The royal wedding and outbreeding

By Razib Khan | April 29, 2011 2:14 pm

In the wake of the post from earlier this week on the inbreeding within the House of Windsor (and current lack thereof), Luke Jostins, a subject of the British monarch, has a nice informative post up, Inbreeding, Genetic Disease and the Royal Wedding. This tidbit is of particular interest:

In fact, eleventh cousins is a pretty low degree of relatedness, by the standard of these things. A study of inbreeding in European populations found that couples from the UK are, on average, as genetically related as 6th cousins (the study looked at inbreeding in Scots, and in children of one Orkadian and one non-Orkadian. No English people, but I would be very suprised if we differed significantly). 6th cousins share about 0.006% of their DNA, and thus have about a 0.06% chance of developing a genetic disease via a common ancestor. Giving that the Royal Family are better than most at genealogy, we can probably conclude that the royal couple are less closely related than the average UK couple, and thus their children are less likely than most to suffer from a genetic disease. Good news for them, bad news for geneticists, perhaps?

That’s an interesting flip side of aristocratic consanginuity, aristocratic cosmopolitanism. For example, Victoria of Sweden, the heir to the throne, has a Brazilian maternal grandmother and German maternal grandfather. Her father is by and large of the Northern European aristocracy,* but because he is of the House of Bernadotte his paternal lineage is rooted in a region on the alpine fringe of southwest France. The European aristocracy then serves as an interesting window into how cultural context can shape genetic variation.

Also, a sidelight of curiosity is that Duchess of Cambridge (formerly Kate Middleton) has a maternal grandmother who comes from a lineage of laborers and miners. That’s certainly a commentary on the possibilities for social mobility. There is a strong likelihood that a 20th century working class laborer will be the great-great grandparent of the British monarch at some point in the 21st century.

CATEGORIZED UNDER: Culture, Genetics

Comments (27)

  1. leviticus

    The stereotype of inbreeding usually involves 1st cousins, whereas the reality in many areas, unless otherwise dictated by cultural demands, is marriage between two individuals who are related in multiple ways but not extremely close. I’m from the Southern Appalachian region, notorious for its 1st cousin marriage stereotype, and in my area, currently, the scenario I gave is more accurate. My parents, for example, are descended from several different ancestors who were born roughly 1750-1850, but no later. The kinship was distant enough that it was forgotten by my grandparents’ time, despite oral history in my family going back to that era. My siblings likewise married individuals with whom we share ancestors, but no memory of kinship, mostly from that generation that came of age around the War of 1812. There were 1st and 3rd cousin marriages, but that is a thing of the past, even 5th cousin marriage is commented on these days. Continued marriage with individuals with whom you share distant ancestors remains common, however. Totally unawares to me, most of my highschool girlfriends and I shared ancestors who flourished 6-7 generations ago. Complicating this is illegitimacy, which obscures sometimes close kinship. I almost dated the granddaughter of one of my great-grandad’s illegitimate daughters until warned not to.

  2. Robert

    “6th cousins share about 0.006% of their DNA, and thus have about a 0.06% chance of developing a genetic disease via a common ancestor.”

    That somehow doesn’t sound quite right to me. If two people share .006% of their DNA wouldn’t their chance of developing a genetic disease be some power of 2 multiple of the .006 probability like 8 or 16 rather than a ten-fold one?

  3. Semolina

    Surely Bernadotte was of Scandinavian descent, since the elite of France were quite Norman in stock?

    The Normans seemed to slot themselves into royal positions, even as far south as Sicily, but they seemed to never impose their culture. If they had a culture. The same is true with the Vikings… from Ireland to Russia and many points in-between.

    Even Phil the Greek considers himself ‘Scandinavian’:

  4. semolina, that kind of sounds retarded. are you stupid, or do you play a stupid person on the internet? 🙂 to be non-retarded, even if bernadotte was of the local southwest french nobility, that element was in the medieval period assumed to even pre-date the franks, insofar as it preserved a gallo-roman tinge down the carlognian period (though they did adopt some frankish cultural forms such as trousers rather early one).

