Selecting for intelligence

Mike Smith relays an interesting possible explanation for the observed
statistical fact that American and European Jews have a mean IQ a
standard deviation higher than Caucasian gentiles:

During the period from ancient times to modern times, there was a
constant phenomenon of Jews converting to Christianity (there were
many social pressures to do so). In a nutshell, the idea is that the
lower-IQ Jews were statistically more likely to convert, as it freed
them from having to learn to read Torah. During the Middle Ages, it
was not worth the effort for most people to become literate; the
payback was not worth it. Books were rare and expensive, and learning
to read was no guarantee of getting ahead in life. Of course, people
like to do what they’re especially good at, and the higher-IQ’s among
the Jews did not find learning to read to be such a burden. As such,
they were statistically less likely to convert (and statistically more
likely to become fathers of many children in a culture that valued
intelligence.) It is worth noting that in ancient times, Jews were not
stereotyped as especially intelligent; that stereotype arose in the
Middle Ages.

This is a special case of one of my favorite Damned Ideas, originally
developed by John W. Campbell in the 1960s from some speculations
by a forgotten French anthropologist. Campbell proposed that the
manhood initiation rituals found in many primitive tribes are a
selective machine designed to permit adulthood and reproduction only
to those who can demonstrate verbal fluency and the ability to override
instinctive fears on verbal command.

Campbell suggests that all living humans are descended from groups
of hominids that, having evolved full-human mental capability in some
of their members, found the overhead of supporting the dullards too
high. So they began selecting for traits correlated with intelligence
through initiation rituals timed for just as their offspring were
achieving reproductive capacity; losers got driven out, or possibly
killed and eaten.

Campbell pointed out that the common elements of tribal initiations
are (a) scarring or cicatricing of the skin, opening the way for
lethal infections, (b) alteration or mutilation of the genitals,
threatening the ability to reproduce, and (b) alteration of the mouth
and teeth, threatening the ability to eat. These seem particularly
well optimized for inducing maximum instinctive fear in the subject
while actually being relatively safe under controlled and relatively
hygenic conditions. The core test of initiation is this: can the
subject conquer fear and submit to the initiation on the basis
of learned (verbal, in preliterate societies) command?

Campbell noticed the first order effect was to shift the mean of
the IQ bell curve upwards over generations. The second-order effect,
which if he noticed he didn’t talk about, was to start an arms race in
initiation rituals; competing bands experimented with different
selective filters (not consciously but through random variation).
Setting the bar too low or too high would create a bad tradeoff
between IQ selectivity and maintaining raw reproductive capacity. So
we’re descended from the hominids who found the right tradeoff to push
their mean IQ up as rapidly as possible and outcompeted the groups
that chose less well.

It doesn’t seem to have occurred to Campbell or his sources, but
this theory explains why initiation rituals for girls are a rare and
usually post-literate phenomenon. Male reproductive capacity is
cheap; a healthy young man can impregnate several young women a day,
and healthy young men are instinct-wired to do exactly that whenever
they can get away with it. Female reproductive capacity, on
the other hand, is scarce and precious. So it makes sense to select
the boys ruthlessly and give the girls a pass. Of course if you push
this too far you don’t get enough hunters and fighters, but the right
tradeoff pretty clearly is not 1-to-1.

(This would also explain why humans are designed for mild polygyny,
1 to 3 sexual partners per male. You can spot this by looking at
where human beings are on various physical characteristics that
correlate with degree of polygyny in other primates — disparity in
average size between males and females, for example, is strongly
correlated with it.)

What Campbell did notice is that this theory of selection
by initiation would neatly explain one of the mysteries of human
paleoanthropology — how human beings got so smart so fast. The
differences between H. Erectus and H. Sapiens are not large in
absolute genetic terms (they can’t be, we share over 94% of our genome
with chimps) but they’re hard to credit given normal rates of
morphological change in mammals and only two million years to work
in. Something must have been putting hominids under
abnormally strong selective pressure — and Campbell’s idea
is that we did it to ourselves!

Now, I’m not sure I believe Jews bootstrapping themselves up a
whole standard deviation in less than 2000 years, but if you apply
a similar idea to a longer timeframe it begins to look pretty
reasonable. (And Campbell did suggest that the Jewish practice of
infant circumcision had originally been a manhood rite.)

Within my lifetime, I expect we’re going to have the ability to do
germ-line enhancement of human intelligence. I strongly suspect that that
will set off another arms race — because cultures that suppress
that technology will be once again doomed against cultures that do. And
this time, we’re smart enough to know that in advance…

Categorized as Science


  1. I’ve always thought that there was a nother significant factor involved: the goyim spent over a thousand years breeding *against* intelligence. When you insist on making your most intelligent people take vows of celibacy, it’s not going to help your average IQ.

