Risch’s Conjecture

As some of you already know, Henry and I have put forth the hypothesis that the observed high intellectual achievement of Ashkenazi Jews is a result of natural selection for intelligence over the Middle Ages. We think there’s a pretty good case. One important supporting fact is that high Ashkenazi intelligence shows up everywhere they live. You see it in Russia, the US, Latin America, Israel, etc. It doesn’t spring from a single cultural milieu: you saw it in Jewish kids raised in turn-of-the-century Vienna, in Israeli kibbutzes, in Bronx tenements, and in Stalinist Russia. It’s not a consequence of Talmudic study – you see the same results in religious and irreligious people of Ashkenazi descent.

Interestingly, other ethnic groups show a similar pattern. Those that exhibit high levels of intellectual achievement in one country do so in others. Chinese do well in every society, even if they arrived as illiterate tin miners, as they did in Malaysia. Swedes in the h0meland score like their cousins in Minneapolis. Sub-saharan Africans do poorly in every country they inhabit. This suggests that genetic factors may be the main general cause of observed intergroup differences in intelligence and academic achievement. The selective pressures that caused these differences may not be as easy to figure out as in the Ashkenazi case, particularly if they acted over tens of thousands of years.

As Neil Risch forcefully put it, in an interview with Karen Kaplan on our paper about Ashkenazi Jews, “What are their theories about those on the opposite end of the spectrum? Do they have genetic theories about why Latinos and African Americans perform worse academically?” A truly perspicacious question – to ask it is to answer it..

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81 Responses to Risch’s Conjecture

  1. Ron Pavellas says:

    To what do you attribute high scores in IQ tests and in academia by persons who are not Ashkenazy and not Chinese? Have there been studies of genetic characteristics of Mensa members, for instance?

    • hurrhurrdurr3 says:

      Intelligence as measured by IQ is a quantitative trait which is normally distributed within populations.


      So people of every race can be theoretically be found at every level of the IQ distribution. It’s just a question of probability.

      1 in 407 African-americans (mean=85) has an IQ of >130 (commonly used threshold for giftedness)
      1 in 33 Whites (mean=100) has an IQ of >130
      1 in 15 Asians (mean=106) has an IQ of >130

  2. Porter says:

    Do you have a refutation of claims that the Burakumin group in Japan has IQ well behind the general population of Japan (as well as anti-Burakumin stereotypes and discrimination), but not among Japanese-American populations? I believe this was presented by Ogbu in the 1970s and it occasionally gets cited, but I’ve never heard a hereditarian response to it (which is pretty unusual, this is one of only a handful of claimed anomalies where I haven’t heard any persuasive responses).

    • JL says:

      There are apparently one or two decades-old studies of Burakumin IQ. There are no newer studies or studies of whether the gap reflects a test bias or a genuine deficiency. The 1995 NY Times article suggests that as overt discrimination has abated, the Burakumin have quickly converged towards the ethnic Japanese — perhaps there is no longer a gap in 2011 among younger cohorts? There’s simply too little information to say much about the Burakumin-Japanese gap, let alone to suggest that it’s analogous to the black-white gap in America.

    • Jason Malloy says:

      I often see media assertions like Steve Olson in The Atlantic: “Yet when the Buraku emigrate to the United States, the IQ gap between them and other Japanese vanishes.” This claim is somewhat apocryphal. There is no data for Burakumin in the US. False claims about US IQ data have mutated second-hand from John Ogbu who claimed a study showed that the Baraku immigrants here “do slightly better in school than the other Japanese immigrants”. The book chapter Ogbu references for this claim (Ito 1966) however, is by a pseudonymous author who relied strictly on gossip from non-outcast Japanese communities in California to surmise how the outcasts here might be performing. The author’s informants believed the US outcasts were more attractive, more fair-skinned, and made more money. Though– as a testament to Ogbu’s immaculate scholarship– the author reported no gossip about how these Burakumin performed in school.

      * Ito, H. (1966) Japan’s outcastes in the United States. In G.A. deVos and H. Wagatsuma (eds.), Japan’s Invisible Race. Berkeley: University of California Press.

      • Jason Malloy says:

        Here’s one from a textbook. It’s pretty appalling stuff… yet typical:

        “But when Burakumin families immigrate to the United States, they are treated like any other Japanese. The children do just as well in school–and on IQ tests– as any other Japanese-Americans. (Ogbu 1986)”

        So not only does Ogbu make claims that go beyond his source, the scientists and journalists that cite Ogbu follow his lead and make up even more amazing lies about what Ogbu said. It’s all for the greater good!

      • Porter says:

        Thanks Jason, you have fully sated my curiosity.

  3. Porter says:

    Also, the differences seem to have declined:


    “A 35-year-old study in Japan found that buraku children had lower I.Q.’s than non-buraku children in the same public schools. Scholars who examined the data say the differences reflect general apathy and lack of self-esteem, a result of discrimination and contempt from society as a whole.

    In the field of education, burakumin have made stunning progress. But they also remain stunningly far behind.

    Truancy rates in elementary school in 1960 were 12 times as high for buraku children as for others. Now they are twice as high.

    Burakumin have almost caught up with their peers in the proportion who graduate from high school, a tremendous achievement. But only about 24 percent of burakumin go to college, compared with 40 percent of other Japanese.”

  4. billswift says:

    I don’t understand your point, Porter. If you are trying to claim that because Burakumin are socially, rather than genetically, disadvantaged, that proves other groups are only socially disadvantaged, then that is fallacious. If you are trying to make some other point, I can’t see it.

  5. Leonard says:

    “What are their theories about those on the opposite end of the spectrum?” asked Neil Risch, director of the Institute for Human Genetics at UC San Francisco, who finds the matter so offensive he can barely discuss it without raising his voice. “Do they have genetic theories about why Latinos and African Americans perform worse academically?”

