson) or a lot further back and thus less likely to have a match.

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Few if any genealogies are better documented in the western world than that of the British Royal family (they have their own official genealogist in fact) and of course their ancestors have more often than not married cousins for centuries and centuries. At least a few of these were first-cousin marriages (most recently Albert and Victoria) and many more were cousins through several different ancestral lines. Princess Di and Charles were distant relatives and, IIRC, even the commoners Fergie and Elizabeth Bowes-Lyon shared known (though distant) ancestors with their spouses.

I know about the spread of hemophilia and, slightly earlier, porphyria, but in general is the health of the royal family less than that of society at large? (That’s not rhetorical, I’m actually asking.) Their life expectancies seem to be about the same- no more or less than average overall- the queen’s father died fairly young but her uncle lived to be old and the queen herself is in her early 80s and seems to be doing well. (Longest lived of the immediate family was admittedly the Queen Mother, a non-royal by birth who was only very distantly related to her husband and may have given a nice boost to her daughter and grandkids/great-grandkids.)

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I hope you hill Billies don’t get offended that Science doesn’t agree with you. Animal Scientists have proven over and over again that inbreeding while it strenghtens gene frequencey of traits you want, it also does so for undesireble genes also. There is a term for the extra vigor of outcrossing (marrying way outside the family) which is called Hybrid Vigor. You need to study up folks, Get away from the sisters bedroom.

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Tras, to quote the Perfect Master. Little things cause little problems. Big things cause big problems. The inborn tendency away from incest means that things will never get as bad as with dog breeds in the case where everyone is culturally free to choose their mates.

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I don’t know about overall health of the royal family, but it seems to me that questions of that type would have been the ones that the Royal PR flacks would get uncomfortable with.

…

I had a thing typed up about the House of Habsburg, which liked to use uncle/niece matches to keep power, specifically Joanna the Mad and her great ^ 3 grandson Charles II of Spain (who was descended from her about 21 different ways :eek: ), but upon reflection, totally different royal line.

That said, how does the genealogy of the Spanish royalty compare to the British royals in your opinion if you have one?