  2. Also note that the jewish subpopulations with the higher IQ scores have high incidences of certain neurological disorders. It may not be a pure improvement so much as a different equilibrium point due to different selection pressures; ‘overclocking’ in response to a strong pressure for intellegence at almost any cost.

    (There was some discussion of this on Jerry Pournelle’s blog a few months back.)

  3. From what I’ve heard, Catholic celibacy for priests wasn’t especially much enforced for most of that thousand years, and medieval priests weren’t necessarily the most intelligent men–they were more likely to be “excess” sons.

  4. I believe Nancy is correct about this.
    Priestly celibacy wasn’t taken very seriously until after the Reformation, so it was a late and partial development.

  5. It occurs to me that another reason for the smarter Jew is that persecution has meant that dumber Jews will tend to be pogrommed (along with their offspring) while smarter ones would see the writing on the wall and manage to get out of town before the pogrom started.

    It should be no surprise that there would be some difference in terms of survival skills. At ~4 generations a century and a couple of millenia of persecution there is some 80 generations of breeding and culling (either by pogrom or conversion) for high survival genes which is plenty of time to see a significant difference.

  6. This stuff is so damned hypothetical. I don’t know what proportion of Jews converted to Christianity in various eras, nor what sort of people they were. I’m betting on at least a bimodal distribution: some who weren’t bright enough to get respect for learning Talmud and some pragmatic folks who didn’t care much about religion and preferred being insiders (was that possible?) and/or not being persecuted (which didn’t work reliably, but may have worked some of the time).

    I have no idea what proportion of Jews were killed in pogroms, nor how feasible it was to avoid the risk by intelligent prediction. I will note that moving to Germany seemed like a good idea at the time, and may have been a better idea than living in Poland.

    Here are my two theories for that difference in test scores. Note that one is non-genetic and the other is possibly genetic, but not a matter of having genes for more intelligence. (I’ve already posted these to Gene Expression.)

    The first is that traditional orthodox Judaism is the only culture I know of where intelligence (logic and memory) is a primary means of male competition. Even though the proportion of Jews who go in for Talmudic disputation has dropped precipitously, the cultural effects remain.

    As for genetic effects, they’re not as obvious as you might think. From casual reading, I think the pattern was that everyone was encouraged to get married and have children. However, a poor boy who was good at Talmud could increase his chances of marrying the daughter of a rich man, who’d get status from supporting the family. Again, I don’t have actual statistics: How often did it happen? Was the grandfather’s fortunes likely to be stable enough to give his grandchildren a good start in life?

    In particular, Jewish parents are as pleased to have a smart child as mainstream American parents are to have an athletic child. There are no social penalties for showing that one is intelligent. (OK, I’m generalizing wildly, but this matches what I’ve seen. There are non-Jewish American sub-cultures and families like that, but I get the impression it’s far from universal, and though the proportion is increasing, that change is relatively recent.)

    Yes, some people fight off being abused for their abilities and go on to great accomplishment. However, not everyone does (probably not the majority), and that drags down the average.

    So, there’s that psychological effect + the results of Jews being more likely to give their kids an intellectually enriched (or at least not deprived) environment.

    The other one is that Jews tend not to be serious drinkers and/or alcoholics. (I was just going on observation and little facts there–someone at Gene Expression turned up a study showing that 20% of Jews have a gene that makes drinking a lot less fun. Any thoughts about how a 20% genetic difference would shape a culture? That’s a real question–it’s not a majority, but it might make a difference.

    Whether the relative non-drinking is genetic or not, having a culture where there’s no social obligation to get soused will probably going to lead to more time spent thinking.

    Mike Earl: In re the “certain neurological disorders” being more common in the Jewish populations with the higher IQs: What do you have in mind? Tay Sachs is pretty rare, but at least I’ve heard of it. The gene that causes serious muscle problems sometimes but reliably causes higher IQ is so rare I’d never heard of it till recently.

    The only neurological disorder that I’d say is common among the Jews I know is depression, and I have no idea whether it corelates well with intelligence.

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  8. Smith’s theory appears to have several flaws.

    The lower-IQ Jews were statistically more likely to convert, as it freed them from having to learn to read Torah.

    This premise implies that the IQ could have been tested prior to conversion. Otherwise, how do they know that it was the lower-IQ Jews who converted?

    The higher-IQ’s among the Jews did not find learning to read to be such a burden.

    This premise implies that aptitude for learning a particular skill (reading) is a result of a high-IQ. Whether or not this is true, it doesn’t explain the other aptitudes (i.e., mathematical prowess) that does not directly relate to linguistic ability.