    Of course they don’t. As we all know, genes can cause people to be above average, but never below average. Subaverage performance is always caused by “society”. African Americans (especially those living in Africa) obviously are specially challenged on mental tests, because of slavery and the legacy of colonialism.

    • Jon says:

      Especially those in Ethiopia even though it was always an independent country and knew a lot less endogenous slavery than most of the rest of Africa. It is also pure coincidence that Ethiopia was, by African standards, relatively well when ruled by Amhara elite (an ethnic group with significant Caucasoid component) and fell into chaos and poverty when their more sub-Saharan Oromo brothers took over.

  6. I had corresponded with Prof. Harpending in the last year about a simple experiment: the Ashkenazi intelligence hypothesis rests on heterozygote advantage. Has anybody ever just gotten carriers of the various lysosomal storage disease genes to take intelligence tests? Wouldn’t that give a pretty clear answer?

  7. Greying Wanderer says:

    I’d imagine if a population had an average IQ of 85 the goldsmith and silversmith segment of that population might have an average of 100.

    I’d also imagine if a population had an average IQ of 100 the goldsmith and silversmith segment of that population might have an average of 115.

    If a mercantile group made a project out of marrying into the goldsmith and silversmith segment of the population they lived among then their average IQ might be effected by the process.

  8. “This suggests that genetic factors may be the main general cause of observed intergroup differences in intelligence and academic achievement. ”

    No kidding?

  9. Greybeard,

    “I’d imagine if a population had an average IQ of 85 the goldsmith and silversmith segment of that population might have an average of 100.”

    Seems like Hindu caste would be the perfect avenue to explore that sort of variance. You probably know of something if such exists.

    • Greying Wanderer says:

      “Seems like Hindu caste would be the perfect avenue to explore that sort of variance.”

      Well maybe. I’d think castes were more to preserve something pre-existing than to create something new.

      I was imagining something else. A small group – maybe only a few thousand – of a pre-existing mercantile caste arrives in northern Italy from elsewhere and marries their way into the local equivalent, repeats the process over the next few generations in France and then Germany and once achieved goes back to being endogamous.

      Market acquisition by marriage.

      If they were average IQ 100-ish when they started – being originally a slice of the mercantile class from an average 90-ish environment and they then married into the IQ 110-ish (or higher) mercantile slice of an average 100-ish environment before going back to endogamy i’d have thought that would give them an initial boost.

  10. First four googo’ hits for “hindu caste IQ study”:

    the immortal “Indian/Chinese IQ Puzzle” thread at MR

  11. Sean says:

    “The hypothesis that the observed high intellectual achievement of Ashkenazi Jews is a result of natural selection for intelligence over the Middle Ages”. I don’t doubt it . But does Talmudic study have anything to do with it at all ? It seems you don’t think so.

    How did the teeming masses of the Chinese people as a whole get to be smart ? Given that the Chinese are no endogamous caste of moneylenders. (or borrowers, the Chinese blandly declined to borrow money at interest ) the 10,000 Year Explosion explanation for Jewish IQ is not very parsimonious. The Chinese had an long standing official exam system, but those they called ‘Dwarf Pirates’ or ‘Shrimp Barbarians’ ( the Japanese) did not. The prestige attached to scholarship was the explanation then, but why does that not explain Jewish IQ too?

    The 10,000 YE explanation requires the Sephardim to never have been much smarter than gentiles but the Sephardi suffered a setback to their development : their expulsion from Spain. They once were superior in IQ to gentiles. By my way of thinking the success of the Conversos leaves little doubt about their genetic superiority.

    An Ashkenazi noted for Talmudic scholarship received a range of valuable emoluments.
    1. A wealthy man’s daughter as wife, and a dowry that would secure their financial future
    2. Extremely high status in the community of a kind which brought economic benefits For example a ruling granted business monopolies on trade with gentiles to eminent scholars.
    3. Gifts, even if a scholar was well-off.
    4. Protection from anyone speaking against him ( no small advantage). This was enforced by bans and fines.

    • JayMan says:

      C&H’s hypothesis about Ashkenazi intelligence doesn’t necessarily have a bearing on how other groups evolved their current level of intelligence. East Asian and European IQ may be the result of selection to survive the harsh winters in those places. In addition, life during the Middle Ages may have applied selective pressures that favored increase of intelligence.

    • gcochran9 says:

      “Chinese blandly declined to borrow money at interest” . Evidence?

      As for the bit about prominent Talmudic scholars automatically acquiring a wealthy man’s daughter as wife, I’d be more inclined to take it seriously if someone would give me at least one example of this happening – better yet, some indication that it happened very often. The histories I read don’t mention it. At all. Moreover, if you bother to make a quantitative model, as you must if you are at all serious, it is easy to see that it is very difficult for a selective effect acting on a tiny fraction of the population to have much impact. Trust me on this.

      None of the non-Ashkenazi Jewish populations have exceptionally high average IQs today. Interestingly, Ashkenazi Jews in Israel generally seem to have thought that those other Jews (who mainly arrived in Israel after being expelled by Arab governments after 1948) were environmentally disadvantaged and would soon catch up, certainly by the second generation. But they didn’t. Many people expect this in other analogous situations and they are disappointed too. And surprised. Every time !

      Charles Murray argued for a mechanism selecting for high IQs among Jews that goes way back in time, well before the split between the Ashkenazim, Sephardim, Mizarhim, etc. This phenomenon – a generally high IQs among all Jews – does not even exist (Near and Middle Eastern Jews have scores well under 100) , so I am at a loss to understand why he said it. Maybe he was trying to prove his courage and independence of mind by publishing such a thesis in Commentary.

      You assume that respect for scholarship drove high IQs in East Asia. I think we don’t know that. I sure don’t.

