Pure Jewish blood?

By Razib Khan | November 1, 2007 2:56 pm

William Saletan has a piece up over at Slate, Jewgenics, which covers his reactions to a talk (you can view it online) sponsored by AEI around Jon Entine’s book Abraham’s Children: Race, Identity, and the DNA of the Chosen People. I’ve read the book, though I don’t have time to listen to the talk right now. But I wanted to offer a quick perspective on one point in Saletan’s piece:

According to Entine, the rate of Jewish “outbreeding”–procreating with non-Jews–is half a percent. That’s the lowest rate of any population in the world today….


First, I don’t know if that is the lowest rate of any population in the world today. There’s a lot of populations out there. Additionally, the 0.5% is per generation over the last 2,000 years. Since American Jews outmarry at rates of 25-50%, and they are a substantial proportion of the world’s Jewry, the 0.5% number doesn’t make any contemporary sense. Rather, Jon is reporting data which specifically looks at the proportion of non-Jewish lineages that seem to have slipped into the Jewish gene pool over the past 2,000 years.
But, that doesn’t mean that in every generation only 0.5% of Jews married out, it means that 0.5% of non-Jews married in! There is plenty of historical data for Jews leaving Judaism through outmarriage, from Spain before the expulsion of 1492 to 19th and early 20th century Germany. The rates are well above 0.5%, but, these Jews interjected Jewish lineages into the gentile population. In contrast, it seems that far fewer gentiles married into the Jewish people over the past few thousand years. The reasons for this are two-fold: 1) Judaism makes it hard to convert and 2) Islam and Christianity have often imposed capital penalties upon those who convert to Judaism from their religions. The exceptions often prove the rule, there are instances where Christian converts to Judaism fled to Muslim Spain, as there the authorities would tolerate converts from Christianity to a non-Christian religion. I suspect that Jewish objections to converts is in part a cultural adaptation due to the long incubation of Jewish culture within Christendom and the Dar-al-Islam, when perceptions that Jews were poaching members of the dominant religion could result in communal retribution.
Looking at the 0.5% per generation number it is also interesting to consider what that means genetically. Assuming discrete generations of 25 years and iterating the 0.5% gene flow number, one projects that over 2,500 years originally non-Jewish genes would form about 39% of the Jewish gene pool today. That would be a substantial amount in terms of ancestry, and certainly enough so that selection could operate and reshape Jewish phenotypes due to the introduction of non-Jewish polymorphisms. In other words, some of the characteristic diseases or Jews might very well have a non-Jewish origin and risen in frequency due to in situ evolutionary dynamics within the Jewish population.
Via Ruchira Paul.

CATEGORIZED UNDER: Genetics
  • Scott Conger

    It might be true that “only 0.5% of Jews married out” (although I doubt any accurate statistics exist) but marriage is hardly the only source of genetic exchange. What about prostitutes, rape, adoption, mistresses, etc?
    I have trouble believing the idea that two human populations can live right next to each other and not interbreed at a decent rate.

  • http://www.scienceblogs.com/gnxp razib

    It might be true that “only 0.5% of Jews married out” (although I doubt any accurate statistics exist) but marriage is hardly the only source of genetic exchange. What about prostitutes, rape, adoption, mistresses, etc?
    the numbers are derived from analyses of uniparental lineages from what i recall. in other words, they’re pretty clear. the social phenomena you refer to are irrelevant, since the comparison between jewish and non-jewish lineages isn’t inferred from historical data, it is derived from the coalescent patterns in the molecular clocks.

  • gcochran

    No, from analysis of autosomal genes.

  • Alec

    very good clarification on how the 0.5% number is about non-Jews marrying in and not about Jews marrying out of the group.
    On the other hand, I find it odd that Saletan (and Entine also to a large extent) makes much about “Jewish intelligence, Jewish genes, and Jewish values” but then kick Sephardic Jews to the curb even though Sephardic Jews are a not unsubstantial 20% of the total Jewish population.
    Practically all of the references to IQ scores or disease frequency, and the speculations as to the evolutionary forces that may have affected these things, are all in reference to Ashkenazi Jews. This does not necessarily invalidate Entine’s arguments, but certainly makes things less than a slam dunk. Sephardic Jews and Ashkenazi Jews historically similar values and histories, respect for literacy, etc., but I don’t see much of an attempt by either writer to explain why Sephardic Jews apparently don’t perform as well on IQ tests.