    As such, they were statistically less likely to convert.

    This is simply circular reasoning. The first premise relies on the assumption that the Jews who convert have low IQs. Therefore, if someone has a high IQ (e.g., has an aptitude for reading) then they are less likely to convert.

  9. The first is that traditional orthodox Judaism is the only culture I know of where intelligence (logic and memory) is a primary means of male competition. Even though the proportion of Jews who go in for Talmudic disputation has dropped precipitously, the cultural effects remain.”

    brahmins, chinese.

  10. Celibate priests might have been able to get more resources for their relatives. There’s a famous picture of Cardinal Mazarin on his deathbed surrounded by numerous relatives. None of those relatives had any worries about going hungry.

  11. An upcoming paper by Gregory M. Cochran and Henry Harpending will address the relationship between some Ashkenazi hereditary diseases and higher IQ, and offer a theory of the Darwinian selection pressure that could account for this.

  12. An alternate scenario is that the initiation rites selected for group loyalty and courage. ( The following is all subjunctive mode ) The intelligence filter operated on the losers. Many perished but a few could survive by charming the women and getting baubles and reproductive opportunities. The groups would alternatively drive the parasites off in times of scarcity or enlist them when massively attacked from outside when a bad warrior might be better than no warrior. When these satellite men did succeed in breeding their genes spread through the group and the selective bar kept getting higher. This is suggested by recent studies of satellite male communities in fish, butterflies and birds.


  13. I think people here are going way over the top.

    Look, genetics and Darwinism is “the fashionable theory today”, and explaining everything through evolutionary processes is the “error in vogue”. People use to do the same all the time, you know. The same happened with Freud at some time.

    And, of course, everyone likes to see oneself in a good light. If you endorsed the inherent superior intelligence and overwhelming maleness of the Spaniard, I would be tempted to endorse the idea :-P

    So, summing up all I will write, my caveats to your theory are two: First, the scientific basis of the statement is bad even for a hypothesis. Second, if the Jews had been inadvertedly bootstrapping themselves for anything (which they have not), it would have been for stupidity and failure. “Jewish intelligence” is nurture, not nature.

  14. The Campbell theories you mention (which lack any proof) at least refer to processes taking place during a much longer period of time. Evolution takes a lot of generations (probably not enough in the Jew’s case) and a separate environment for a specific group to evolve in.

    You could argue that the Jews did have a separate environment as they only married into their religion for a long time (more due to external prohibitions than due to other causes, as a man/woman in love could have converted into/out of Judaism in order to marry). But of course this is ignoring the fact that the mating partners are not always the relationship partners, something evolutionary psychologists are fond of repeating.

  15. In medieval Spain, in spite of and Jewish exclusivism, and of the prohibitions of the laws, there are many recorded cases of mixed marriages between Jews and Christians.

    Another error you commit is assuming that all medieval Jews were forced to study the Torah to the point of having to convert to Christianity to escape from this duty. And that that was the main reason for converting.

    Indeed learning by rote and study of the Torah has always been a given in the education of Jews, and it can be considered a gruelling, repetitive and boring task. But not all Jewish children are destined to be rabbis, and I don’t think this would have been a problem for people of the adult age (when one has the freedom of abandoning judaism).
    But it is also a task quite against what you yourself have called the “hacker mentality”. You don’t have to be unintelligent to loathe rabbinic studies, and an unimaginative, non-creative person with force of will can acquire literacy and learn by heart lots of text.

  16. The real perks of conversion to Christianity were of course those of being free from persecution. But these were higher for those of more social status and ability between the Jews.
    A jewish commoner (like a city artisan) would be better looked upon by Christians and loathed by Jews. The new “converso” –converted- would perhaps avoid some taxes and make his life easier if he converted (I write “he”, because women of every religion were rarely their own masters throughout history). But his status and means of living would stay more or less the same.
    In contrast a wealthy, successful Jew had much more to gain from a conversion. Jews who held state offices (such as that of Alfaquí, or Treasurer) would be peered and given a better post.
    Between the most egregious conversos is Salomón Halevi, greater rabbi of Burgos, who turned with all its family to Christianity in 1390, adopting the name of Pablo of Santa Maria. He got to be Lord Chancellor of Castile and bishop of Burgos. With the characteristic tenacity of the conversos, he dedicated great part of his energies and intellectual capacity to the persecution of its former brothers. This man accused the Jews, after his conversion, of adapting the prophecy of Jacob (the sceptre would not taken from Judah) to Spain, that is, of plotting the foundation and government of a new Jerusalem.
    Incidentally, to him was due lots of legislation restricting the activities of the Jews. The infamous inquisitor Torquemada also had Jewish ancestors. It is well known that people who are bon again to an opposing religion are most often the most radical fanatics.

