Myriad Ways

Rushton thought that the explanation of geographical variation in IQ was adaptation to a world with winters.  I didn’t think that was crazy, but I was pretty sure I could come up with ten other comparably plausible explanations.   In some, the key events might have happened tens of thousands of years ago, while others might have been recent enough to be documented in the historical record.

Increasingly, I suspect that there is no single explanation.  Maybe several of my  notions are partly true.  The Ashkenazi Jews look like a case of recent selection for white-collarism in a reproductively closed merchant caste – and maybe there are similar explanations for the Parsees and some of the high Indian castes.   Cousin marriage explains some of what we see in places like Iraq or Uttar Pradesh.  Increased genetic load resulting from high average paternal age among polygamists probably plays a role in sub-Saharan Africa and Australia.  Adaptive introgression from Neanderthals?  Could be.  Increased population size among agriculturalists, resulting in Fisherian acceleration?  Possible: certainly civilized peoples generally beat out hunter-gatherers. Iodine shortages?  Surely.   Brain damage from capsaicin?  You know it.

Pygmies apparently score very poorly on cognitive tests. I wonder if that’s a side effect of being small: small brains must have lower performance, all else equal. Something about rain forest environments must select for pygmyism, since that phenotype has apparently evolved independently a number of times.  That may be yet another path leading to low IQ.





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33 Responses to Myriad Ways

  1. Donald Templer wrote in Personal and Individual Differences, I think last year, that “challenge” is the best explanatory word for the different kinds of selection pressure that partly explain higher IQs, and cold winters might be one challenge in the past, and the AJ:s white collar adaption might be another. But there should be more things to consider.

    • Personality, not “Personal” – I wrote too fast.

      • John Harvey says:

        Most animals have a raft of instinctive behavioural traits which have evolved to preserve and propogate them. For any given species these traits will have evolved in harmony with each other to a large, (but not total) extent. If an individual member of the species develops intelligence of some sort then he will tend to use that ability to ignore some of his institncts and manipulate his environment to his short term favour. But in doing so he will also, to some extent, disrupt the evolved balance between his instincts and his environment. This may well be detrimental to his survival, e.g. the particular gazelle blessed with a modicom of reasoning who decides to ignore his instincts and try to negotiate with the lion. Most examples of evolving intelligence may be like this – out of balance with the individual’s instincts and as such counterproductive. They will be bred out of the population.
        But there may also be some critical point beyond which the benefits of intelligence begin to outweigh the drawbacks, and it may be that humans are the only species who have managed to claw their way past this point.
        But then again it may not be, and perhaps we have only delayed the inevitable. It is well documented that in today’s world the brightest people tend to have the fewest kids – a counter-survival strategy if ever there was one. A large element in this dysgenic process has been the attraction of careers or other passtimes which involve making great use of the intellect, and which hence leave little or no time for or inclination to breed, e.g. in extremis the hermit genius devoted to his research but socially isolated as a result.
        If pygmies have lower IQs this may well be because the set of instincts which drive them may be particularly well attuned to the environment in which they find themselves, and as such they have survived and bred. In such circumstances the evolution, for whatever reason, of higher intelligence in them could well have been counter-productive.

      • Paul Jaminet says:

        Re John Harvey’s comment, in many ways humans may run afoul of the mechanism he describes: our intelligence allows us to rationalize stupidity and ignore intuitions that would often serve us better than our ideas.
        I think this suggests that intelligence evolved not to promote thinking, but rather to promote sociability — an ability to understand and communicate with others — and intelligence is a byproduct. Intelligence may have been specifically selected in some peoples like the Ashkenazi Jews (with unclear results for long-term fitness; the Ashkenazi share of population may have declined over time), but in most peoples it is not the primary determinant of fitness.
        It’s possible that the most evolutionarily fit IQ is the population mean plus 1 standard deviation — excessively high IQs may inhibit social success which is probably the main driving factor in fitness.

  2. JayMan says:

    A couple of additional thoughts on the matter:

    Peter Frost saying much the same: Evo and Proud: Now what? – including a possible explanation of the apparent association between dark skin and aggression.

    Me, on why IQ appears to be correlated with latitude: IQ Ceilings? « JayMan’s Blog

    Some of my ideas how average IQs evolved across Europe (including my neat little map :) ): More on Farming and Inheritance Systems – Part I: IQ | JayMan’s Blog

    On that last point, by the way, see HBD Chick for her recent discussion of Southeastern Europe: the zadruga « hbd* chick

  3. asdf says:

    “Brain damage from capsaicin.”

    Can you elaborate on this? I hadn’t heard of it before and a quick Google search didn’t turn up much.

  4. Another clear tendency is for certain religious sects to have lots of children, see Eric Kaufmann: ‘Shall the Religious Inherit the Earth?’

    Although membership in such sects is a culturally rather than genetically inherited trait, I suspect that people with a genetically influenced propensity to be religious will be less likely to leave such sects and more likely to accept the command to multiply and be fruitful. Thus we may be evolving, genetically as well as culturally, toward more religiosity.