  • http://www.accidentalblogger.typepad.com Ruchira

    Sephardic Jews and Ashkenazi Jews historically similar values and histories, respect for literacy, etc., but I don’t see much of an attempt by either writer to explain why Sephardic Jews apparently don’t perform as well on IQ tests.
    Doesn’t Charles Murray refute that? Not on the point of Tay-Sachs but on intelligence? Maimonides, Spinoza, Justice Cardozo, Jacques Derrida, Benjamin Disraeli, Primo Levi …. to name just a few? That would point to culture, not genetics. My co-blogger Anna Levine has weighed in on this.

  • http://www.scienceblogs.com/gnxp razib

    Sephardic Jews and Ashkenazi Jews historically similar values and histories, respect for literacy, etc., but I don’t see much of an attempt by either writer to explain why Sephardic Jews apparently don’t perform as well on IQ tests.
    cochran and harpending don’t think that ashkenazi jews were selected in the same way as sephardic ones. primarily they note that the occupational profiles differed quite a bit, and more non-ashkenazi jews were employed traditionally blue-collar/artisan work. cochran and harpending tend to disagree with murray that jewish intellectualism dates back to a very early period, at least in a broad sense. i tend to agree with them. i don’t think the bible is any more genius than the gathas or the vedas or even the kalevala! and as cochran has noted the exceptional innovative intellectuals during antique period were greeks, not jews.

  • diana

    Ruchira,
    To a degree this subject has become bogged down & fogged over by discussion of IQ tests. Let’s say for the sake of argument and to concede a point that IQ tests predict nothing. Let’s throw the whole subject out the window. You are still left with the uncomfortable (for some) fact that Ashkenazi Jews have contributed a quite staggering proportion of numbers of mathematicians and physicists (not to mention mathematical economists), and further, a large proportion of top-rank creative theoreticians have been Ashkenazi Jewish.
    Of course the Sephardic Jews have produced a creative elite. But any group of people does, especially folks who think of themselves quite consciously as an elite, as the Sephardim do. It’s when dozens of brilliant scientists are produced by the average working class that you have to wonder what’s going on. I don’t doubt that culture has *something* to do with it…British Jews and Australian Jews seem rather less flamboyant about achievement than have Russian, German and American Jews, and they are the same Ashkenazi stock. But you can’t rule out genes. So far, IMO, Harpending/Cochran have produced the most satisfying explanation of this: and the beauty of it is that it’s got nothing to do with Judaism. I like this because it’s the opposite of anti-Semitism – because it has nothing to do with Judaism. All we are talking about here is selection pressures. You could have gotten the same result out of any group of people. Either they died or adapted.
    By the way, an historian named Seth Schwartz argues that Jews were quite “un-Jewish”, mostly illiterate, until well into the 6th century. I haven’t read his book yet so I can only speak about what I’ve seen on the ‘net, though.
    http://press.princeton.edu/titles/7179.html This argues against the Charles Murray thesis.

  • Caledonian

    I like this because it’s the opposite of anti-Semitism – because it has nothing to do with Judaism. All we are talking about here is selection pressures. You could have gotten the same result out of any group of people. Either they died or adapted.

    This is heady and dangerous territory – not because of antisemiticism or its opposite, but as you note, because it has nothing to do with either of those things.
    If we could have gotten the same result with any group of people, perhaps we can in the present. It would be useful to determine what tradeoffs were incurred in the process – what, if anything, are Ashkenazis especially poor at on a statistical/group level?