  17. This phenomenon (the more brilliant Jews abandoning Judaism) is not restricted to medieval Spain. Many of the Jewish intellectuals in the XIXth and early XXth century Europe mentioned here were not religious or, like Heine and Marx officially converted out of Judaism.

    This is a well known phenomenon: Secularisation was in some occasions nothing more than the subduing of Judaism or its forfeiture in order to attain a better status. Here we find the same phenomenon: Those who were more gifted and talented, or those of a higher social status, had more to gain from abandoning Judaism (whereas it was not the intelligent but those who were more inmovilistic and traditionalistic who would have found sticking to Judaism more appealing). Wealthy Jewish German bankers routinely married their children into broke noble families, and paid the price of conversion for it.

  18. “Thus, assimilated Jews have a particular propensity for constructing secular messianisms — or for elaborating and intellectualizing secular messianisms invented by gentiles.”


  19. To clarify, while I believe natural selection explains a lot I have caveats about IQ
    as a tool for testing intelligence. If you can’t measure the coast of France
    with a single number how can you do it with human intelligence?

    Recently I read the obit for an African field biologist. His western colleagues
    were in awe of his ability to provide rare specimens. I wonder what the bell curve
    would be for Anglos on an IQ test based on practical hunting skills?

  20. J.P. Carter wrote, in part:

    >> Smith’s theory appears to have several flaws

    Well, it’s not my theory, I was just relaying it.

    Carter also wrote:

    >> This is simply circular reasoning.

    You may make it appear so by eliminating my frequent use of the term “statistical”. But I find your comment interesting for this reason:

    I did imply a feedback loop when I said “people like to do what they’re good at”. And, of course, people become good at what they like to do.

    I stand by this. Feedback loops exist in nature, and cannot be dismissed as “circular reasoning”.

  21. Study of talmud (jewish law) involves a lot clever argument construction and deconstruction. Anyone who thinks it is boring has not been doing it right. If you love logic, you will enjoy the mental jousting involved in Torah/Talmud study. It helps to learn it from a rabbi, in a group of 3-7 people. Most rabbis who lead this type of “study session” are also very interested in the subject and the logic. And teachers who think their subject is interesting make the subject more interesting.

  22. razib you mention the brahmins and chinese as cultures where intelligence is a primary means of male competition. These two groups also have statistically higher IQs. I guess this gives some more support for the theory.

  23. “”An upcoming paper by Gregory M. Cochran and Henry Harpending will address the relationship between some Ashkenazi hereditary diseases and higher IQ, and offer a theory of the Darwinian selection pressure that could account for this.”” – I fully disagree with this paper. Read it and you will know what I mean…

  24. IQ allegedly measures an organisms ability to adapt to its environment and is even more loosely equated with general Intelligence but that is generally speaking nonense – and is is predominately infiltrated with a rationalist and class skewed analysis of mental capability – after all take the case of a sinpleton who grows up in a home where chess is played and discussed and analyzed and books and chess clubs and with schools and tutors devoted primatily to the imparting the intricacies of this board game then test this simpleton and compare his score with someone who doesn’t even know how to move the pieces and even if they are whizzes at differential calculus, euclidian geometry and speak arabic and chinese fluently they will probably get a much lower score on the Chess IQ test than the simpleton – of course you might argue that IQ deals with a much broader range of thinking capabilities sut someone who is unfamiliar with the Games is usually going to come up way below those who have been encouraged to master the Games from an early age irrespective of any innate abilities

  25. I reject the idea that the capability to control fear represents a selective mechanism. Any naturalist knows that fear is a positively selecting instinct in most natural demes. A major premise of your blog entry is that intelligence enables you to control fear, or leads to a less fearful state under stressful conditions. I’d love to see some emperical, hell, even subjective, evidence of that….

    To my way of thinking, being a more intelligent person allows you to see obscure patterns more clearly, including those that may represent danger. In that sense, intelligence allows you to AVOID dangerous situations, not gain a simpletonic dismissal of instinctive fear.

    My 10 cents.

  26. Can intelligence really be determined by an IQ test? Furthermore, I don’t believe there is enough evidence to support the borderline facist-like pride for the higher scores. How many subjects were in this study? What were the error values?

  27. You could apply this theory to the English/American puritan period as well. The average puritan read 15-20 chapters of the Bible a day and trained their children to do so as soon as they were able to read. This was not due to “natural selection”, but to habitual intellectual routines that forced them to use their brains and to pass this down to their children. They were not limited to the Bible only, but their education included much information in the liberal arts. A good example is Jonathan Edwards who catechized all his children and all if not most of them all became doctors and lawyers.

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