      • Sean says:

        Talmudic scholarship was not the preserve of a few in the Jewish community of yesteryear.
        Being a scholar was a route to prestige and a good livelihood’

        “Is my mother-in-law paralyzed that I should have to earn a living?’

        Discoveries in science and mathematics are very good indications of intelligence. But there are other areas of mental achievement. The ability to convince people your right , even when you’re wrong, for example. Marx was descended from long lines of rabbis on both sides of his family, Freud was also descended from rabbis.

      • Sean says:

        A people that shall dwell alone, p. 242-243 i” There is also very clear evidence for eugenic practices among the
        19th-century Ashkenazim. Etkes (1989) finds that, although a variety of traits
        were important in the choice of sons-in-law, including appearance, health, and
        temperament, particular value was placed on the perceived potential for Torah
        study. In other words, marriage with the daughter of a wealthy man and
        consequent support of study during the years of adolescence (the kest period)
        were conditioned primarily on scholarly ability, and, indeed, the prospective
        father-in-law would give the future son-in-law an examination prior to agreeing
        to the marriage. The father-in-law would then support the couple for a specified
        period of years and provide a large dowry, which would secure the financial
        future of the couple.
        Katz (1961a) shows that scholarly ability was the summum bonum within the
        Jewish community–the ultimate resource when contemplating marriage.
        Wealthy individuals who were not themselves scholars could obtain scholarship
        indirectly by providing large dowries so that their daughters could marry
        scholars: “If an unlettered person married into a family of scholars, he would
        bask in the reflection of their glory” (p. 206). Moreover, in some cases, scholars
        could become wealthy simply as a result of their incomes and the many gifts
        they received. Individuals, such as the Court Jews of the 17th and 18th
        centuries, provided gifts and support for scholars. They thereby developed “the
        reputation of ‘cherishing the Torah,’ and the merit so acquired was equivalent to
        that achieved by study itself” (p. 206).
        Beginning in the ancient world, wealthy men would marry their daughters to
        promising scholars and support the couple until adulthood (Baron 1952b, 221).
        This practice became a religiously sanctioned policy and persisted among both
        the Ashkenazim (Katz 1961a) and the Sephardim (Neuman 1969).
        Katz (1961a) notes that this pattern of early marriage, and the associated period of
        prolonged dependency on adults (the kest period referred to above), was assured
        only to the wealthy@ […]

        (Here is an important point I missed before -MacDonald is heavy going)

        “As noted in Chapter 6, the officials of the Jewish community acted to regulate the marriages of the lower classes (Katz 1961a; Weinryb 1972), and the marriages of poor and indigent Jews came under special scrutiny by these officials (Hundert, 1986b). These regulations included minimum dowry payments, foregoing Jewish charity for a certain period, and numerical limits on the marriages of poor Jews”.

        (So the poor Ashkenazim didn’t just die off – their fertility was deliberately restricted).

        ” The result of these practices was a large overlap among scholarship, control
        of economic resources, social status, and, ultimately, fertility. Hundert (1992)
        notes that rabbis were often wealthy, socially prominent merchants,
        manufacturers, or traders. Throughout most of the 18th century, there was a
        Jewish aristocracy in Poland-Lithuania consisting of a small number of
        prominent families who “held an astonishing number of rabbinical and
        communal offices” (p. 117)”

        (Scholars were often also successful businessmen)

        Also “As in all traditional European societies (see, e.g., Herlihy & Klapische-Zuber
        1985), Hundert (1992) finds that there was a positive association between
        wealth and numbers of children in Jewish households in the 18th century, and
        Weinryb (1972) notes that there were marked differences in fertility among
        Jews, with successful business leaders, prominent rabbis, and community
        leaders having a large number of children reaching adulthood, while families of
        the poor were small. Vogel and Motulsky (1986, 609) note that in
        mid-18th-century Poland prominent Jews had 4-9 surviving children, while
        poorer Jewish families had 1.2-2.4 surviving children.”

        (“Mid-18th-century Poland” ? That’s a bit later than you’re hypothesising for purely natural selection. I’m not saying the 10,000 YE explanation is wrong, just that other factors were also important. )

    • Ortu Kan says:

      Sean said: the Chinese blandly declined to borrow money at interest

      That’s false. Consult this and this for discussions of intra- and inter-dynastic trends in interest rates and lending practices.

      Here’s a particularly colorful Tang dynasty episode that just so happens to involve a non-Chinese caste of moneylenders (how endogamous they were at the time I can’t really say):

      By the ninth century, the Uighurs’ domination of the money-lending profession in Chang’an had become notorious, and these foreigners were universally despised for their arrogance and contempt for Chinese law. In the early decades of the ninth century, as prices steadily rose, many Chinese businessmen and officials fell into debt to the Uighurs and were forced to pledge land, furniture, slaves, and even sacred relics or family heirlooms to their Turkic creditors. When a Uighur murdered a Chinese merchant in broad daylight, he was helped to escape by his chief while the Chinese government stood by helpless.

      Discussion of their ethnic identity and relation to present-day Uighurs/Uyghurs at link.

  12. Peter Frost says:

    Michael Caton,

    That kind of study was actually done, back in 1988:

    Kohn, H., P. Manowitz, M. Miller, and A. Kling. (1988). Neuropsychological deficits in obligatory heterozygotes for metachromatic leukodystrophy, Human Genetics, 79, 8-12

    The aim of the study was to find out whether Tay-Sachs and MLD heterozygotes suffered from reduced IQ:

    “Two groups of heterozygotes, one for metachromatic leukodystrophy (MLD) and the other for Tay-Sachs disease, were given a battery of neuropsychological tests, a standard neurological examination, and an EEG. Neurological and EEG findings were unremarkable for both groups. The MLD heterozygotes showed deficits in the neuropsychological tests involving spatial or constructional components, but not in tests involving language skills. The Tay-Sachs heterozygotes showed no consistent deficit on any component of the neuropsychological tests.”