  • http://www.scienceblogs.com/gnxp razib

    By the way, an historian named Seth Schwartz argues that Jews were quite “un-Jewish”, mostly illiterate, until well into the 6th century.
    well, they were mostly farmers up until this period. like everyone else. the ‘change’ where jews went from being occupationally reflective of the majority toward an urban minority which did not engage in agriculture came with the transition between late antiquity to the early medieval era and the rise of islam & christianity.
    - what, if anything, are Ashkenazis especially poor at on a statistical/group level?
    they’re visuo-spatial IQs are below average. i believe 1/3 a standard deviation below the gentile white mean. while medicine, law and natural sciences & mathematics are saturated with ashkenazi jews, this seems far less noticeable in engineering. the imbalance on websites which catalog prominent 20th century jews is pretty noticeable. of course, there was discrimination, but there was discrimination in the other fields too.

  • Caledonian

    So if there was massive selection for linguistic ability, at the expense of visuospatial skill, there might also be deficiencies in mental skills relying upon and/or statistically associated with visuospatial skill. I’ll have to look into that.
    What would the social consequences have been for a medieval Jewish boy who couldn’t pull off his Bar Mitzvah because he was dyslexic? (Well, not just that one ceremony, of course.)

  • Suraj

    The ‘Brahmin’ caste of South India, especially of Tamil Nadu, Kerala and other neighboring states are similar to the Ashkenazi Jews as far as their historical and contemporary contributions to the fields of science, maths, literature, music and governance in India is concerned. (in fact, all the internationally acclaimed Indian men of science and mathematics belong to this particular sect.)
    There seem to be a lot of similarities between the Ashkenazi Jews and the Tamil Brahmins – especially in the aspects of inbreeding, pressures to excel in mathematics, philosophy and music, rigorous and early training in vedic scriptures, abstract concepts in vedantic philosophy, sanskrit etc.
    This phenomenon doesn’t seem to have been studied in detail yet, let alone the Ashkenazi connection.

  • http://www.accidentalblogger.typepad.com Ruchira

    (in fact, all the internationally acclaimed Indian men of science and mathematics belong to this particular sect.)

    Suraj:
    Dr. Hargobind Khurana (Nobel Prize in Physiology and Medicine, 1968) is a Punjabi.

  • endo

    (in fact, all the internationally acclaimed Indian men of science and mathematics belong to this particular sect.)
    Birthplaces of important Indian mathematicians…
    http://www-groups.dcs.st-and.ac.uk/~history/BirthplaceMaps/Places/India.html
    There is a cluster in South India , but also a significant numbers from North-West India.

  • http://www.scienceblogs.com/gnxp razib

    The ‘Brahmin’ caste of South India, especially of Tamil Nadu, Kerala and other neighboring states are similar to the Ashkenazi Jews as far as their historical and contemporary contributions to the fields of science, maths, literature, music and governance in India is concerned. (in fact, all the internationally acclaimed Indian men of science and mathematics belong to this particular sect.)
    1) actually, they aren’t similar. the ashkenazis have contributed 20% of nobel prize winners. the brahmins of tamil nadu are notable for their outsized contribution for south asians, but the analogy only works if you compare it to the differing comparative poupolations and their respective contributions to modern science (gentile whites and south asians).
    (raman, chandrasekar and ramanujan aren’t anything to sniff at, but the comparable ashkenazi jewish list is endless).
    2) taking into account the relatively small number of indian men of science in the modern era compared to the number of brown people, do note that khurana was a khatri punjabi, bose, mahalanobis and amartya sen are all bengalis. so though tamil brahmins have been prominent, to say that “all the internationally acclaimed Indian men of science and mathematics belong to this particular sect” stinks of either stupidity or ignorance (i suspect the latter, the stupid wouldn’t deign to generalize).

  • Spike Gomes

    razib:
    Have there been many tests done on IQ in certain castes in India? I would think the amount of high caste Indians winning science prizes in the future should rise just due to the spread and availability of a decent university education in India and the ability to study abroad.