    As for the effect of this on intelligence, it’s certainly possible to be religious and highly intelligent at the same time, but I would nonetheless expect selection for increased religiosity to have some negative effect, especially on people’s inclination to question established dogmas.

    (I may someday write a science fiction story with this as a theme. If you’re interested, I suggest visiting my homepage once a year or so. And there are already other stories there, including a couple where you can find traces of this idea.)

    • RS-prime says:

      > Although membership in such sects is a culturally rather than genetically inherited trait, I suspect that people with a genetically influenced propensity to be religious will be less likely to leave such sects

      In other words it /is/ a genetic trait. It’s both. As you imply, most random humans adopted in at birth would leave . . . even most random Whites/Ashkenazim (if one is thinking of Anabaptists, Orthodox Jews etc) adopted in would leave.

      Indeed, that happened with separatist Haredi Jewry early on. Large fractions of their 1950 and their 1900 birth cohorts departed the fold, now it is a few percent of the 1985 cohort that leaves. Kaufmann probably gives numbers on this someplace or other.

      • RS-prime says:

        Excuse me that might not be quite right, I might be conflating certain memories regarding Haredim with stuff about Orthodox Jews in general.

        Suffice to say the general idea is right ; the Orthodox ‘denomination’ — it’s slightly funny, Jews somewhat dislike adopting this term from Christianity but have not been able to displace it — used to lose far more people than it does now.

        You would see the same change over time with the Anabaptists, very likely, it’s just not (much) documented to my knowledge. Not sure how documented it is for the Mormons either.

  5. Sandgroper says:

    asdf – I suspect he’s pulling the leg of a well known and notably not unintelligent chili muncher.

  6. j says:

    Capsaicin deficiency is a suspected cause the skin and eye discoloration syndrome (“WASPing”) followed by infertility and as we know, a special form of brain damage (“Blogging”). Chile con carne cures the condition. Capsaicin is a potent anti-inflammatory, antimutagenic and anticancerigenic agent (Source: วารสารพษวิ ทยาไทย ิ 2551).

    Among the myriad causes cited above, I dare to add “unpredictable environmental changes”. A tribe living a stable and predictable environment like rain forest may be well adapted and any additional IQ is a bother because it may induce its owner to order books by Amazon and to get into debt to attend Harvard. On the other hand, a priestly caste frequently taxed, expropiated, expulsed and forced to re-invent itself in a strange environment will have much use for intelligence.

  7. dave chamberlin says:

    A different explanation with the same outcome to higher intelligence in higher latitudes is less evolutionary pressure by disease. West Africa was justifiably known as the white mans grave up to the 20th century. I’ll bet you are right, there is no single explanation. But there is one cause that very probably exists which we can watch with the most interest because it has the biggest reward if and when the code gets cracked. Because there is such large variation in human intelligence there should be mutations spread through humanity that combine to be small multipliers of G. I’m not holding out any hope that this is happening anytime soon, the complexity of the human brain (10 to the 16th power synapse connections) and with one third of our 30,000 genes expressed in brain function means a whole lot of geniuses tweeking super computers for a whole lot more years before we can even confirm my suspicion. In the meantime we can dream that there will be an upcoming generation where perspective moms and pops will shell out big bucks to have juniors DNA tweaked so that we will no longer need centuries of human misery to push us forward a few steps. Europe was a backwater until we started importing spices, maybe the pepper lovers are on to something.

  8. Abelard Lindsey says:

    I think this suggests that intelligence evolved not to promote thinking, but rather to promote sociability — an ability to understand and communicate with others — and intelligence is a byproduct.

    Or to increase the ability for deception. My current belief is that verbal IQ evolved specifically for the purposes of deception. Much of “sociability” is little more than intentional deception. You will note that language, agriculture, and organized religion emerged at roughly the same time. The purpose of organized religion seems to be for nothing more than the emergence and sustenance of a parasite (e.g. “priest”) class. This alone suggests IQ as for deception.

    • RS-prime says:

      Some scholars assume the development of primitive language-like systems (proto-language) as early as Homo habilis (2.3 million years ago), while others place the development of primitive symbolic communication only with Homo erectus (1.8 million years ago) or Homo heidelbergensis (0.6 million years ago) and the development of language proper with Anatomically Modern Homo sapiens with the Upper Paleolithic revolution less than 100,000 years ago.[29][30]

      <100,000 !~= 10,000

    • RS-prime says:

      But, IQ for deception, ja undoubtably. Including self-deception, possibly even multiple layers of partial self-deception. Trivers is brilliant reading on this, naturally ; so is the blogger Alrenous.

      There’s limited reason to doubt, I think, that deception is a major reason why civilizational complexity appears to be a factor of pop IQ. IMHO Cochran is right to think it multifactorial.

      The fact that you cannot imagine any other purposes for organized religion is truly a riot. Use your imagination. Since you are not dumb it appears you are profoundly obstructed by affective-instinctive hostility toward religion. A kind of self-deception basically.