    The authors also noted that academic performance was much better among Tay-Sach’s heterozygotes than among MLD heterozygotes :

    “However, there is a significant difference in the educational level achieved between the two groups. About two-thirds of the Tay-Sachs heterozygotes have education beyond high school, whereas only one third of the MLD heterozygotes have gone beyond high school.”

    I was able to contact one of the study’s authors, Dr Paul Manowitz. He told me that the data from this study were long gone. It’s a pity because it looks like the Tay-Sachs heterozygotes were a high IQ group.

  13. Thanks Peter. This is tantalizing, but it looks like all we can conclude strongly is that Tay-Sachs heterozygotes had no deficits, and that more than average (guessing that 2/3 is above average) went past high school, although it’s hard to say that without looking at non-carrier relatives as controls. If this is the closest, then it looks like the study has not been done.

  14. ghosthead@live.com says:

    Henry, Greg,

    One thing I would like your opinion on, which I don’t understand, is why the standard deviations in scores (in IQ tests or academic achievement tests) seems to remain identical in groups, even racially mixed groups.

    I mean, say we have a group with light pigmented skin and they all have a given level or variance, and then a group with very dark skin, and a given level of variance. And say these groups mix.

    Now in reality, as well as in theory, I understand that we would expect the mixed group to be more variable in pigmentation than the groups that constituted it.

    But in IQ, this doesn’t seem to be the case. When I have seem test data reported in the TIMSS or PISA or other breakdowns of achievement scores, mixed African Americans seem no more variable than White Americans on this trait, for example. Neither do Mestizo Hispanics. And in these groups, the admixture is not even evenly distributed within the group.

    I don’t understand how this is reconciled with within group variation or between group variation being mostly genetic.

    • Nice question. One route to an answer is that variances, and so SDs, have a large sampling error, so lots of the differences in SD that you see are just statistical flux and fleen.

      Even so, how big is the effect you are interested in? Let us mix two populations with IQ SDs of 15, one with a mean IQ of 110 and one with a mean IQ of 100, equal numbers of each origin population, randomly chosen, yaddle yaddle.

      The between group variance is 5^2 or 25 and the within group variance is 15^2 or 225, so the new total is 250 and the SD goes from 15 to 15.8, not much of a jump. You would need a very large sample to detect the difference.

      • GH says:


        I was sort of aware that increases in SD would be relatively small* for an aggregated population with separate IQs like you describe, and that a mixed population would show low increases in standard deviation even if it was only proportionate to that shown in the aggregated population (which I would guess would be the case if the two populations had the same functional alleles, but that it might be greater if they did not, depending on how disjoint(?) they were).

        I wasn’t aware about the dependence of SD on sample sizes and thought that it should obviously be visible on the tables of SAT results and other educational data that is put out. Whereas now I’m agnostic on that, not being aware of the kind of sample sizes that would be required or that are typically used.

        If variance does increase proportionately as in the above, it would seem like there would be some obvious social effects of that, e.g. a population of a mixed descent from equal numbers of IQ 95 and IQ 85 individuals would continue to produce as many of a given threshold high IQ as a population of IQ 95 individuals half its size (approximately, if I’m understanding correctly).

        (A dampener on the above would be if the alleles underlying between group IQ variation were strongly correlated with between group differences in the aspects of phenotype that serve as the most visually conspicuous population markers (that seems unlikely to me though).)

        Whether SD does increase proportionately (or superproportionately) rather than subproportionately (and I still really see no real reason why it would increase subproportionately) does seem like a relevant question. If (for just one example) you have a high performing population with 110 IQ that mixes with a lower performing population of 100 IQ, but the SD increases proportionately, you still have the same number of high performing individuals, so no problem, although there might be more effort in search for high performing individuals and networking between high performing individuals (which is a cost). If the SD does not increase, and does not increase proportionately, then that’s a bit of a problem.

        *Unfortunately in hindsight, not by personally through actually having the (rather basic now I see it) mathematical knowledge to perform the necessary calculation but through messily aggregating values from a couple of simulated normal distributions in a toy model in a spreadsheet.

  15. Peter Frost says:


    In a sense the study was done, but the authors didn’t feel the data were worth publishing. They just wanted to show that Tay-Sach’s heterozygotes were not below normal in IQ. Perhaps the lost data will turn up one day, on an old diskette left in a desk drawer.


    Contrary to the NY Times article, the academic gap between Burakumin and other Japanese has not changed, at least not since World War II:

    “According to research on Buraku pupil/students’ scholastic ability conducted in the post-war period, nearly 1 standard deviation difference in achievement scores was found between Burakumin and non-Burakumin pupil/students regardless of when and where the research was conducted. This meta-analysis on Buraku pupil/students’ scholastic ability leads us to conclude that the relative difference in scholastic achievements between the Burakumin and non-Burakumin pupil/student has been maintained to a considerable degree through the post-war period”



    But aren’t White Americans themselves a very diverse group?

    • GH says:

      I’d say diversity is relative and comparative.

      I wouldn’t think the European parental groups of White Americans would be as far apart in IQ means (or genes that underlie that) or particularly more variable between or within group than the European and African/Native American parental groups of Mexicans and African Americans. I haven’t ever heard that they are have been observably or measurably as dissimilar.

      • Peter Frost says:

        Some European countries have mean IQs in the low 100s and some in the low 90s. That’s a spread of 10 points. There is also considerable variability within some national groups, particularly those of Western Europe. I haven’t done the math, but my impression is that there is much more variability within and between European populations in IQ than there is within and between sub-Saharan African populations.

    • Porter says:

      Thanks for the link re the Burakumin. I was wondering if the “percentage vs standard deviation gap” issue was the explanation (as it usually is in supposed cases of closing test score gaps in the US).