  • diana

    If you widen “Indian” to subcontinental, there’s Abdus Salam, a Pakistani. (I guess, Punjabi?) He considered himself a devout Muslim but was an Ahmadi.
    Also, about those great Brahmins, one would expect, after 100 generations (?) of inbreeding a priesthood whose purpose was to commit abstruse religious tracts to memory they would have produced some superior men of science. What Cochran/Harpending explains is how (for example), a Feynman, a Gell-Mann, a Schwinger is produced from the same small group of people, whose parents were, on the surface, not prestige high-wage earners, or members of a favored caste.
    Not to mention Emmy Noether, Lise Meitner, Karl Schildkraut, and a score of names that never seem to make it the Top Ten List, but whose contributions to 20th century physics were seminal.

  • Roger

    Razib, I think the ‘low’ visio-spatial score of Ashkenazi jews is great evidence of the uselessness of the test. It is quite a bold statement to say that A.Jews have historically performed poorly relative to East Asians, who supposedly have the highest such score, in technical fields such as physics, mathematics, engineering(I would say abilities in Physics and Mathematics are quite related to Visio-Spatial ability). People like Richard Feynman were clearly amazing engineers as well as scientists. I’m currently an Phd student at an ‘elite’ engineering department, and I can guarantee that Jews are certainly not underrepresented in either the faculty or graduate student body. Im South Asian btw.
    It is true that Tamil Brahmins have historically outperformed other Indian groups, but there are other such groups in India as well: Parsees, Jains, Bengali Brahmins. In addition individuals of numerous other South Asian communities, such as Khorana and Salam, have also excelled, so it is unfair to place the Tamil Brahmins on their own pedestal.

  • Roger

    Oh btw, how do you explain Israel’s high tech defense industry with all those low visio-spatial Iqs?

  • http://www.scienceblogs.com/gnxp razib

    jews do well in physics and mathematics, that isn’t news to me. what proportion of the engineering dept. is jewish? the key isn’t whether jews are underrepresented, it is whether they are not as well represented normalized to equivalent fields.

  • diana

    “engineering dept. is jewish? the key isn’t whether jews are underrepresented, it is whether they are not as well represented normalized to equivalent fields.”
    Razib I don’t see that at all. I think Roger has pointed out a flaw in the testing, which is one reason I do not like to argue the point about heritability with respect to test scores alone. The real aptitude test is life scores and lots of factors go into that mix.
    Confession: I don’t have stats, but let’s say that A-Jews, 2% of the general population, represent 6–8% of the members of the IEEE. That may not sound overwhelming next to the 25% of elite physicists and mathematicians (or is it 40%? whatever…) but it still indicates that the testing is a bit whack. Punching 3X to 4X above your weight is still noteworthy. When you do badly on visuo-spatial scores…?? Clearly, something else is involved here. Other brain functions are taking over – and there’s custom and discrimination.
    I know that the GNXP crowd curls a lip at the idea that human exclusivity trumps genes, but it can, and does. It’s easy for us to laff at anti-Semitism now (at least, some of us are amused by it), but until the 1950s, engineering was hard-core WASP and very exclusive. I have an uncle who was an electrical engineer. It was brutally tough for him. He was about 6’2″, with blue eyes and sandy hair, loved guns and pro football, in short, was not your typical Brooklyn Jew (which may explain why he ended up an electrical engineer?).
    Engineering is a real team-tag sport, and if you didn’t fit the profile, you did not get promoted. Jews are very into upward mobility, and a lot of other guys of his generation probably said, “why bother?” There are other occupations open to a guy who has the ability to be an engineer, but not the obsession/aggression.
    Now that anti-Semitism is all but vanished in terms of occupational choice, a Jewish guy with the brains to be an engineer is more likely to go into law or finance. The Feynmans, of course, go onto being Feynmans.
    Phun Phact: Hans Albert Einstein (half-Jewish, half-Serbian) was one of the top hydraulic engineers of his time:
    http://www.lib.berkeley.edu/WRCA/einstein.html
    According to one of the myriad Einstein bios, when son told father he wanted to be an engineer, dad huffed, “That’s a disgusting idea!” He later became quite proud of his son.

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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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