  5. “That’s an interesting flip side of aristocratic consanginuity, aristocratic cosmopolitanism.”

    It is possible that the cosmopolitanism in addition to the consanginuity may be a factor in aristocratic genetic disease.

    Inbreeding increases the likelihood of having a genetic disease from a recessive gene that is in the gene pool.

    But, if you have a community that is highly inbred for many generations, you get the same kind of phenomena in the population that you get in organism that alternate between being “selfers” and engaging in normal sexual reproduction. You get a dumping of the load of deleterious mutations in the early generations, which removes a lot of the potentially harmful recessive genes from the population or at least greatly reduces their frequency, followed by many generations in which there aren’t any fatally flawed (from a reproductive fitness sense) recessive genes in the population at a high frequency.

    But, if a harmful recessive gene is then reintroduced into a fairly consanguinity prone gene pool as a result of cosmopolitan marriage patterns, this doesn’t happen. You have an aristocratic gene pool has the downsides of being inbread, without the arguably beneficial mutation load dumping that takes place when an inbred population stays inbred for many generations. So, in a generation or two after the new harmful recessive gene is introduced into the artistocratic gene pool due to cosmopolitian marriage patterns, the victim of the mutation dumping that inevitably follows, when harmful recessive genes appear in duplicate in an individual in an inbred population, is an artistocrat or perhaps even a royal.

  6. oh hey, if any of you don’t know why semolina’s comment is moronic in so many ways that can’t even be deconstructed without a lot of time because of the multiple layers of idiocracy, don’t comment. 🙂 it requires an understanding of the ethnogenesis of the frankish, and later norman nobility, and, also an awareness of the rather shallow roots of most european ennobled and gentry lineages. being stupid along so many chains of causation is a feat, but an offensive one.

    for example, an estimation of william the conqueror’s pedigree shows that he mostly non-scandinavian, with a lot of frankish and breton. i estimate 5/32 “quick and dirty.”

  7. #5, interesting model. theoretically possible. i’d just say i’m empirically skeptical of load-purging models in humans, though i’ve seen some references to the phenomenon in the literature.

  8. robert, perhaps taking into account basal relatedness?

  9. Denic, et al., had an interesting paper in 2010 that also argued that inbreeding could have evolutionary value in certain circumstance: “Inbreeding increases the speed of selection of beneficial recessive and co-dominant alleles, e.g. those that protect against diseases. In populations endemic with malaria, the prevalence of consanguineous marriages and the frequency of alleles protective against malaria are both very high.”

    The willingness of the author to consider both sides of the coin may be a product of his UAE academic affiliation, as UAE is one of the most inbred (and also inbred aristrocracy dominated) populations in the world.

    The issue is quite amenable to study with Monte Carlo models (that should be highly accurate since we understand the mechanism involved so well). It is certainly possible that mutation rates are sufficiently high that only extreme inbreeding for very long time periods are sufficient to produce mutation load dumping that can keep up with it, but it ought to be possible to get pretty accurate estimates of the relevant constants in that model from empircal evidence, and to use that to determine what the critical thresholds are in a quantitative way.

  10. JonHarper

    The Rothschild’s married their cousins quite often in the 1800’s with no apparent problems.

  11. Tobermory

    Do Victoria’s Brazilian ancestors mean she is of part-African descent (like Sweden’s Prime Minister).

    Incidentally, the wedding between William Battenberg and Katie Goldsmith us a wonderful moment of German-Jewish reconciliation.

  12. Do Victoria’s Brazilian ancestors mean she is of part-African descent (like Sweden’s Prime Minister).

    if her family were recent immigrants to brazil maybe not. but i don’t know that genealogy.

  13. Incidentally, the wedding between William Battenberg and Katie Goldsmith us a wonderful moment of German-Jewish reconciliation

    lol. not all people with “jewish names” are jewish.