      I suppose the Japanese-American immigrants could be a combination of selection and perhaps mixed descent (apparently intermarriage rates have greatly increased, and would tend to be higher in America).

  16. The fourth doorman of the apocalypse says:

    Brains are expensive organs. They are expensive developmentally, expensive for humans during birth and they require a lot of maintenance (energy, oxygen, etc).

    In an environment that does not involve interaction over long periods of time with large numbers of other humans (thousands …) it would seem that there would be selection against large brain size.

    On the other hand, some groups, like East Asians, have lived in large congregations for something like 4,000 years. Moreover, it would seem that downward mobility has exerted a strong influence on them for the last 2,000 years. The flushing of poor alleles from the gene pool must surely have had an effect.

  17. dave chamberlin says:

    Turning a globe in your hands you can’t help but notice that there are no booming economies on the equator. Why? The best answer I can come up with is human evolution in these regions is so pressured by newly mutated pathogens that evolution towards higher intellegence is muted. Gene transfer is vastly more likely (up to one million times one study showed) at tropical temperatures. Nature is constantly brewing nasty new germs tweaked just enough to resist antibodies where it is warm enough. To make an analogy a balloon isn’t going to blow west as far (evolution of higher intellegence) if the wind is blowing steadily from the north (evolution of new pathogens).

  18. Abelard Lindsey says:

    Cognitive ability clearly has a genetic component. However, there are areas that do not fit the HBD trend. Hawaii’s population is composed of people of mostly Asian backgrounds and Costa Rica’s population is mostly Caucasian background. Yet, both places have what can be politely described as sub-normal performance.

    • jb says:

      Is this actually true? I know that Hawaii is not exactly Singapore, but I was under the impression that if you were ranking “performance” Hawaii would rank above any Caribbean island (or indeed just about any black majority nation). In fact my impression — and I haven’t really researched this, so I could be wrong — is that there is essentially no overlap between the performance of diaspora East Asians and diaspora sub-Saharan Africans; i.e., the the worst performing Asians do better than the best performing blacks.

      As for Costa Rica, I just looked at its Wikipedia entry and learned that it “ranks first in the Happy Planet Index and is the “greenest” country in the world.” And I already knew it abolished its army way back, and seems to have benefited greatly by it. In fact, from the Wikipedia page anyway, Costa Rica comes across as the Portlandia of Latin America. Hardly “sub-normal!”

      • Abelard Lindsey says:

        40% of the state employees in Hawaii are illiterate.

      • jb says:

        I find it rather difficult to believe that “40% of the state employees in Hawaii are illiterate.” Can you provide a link? I’d also be interested in knowing the overall literacy rate in Hawaii. (If any American state were only 60% literate I think I would have heard of it by now).

        In any case, you didn’t actually address my objection, which is that compared to comparable islands around the world — in particular islands in the Caribbean with similar plantation origins — Hawaii is my no means “sub-normal.” And you have not contradicted the observation that the people of Costa Rica seem to enjoy a rather high quality of life. Neither place is perfect, but both do seem to fit the “HBD trend” of whites and Asians doing better than blacks and Amerindians in otherwise similar circumstances.

    • Greying Wanderer says:


      “The literacy rate in Costa Rica is 94.9%,”

      • Abelard Lindsey says:

        Something you will notice about Costa Ricans, if you have ever done business there, is that they are SLOW in everything that they do. It is true that the standard of living in Costa Rica is higher than any of the other Central American countries. However, it is lower than that of Mexico (Mexicans actually work hard).

    • sideways says:

      I suppose if you count Polynesians and Filipinos as “Asianw, yes, vbut you know they’re not what’s being discussed.

  19. Ralph Hitchens says:

    I believe we can thank the Internet that discussions such as this are taking place, even if publishing within academia is career suicide. If nothing else, the equatorial variable would seem to merit further study — linked, of course, to environmental factors.

    • dave chamberlin says:

      We have to kill the ignorant meme that discussions involving human diversity = racism. How do we go about this is a very interesting question. First and foremost we have to be realistic. It will take alot of time and quite frankly the whole conversation just flies over the head of average people. You can lead a stupid person to water, but you can’t make him think. If Joe Six Pack has a hard time understanding evolution than we just have to shrug, mutter WTF, and move on to folks who can grasp the concept that human diversity does not equal racism and work on them. It is happening, this change, Steven Pinker and other mainstream intellectuals are year by year approaching the subject with less trepidation.

      • jb says:

        It depends on how you define “racism.” If you equate racism with race hatred, then sure, HBD != racism. However from the point of view of many people, any assertion that different races differ in important ways, and in particular any assertion some races are superior to others (e.g., are more intelligent), is, by definition, racist.

        This particular way of defining “racism” is perfectly reasonable and coherent. The problem is the additional assumption that racism, defined this way, is also always hateful, and the further assumption that racist ideas, since they are hateful, must also always be untrue. The challenge is to get people to acknowledge that a statement can be at the same time both racist and true, and to accept that the issue of truth must take priority. That’s the meme I’d like to see propagated: “even if it’s racist, that doesn’t mean it’s wrong.”

      • Ron Pavellas says:

        @jb: my bias is to try to say all these things about race and differences so that a reasonable person will not perceive the communicator to be making odious or invidious comparisons, leaving room for valuing human life in general and also the lives of the individuals (or groups) under discussion. How to do this? I note you have used the stereotype “Joe Six-pack”. I admit to using expressions such as this, but privately, not in a discussion rooted in scientific inquiry. (Also, I admit one can argue about which persons are “reasonable” or not).

      • jb says:

        @Ron: Well you’ve put your finger on a problem.

        I’m a little concerned about your use of words like “invidious” — to my way of thinking the truth can be unwelcome or even hurtful, but it is never invidious. Still, there is a problem! It’s easy enough to say that group differences shouldn’t matter for individuals, because there is so much overlap between groups, and that individuals should always be judged on their own individual merits. This in entirely true, and in theory it resolves the issue.

        In practice however, once the reality of group differences became widely accepted, many people would feel a strong temptation to use those differences as shortcuts in evaluating individuals. This would of course be unfair, and it’s understandable for this reason alone that certain groups, and people sympathetic to those groups, might want to suppress knowledge of group differences, even if they inwardly suspected those differences were probably real. My own feeling is that we are always better off knowing the truth, but I do understand why others might think differently. So where does your loyalty lie? Would you favor suppressing truth if the truth was unavoidably hurtful to groups you felt sympathy towards?

        (BTW, it wasn’t me who used the term “Joe Six Pack”).

      • dave chamberlin says:

        @JB Maybe it is just semantics and/or personal opinion but I think the word racist simply needs to be dropped. Throwing around insults like Joe SixPack, or swear words like WTF may be unscientific and unprofessional but nothing stirs up anger like using the R word. I don’t mind how you define racism and use the word JB, you have a valid point. The word racism will always be associated with hatred, human misery, the absolute worst in people. If you say “even if it’s racist, that doesn’t mean it’s wrong” it is going to be taken out of the context, you are going to be shooting yourself in the foot in the world beyond this blog.

    • @JB:

      There is a complication to the idea that we can treat people as individuals and that the outcome would be fair. Here is a hypothetical example (variants of which come up all the time I think):

      I am hiring for a job, and there are two applicants that scored 140 on the IQ test that I gave them. I have found that the correlation between IQ and job performance in my shop is 0.70, that is to say the test is less than perfect. If I know nothing about either applicant save the test score then I can toss a coin. But imagine, instead, that I learn that one of the high scorers is an American Black guy, the other one is an Ashkenazi Jew. I can use this additional information to make a better choice, like this. The average IQ of the US Black population is 85, the average IQ of Ashkenazi Jews is 110. My best prediction is that in terms of job performance there will be regression to the mean, but knowing the group membership of my applicants means I know that they will regress to different means.

      My best guess now about the future job performance of the Black guy is 80 + 0.7 * (140-85) or about 119. My best guess about the future job performance of the Ashkenazi guy is 110 + 0.7 * (140-110) or 131. Bottom line: use the information about ethnicity and hire the Jew.

      The (ugly imho) bottom line is that ethnicity provides prior information and it is not at all irrational, from the viewpoint of my company’s profits, to discriminate.

      Note also that if the test I gave was perfect, rather than being only 70% perfect, the effect would go away and I should simply toss a coin.


      • jb says:


        I understand what you are saying, but does regression to the mean really apply here? You seem to be claiming that a black who scores 140 on an IQ test is — most likely — less capable then a Jew who scores 140 on the same test. It’s not clear to me why that should be so! Hasn’t it been shown that blacks and whites with comparable IQ scores exhibit comparable performance?

        Here is a thought experiment: Start with a large, homogeneous group with test scores normally distributed around a mean of 100. Now parcel the individuals into two disjoint groups, one with a mean of 85, and the other with a mean of 110. Make sure both groups still have high and low scorers. Now let’s say you had two job applicants with scores of 140, one from the low scoring group, and one from the high scoring group. Would you still expect them to regress towards the means of their respective groups? Remember, the tests were given while everyone still belonged to a single group. Why would it matter which group they were reassigned to after taking the test?

        (One possible problem with this argument is that it is not clear to me that you can parcel everyone into two normally distributed groups with different mean IQs, and perhaps that matters. I suspect you could do it with three groups though — one for the middle, and one for each wing — and the argument doesn’t change.)

      • billswift says:


        The point is that because the test is imperfect, the true IQ of the test takers will probably be lower than the scores, and because the mean IQ of the groups is different, they will probably be lower to differing degrees. In this case “regression to the mean” is talking about the error in the test scores regressing to the mean score.

      • harpend says:


        Interesting thought experiment, and I think you are right about what the outcome would be. But if we carried out your experiment, then let the two groups reproduce endogamously for a generation or two, the Central Limit Theorem would normalize the within group distributions (more or less well) and offspring would regress to the group means.

        It is well known that standardized tests overpredict the performance of US Blacks, and just this regression to a lower mean is the best explanation of the effect. (I say “well known” but I would have to dig for references. I remind myself of a lecture I heard years ago by a mathematician in which he said “There is a theorem that is well known to those who know it well”.)

        There is also chatter (I probably could find citations and data) that the offspring of high achieving US Black families underperform offspring of income and SES matched US Anglo families. Same thing.

        An anecdote: I taught at the University of New Mexico for a decade or so. The faculty were familiar with “Los Alamos kids”, offspring of scientists and mathematicians, who were a sharp bunch but most of whom had a keen sense that they were vaguely disappointments to their parents.

        Mechanically here is what is going on. If we pick someone who is super bright from a population, he is that way because he has a genome that is bright and also a positive environmental contribution to his brightness. Since what gets called environment is random as far as anyone knows, his offspring only get his genes, not his “bright” environment, and on average underperform him. In the same way, the folks that got 140 on my hypothetical IQ test, on average, had both high IQ genes and a good day or good luck guessing when they took the test.

        The effect is symmetrical, so if you are very bright your children on average will not be as bright as you are. On the other hand if you are really dull your children will on average be brighter than you are. So the brights are more or less condemned to being vaguely disappointed in their kids while the dulls will be proud of theirs, if either one cares about such things. Many do: university faculty in my experience obsess about their childrens’ SATs.

        BTW an even uglier implication of all this is what free meritocratic social mobility should do to us, essentially instant castes. I will write a proper post about this since several figures are necessary to get the point across.