  14. Robert

    Razib, upon closer reading of Luke Jostin’s article it appears that the average person retains about 10 recessive diseases so yes the 25% odds any children inheriting the defect is proportional to probability of any of those two sets of base pairs matching up. Since Luke Jostins is a postgraduate student working on the genetic basis of complex auto-immune diseases I’ll take his word for it that that comes out to .06% since this number also jibes with the observed number of genetic defects found in the general population. (Something I should have taken the time to look up prior to originally posting!)

  15. Since Luke Jostins is a postgraduate student working on the genetic basis of complex auto-immune diseases I’ll take his word for it

    well, if you see something off by exactly an order of magnitude, there’s often reason to wonder if there was a simple multiplication error. mathematically fluent folk are often bad at simple arithmetic 🙂

  16. I thought you were gonna stop saying retarded?

  17. true. thanks for catching me. but isn’t stupid X stupid X stupid = retarded? 🙂

  18. I don’t care (you know me), I just felt like being a pest. I didn’t know there was a stupid cubed law re: retardedness.

  19. i assumed u were being hegemonic for fun!

  20. Dragon Horse

    Taking off ohwilleke ‘s point…Dienekes once said:

    “Populations that have practiced inbreeding for a long time have abolished many of their harmful alleles, because such alleles are expressed more often, the individuals which express them die or fail to reproduce, and the alleles are removed from the gene pool. On the other hand, by chance, it is possible that alleles with small harmful effects may in fact be fixed in the population, and this reduces the quality of the population.”

    That is something we don’t think about much…

    That being said, I would rather be the person who carriers a deleterious mutation than die from an expressed trait.

    I’m only 68% homogenous, according to my 23&me data, my fiancee is Swiss, and 69% (which is amazing based on my stereotypical of Switzerland and the fact she is European). If you think that sounds interesting, my father is 67%. :-O

  21. Robert

    “I’m only 68% homogenous”

    Don’t you mean homozygous?

  22. Dragon Horse

    LOL yes, Homozygous. Not homogenous or homosexual. 🙂

  23. Roger Bigod

    Fussiness about consanguinity seems narrow-minded, given the example of the Randolphs of VA. They had at least a dozen cousin marriages over 3 or 4 generations. There was a saying “Only a Randolph is good enough for a Randolph.” There’s an example of a marriage between two individuals who were themselves products of a Randolph cousin marriage. One of the children of the marriage had congenital deaf-mutism. But his parents were cousins as members of the Bolling family and there was a case of deaf-mutism in the child of another consanguinous marriage in that family. The eccentric politician John Randolph of Roanoke was hypoandrogenic, with a high pitched voice, slender build and no need to shave. But hypogonadism can be acquired and there are no other cases in the family. Except for that questionable case, the Randolphs get a clean bill of health.

    In perspective, the Randolphs were prolific, with many surviving children in the first 3 or 4 generations, so the number of inbred people was a small fraction of the surviving descendants in 1800. Their dynastic fortunes declined after that because growing tobacco for export became a losing business, not because they produced an army of imbeciles.

    The take-home lesson is perhaps that our attitudes about consanguinity are culturally determined and somewhat irrational.

  24. Nice post Razib. You and readers might find interest in a short piece I wrote for National Geographic, piggybacked to the Tut DNA story, about arguments FOR royal incest. It’s at


    “If the royals knew of these potential downsides, they chose to ignore them. According to Stanford University classics professor Walter Scheidel, one reason is that “incest sets them apart.” Royal incest occurs mainly in societies where rulers have tremendous power and no peers, except the gods. Since gods marry each other, so should royals.”

    For starters.

  25. Huxley

    I think if you trace it back, Prince William’s surname ought to be Oldenburg from north Germany. Battenberg/Mountbatten was not Philip’s paternal lineage.

  26. Robert

    Greg Clark via TGGP:
    “”The modern meritocracy is no better at achieving social mobility than the medieval oligarchy. Instead, that rate seems to be a constant of social physics, beyond the control of social engineering.”

    One of The Bell Curve’s major points was that assortative mating in modern meritocracies would indeed lead to less social mobility as society slowly bred itself into castes.


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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


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