        Thanks, you are right on, save that I would modify your first sentence to say that “the true IQ of the high scoring test takers will probably be lower than the scores”

      • jb says:


        I do understand regression to the mean, and the fact that the highest scorers have won both the genetic and environmental lotteries. But IQ scores are supposed to be repeatable, which means you should expect a person — black or white — who scores 140 today to score in the same range in the future. So an individual’s high scores can’t be a matter of “a good day or good luck guessing when they took the test.” The children of a high scoring black may not inherit his environmental good luck, but you’re not hiring the children. The high scorer himself should continue to enjoy the benefits of his environmental good luck (which occurred long before he took the test) after you hire him, and it seems to me that’s what ought to matter!

        This doesn’t make your argument wrong; just that the issue of regression to the mean between generations seems irrelevant to me. I do concede that if IQ tests correlate imperfectly with “true ability” (aka “g”?), and the normally distributed “true ability” of different groups varies, then it really would seem to make sense that a high scoring black would be more likely than a high scoring Jew to be scoring above his “true ability.” What I don’t understand is why this doesn’t apply equally to my model (before new generations are produced)! Is it possible that the relevant group for the high scoring black should not be “blacks in general” but rather “blacks who are capable of scoring 140 on an IQ test”?

      • harpend says:


        Thanks. Hard to keep all this stuff straight, in large part because my off-the-cuff example wasn’t laid out very well. When we talk about heritability we are talking about transmission of smart from one generation to the next. When I was talking about hiring for my business I was talking about transmission of IQ test score to productivity in my company. I said “same thing” somewhere, and they are sort of the same, but sort of not.

        So what I think I was assuming in my factory example was that the transmission from score to work output has two steps: test score to true IQ, then true IQ to productivity. If we know group membership we can sharpen up our estimate of the first step by using group membership as prior information is Bayes’ sense.

        Even without bringing in different groups, IQ test scores are not all that replicable. I have seen an estimate that the correlation between your score today and your score a year from today is only about .85 or so, i.e. close to the correlation between test scores of identical twins.

        Thus I disagree with this statement of yours: “The high scorer himself should continue to enjoy the benefits of his environmental good luck (which occurred long before he took the test)”. Words are tricking us: in quantitative genetic usage environment just means error while informal North American usage usually means books in the home, Mozart in the womb, getting health care, and so on. So I would not say that environmental effects took place long before he took the test.

      • billswift says:

        >I would modify your first sentence to say that “the true IQ of the high scoring test takers will probably be lower than the scores”

        Well, sure, in general. But I wasn’t speaking in general, only about the two test takers in the example.

      • JayMan says:

        The overprediction of the performance of non-Asian minorities by SAT tests was brought to light by Robert Klitgaard in his 1985 book Choosing Elites. There he states that you’d need to subtract 240 points from the combined SAT scores of Blacks for these scores to have the same predictiveness of school performance as they do for Whites.

        However, Satoshi Kanazawa looked at income of Blacks vs non-Blacks in America and found that Blacks earn more than Whites when IQ is controlled. This suggests that affirmative action is responsible for the overprediction Black performance by their test scores.

        The other factor that I haven’t seen anyone consider is personality. Richard Lynn once pointed out that even when matched for IQ, Blacks commit crime at a higher rate than Whites. This suggests lower conscientiousness and higher impulsivity that may negatively impact school/job performance. Of course, regression to the mean due to test error might explain this as well.

      • Cubano says:

        It would not be irrational for my company to discriminate. Neither it would be irrational for a medical insurance company to decide not to cover an individual for a group of diseases like let’s say “Tay-Sachs disease” because it is known to be more common in his ethnic group. But now, would that be unfair?
        Since the final value for true IQ is greatly influenced by the correlation factor (0.7), and probably too by the other 0.85 factor (being a two-step process), it would be in the best interest of the company to try to improve the accuracy of my IQ test instead of just discriminating by ethnicity.
        In the calculations above, choosing 80 instead of 85 increased the difference to 11 points where it should have been only 7.5, perhaps I didn’t understand the numbers well.

  20. David says:

    I have always thought that Jewish intelligence arose because of negative selection–the constant sloughing off of the least successful members of the group. Medieval Rabbis required that young people have a house paid for before they could marry. Rich merchants gave their children houses so that they could watch their grandchildren grow up. Poor schlemiels couldn’t marry at all, but another option was always available–just stop being a Jew and assimilate.

    • gcochran9 says:

      As long as poor Jews had substantially lower fertility than wealthy Jews – which looks certain – our proposed selective mechanism was operating. No need for conversion, and what little evidence we have suggest that there wasn’t much, at least among the Ashkenazim.

      Assimilation was harder than you think.

  21. Cubano says:

    In 10 000 year Explosion and here in the quote by Neil Risch there are references to the Latino IQ averages or academic performances. I’m very curious of how do you come up with a meaningful comparison between IQ scores of let’s say “Whites” and such a diverse group as Latinos (which include all three major racial groups and their various mixtures). How do we come up with a Latino IQ? Could it be that of Mexican (Spaniard-Native American) descendents if we perform the study in California or Puerto Rican (Spaniard-Sub saharan Africans) descendants in New York? It seems to me that the “Latino IQ” is a pretty shaky number to use as a basis for comparison.

  22. panjoomby says:

    I second Ralph Hitchens. Thanks for the discussion above!
    NB: in low-IQ groups there’s less room to vary, so their std. deviation tends to be smaller (e.g., a sample of mentally retarded/intellectually disabled will have less than a 15-point std. deviation). Similarly, among a sub saharan african sample we can expect a smaller std. dev.) In high-scoring groups there’s more room to vary. We would expect some regression to the mean on achievement (for cultural reasons this would be so for the MR/ID sample, since they have been exposed to education/reading, but this would not be quite so for the sub saharan african sample, etc.)

  23. Ron Pavellas says:

    Are cognitive skills (as measure by standard western IQ test) less useful (historically, say before western and Arab colonialization ) to survival and fitness in equatorial regions than in temperate regions?

    • gcochran9 says:

      Maybe. At least you can construct plausible scenarios in which that is the case. Let us suppose that, in some part of the Old World tropics, over a long period, people were more likely to suffer from, die from, infectious diseases than people in a colder, dryer part of the world. Infectious disease played a bigger role in determining fitness. Let us also suppose that the nature of those diseases was not understood well enough that relatively smart people survived them much better than anyone else. This was true, I think, for falciparum malaria: we didn’t really understand how it was transmitted until the 1890s. So the payoff (in terms of increased numbers of surviving offspring) for intelligence was, all else equal, lower there. More of the important events in life were uncontrollable by conscious action. Along the same line of thought, imagine a world in which most deaths were caused by being hit by a meteorite: what use high IQ?

      If brains were just as costly (metabolically), but had a lower payoff in a high-disease environment, you would expect brains to be smaller in that environment, and IQ lower.
      And this is the case.

      But although possible, this idea is by no means proven. The weather was drier and colder during the ice ages: probably pathogens were less important then than they are today. There are parts of Africa that are high and/or dry, hence have a lower pathogen load: but the IQ scores there don’t look much different from the rest of Africa. Population density increased in peoples that adopted agriculture, and infectious diseases did as well: did the trends reverse? Falciparum malaria is the most serious infectious disease in the world, and looks to be only a few thousand years old. Has it had an effect on human intelligence during that time period? Maybe – we don’t know.

      • dave chamberlin says:

        I would pose the question differently. Would evolution move slower on one attribute (in this case increased cognitive skills) if their was increased pressure to adapt to an unrelated attribute (quicker evolution of pathogens).

      • teageegeepea says:

        William McNeill made the point about the uselessness of intelligence as a defense against “microparasites” way back in “Plagues and Peoples”.

      • dave chamberlin says:

        @gchochran “There are parts of Africa that are high and/dry, hence have a lower pathogen load: but the IQ scores there don’t look much different from the rest of Africa.” Tis true, but it is in these locations we find find the bones of the first anotomically modern man starting around 160,000 years ago,

    • harpend says:

      @dave chamberlain

      Yes, absolutely. Think of an XY graph where the X-axis is pathogen resistance and the Y axis is cognitive skill. If there is no pathogen problem the direction of evolution is “up”, i.e. purely in favor of cognitive skill. But if the intensity of selection is equal for cognitive skill and pathogen resistance then selection is in the NE direction, and intensity of selection on each trait is about 71% as strong as it would be if there was only one trait under selection. (71% being the cosine of 45 degrees.)

      • dave chamberlin says:

        If the Harpending Cochran team end up running with this concept, meaning they flesh it out further in the scientific format I would feel honored.

  24. mnnllg@yahoo.com says:

    Joe Six Pack is quite aware that there is human biodiversity, even if he hasn’t assigned what he knows a name, even if he has not heard the term “human biodiversity.” He watches (and has played) enough sports, has worked at enough jobs, has lived long enough that the idea that groups differ in many ways, including intelligence, is no surprise to him. Hell, he’ll even tell you what he thinks. Joe believes his eyes tell him the truth and he doesn’t worry about being pc. Joe is a believer in experience.

    It’s Joe College with whom you must learn to communicate.

  25. Kiwiguy says:

    ***Joe is a believer in experience.

    It’s Joe College with whom you must learn to communicate.***

    This reminds me that magicians apparently report that it is easier to deceive more intelligent, better educated audiences. This may be because with greater absract reasoning skills they can come up with complex explanations rather than seeing the obvious.

    • Greying Wanderer says:

      I wonder about the abstract thing too. I’ve known lots of stupid people who were very good at certain very practical things: poaching, stealing cars, working with animals, some mechanical work but not anything electrical or electronic but who went completely blank at any form of abstraction – which might be connected somehow to them also having a very short time horizon.

      They’re at the edge of functional in the modern world but i wonder if a very low IQ might be fine for foragers or herders in a pre-literate world. I mean, what would they need IQ for? Although it may be true in theory that high IQ > low IQ at performing all tasks the comparative advantage will drop the simpler the task.

      • Ron Pavellas says:

        If you look at the Myers-Briggs Type Indicator (MBTI) for psychological profiling (a well-regarded and widely used psychological profiling tool) you will see that (in the USA) approximately 75% of the people have a “preference” for non-abstract information (“sensing”, in the MBTI terminology) and approximately 25% “prefer” or are more adept at processing abstract information (“intuitive”). I believe the 16 types (within four groupings) do correlate with “IQ” measures, but I can’t find this quickly on the Internet. Whether any given type is more “intelligent” than any other, it seems to me, depends on what one is trying to accomplish.

      • JayMan says:

        Satoshi Kanazawa wondered the same thing. He discusses a theory by Bruce G. Charlton that posits that intelligent people evolved to apply their higher analytical abilities to the social realm where simple and more primitive intuitive insight (aka, common sense) would be sufficient. Charlton even goes as far to propose that this is a form of “peacocking” by intelligent individuals. As a way of showing off their intelligence, intelligent people, according to Charlton, concoct overly complicated (and wrong) theories about behavior to demonstrate that their level of privilege is such that they can devote brainpower to such wasteful purposes (think: philosophers).

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  30. Anonymous says:

    As always, Cochran provides a clever, but incomplete analysis. The real story of Jews over 2,000 years is the diaspora. Jews constituted 10% of the Roman population. This means (I am guesstimating) 90% of the jews “vanished.” Therefore, dumb Jews became Christians, Muslims or died prematurely. The answer to your riddle lies in the missing Jews. Scholarly Jews remained Jews. You can flesh my ideas to your heart’s content.

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