      • RS-prime says:

        I mean the Grand Canyon wasn’t carved in a day. For deception to exert a selective force upon the pop mean . . . all you need is for the one-sigma smart man to, tactico-strategically, fare at least a couple of percent better than the one-sigma dumb man in their interactions, net of energy expenditure — I mean that’s a dimensionally underdetermined way of putting it, it’s not very proper but you see what I mean. (Energy expenditure may be a wash between the two on average. We have indications that the smart guy’s brain is more efficient in many senses, but on the other hand we also know it is also larger. While brains have shrunk diachronically of late, it seems safe to think that synchronically, for a given time and given pop or locus, the smart persons are larger-brained.)

        And do we observe that this in fact happens — the smart guy winning out for reasons partially tactico-strategic — yes we do. Admittedly, our own industrial civilization is hypercomplex, but we can pretty much observe, and certainly also infer, that this probably held true in the world before 1750.

        The only real ‘danger’ faced by the deception theory — that is, the only point of emphasis that tends toward effacing its level of credibility or salience — is that the smart guy wins out for so many other reasons too. This imposes a certain level of unclarity on our observations, and so forth.

      • The fourth doorman of the apocalypse says:

        The fact that you cannot imagine any other purposes for organized religion is truly a riot. Use your imagination. Since you are not dumb it appears you are profoundly obstructed by affective-instinctive hostility toward religion. A kind of self-deception basically.

        Indeed. The reason that so many actors seem to be members of one crazy religion might be to protect themselves from another group.

    • Andrew says:

      But if the priest class promotes their followers to multiply, they are a benefit, and thus not parasitic.

    • Greying Wanderer says:

      “My current belief is that verbal IQ evolved specifically for the purposes of deception. Much of “sociability” is little more than intentional deception.”

      If you do any kind of group work at a certain level e.g. construction, military etc which are a mixture of say 2/3 manual and 1/3 cognitive which i imagine was the norm when this was being developed then when you hit a snag you get a conflab where the group form a huddle and figure out what to do. One guy comes up with 1/2 a plan, another adds 1/3, a third one adds the final 1/6 and you have a plan. It’s parallel processing. Language allows a group-brain.

      “The purpose of organized religion seems to be for nothing more than the emergence and sustenance of a parasite (e.g. “priest”) class.”

      If the priesthood is benign, higher IQ and promotes adaptive behavior e.g. “cleanliness is next to godliness” or “don’t get divorced” then religiosity can act as a kind of substitute IQ for the dumb.

    • AG says:

      Second that,

      Verbal IQ is really good for salesmanship, which give you more profit, higher recognition, more (including Nobel) awards, good legal outcome (regardless of true responsiblity).

      Have worked with some medical residents who were really mediocre at their medical skill (in term of correct diagnosis, and treatment outcome). But these residents were successful at acquiring all kind of awards like `best resident’, `best scholar’, ect, which looks good on their CV. But be warned, they are really average or even incompetent in their trade as physicians. Best physicians are the one who are more or less like those engineer type.

      So if you are looking for a doctor, you need to look beyound presentation.

  9. nameless37 says:

    Are there really cases where we need to think about ways to lower IQ? As in, groups that have significantly lower values than we expect them to, and indicative of recent degradation? I can’t think of any. As far as I know pygmies don’t score significantly lower than other sub-Saharans or Australians, in the general area that we could call “ancestral IQ levels”. The rest is mostly selection by wealth, with a few kinks (e.g. Ashkenazi).

  10. a very knowing American says:

    There could be two major factors accounting for most geographic variation in g, an accelerator and a brake.

    1. The sociocultural complexity accelerator: Greater sociocultural complexity increases the rewards to g. (This works only if people translate personal success into reproductive success, which is not true in our society, but probably usually true in the past.)

    Human beings depend more than any other animal on learning what they need to know from other members of society. Even in the simplest human society, the rewards to learning from others are so great that it makes sense for people to take a lot of time growing up and put a lot of energy into growing a big brain, compared to any other similar-sized animal. But this also varies across societies: measure sociocultural complexity by number of distinct tool types, or number of distinct occupations, and more complex societies are probably going to give greater rewards to g. The result may be, for example, selection for increased g among civilized folk relative to foragers in similar environments. And increased g in turn probably leads to more rapid evolution of complexity in a positive feedback loop.

    The kind of geographic factors Jared Diamond talks about when comparing the Old World and the New – lots of potential domesticates vs few, a big belt of civilizations vs isolated outcroppings of civilization – let this feedback loop kick in more strongly some places than others. You can imagine a missing chapter in “Guns, Germs, and Steel” on “Yalli’s question and the evolution of g.” Maybe he’ll put this in the next edition.

    2. The X brake (where X correlates with latitude). Something present at low latitudes seems to put a brake on the evolution of g. Maybe it’s heat stress on the brain. Maybe it’s greater mutational load at higher temperatures. Or maybe Rushton was on the right track, and it’s something connected with life history. Infectious disease specifically may be a huge factor (as dave chamberlin notes): add a lot of extrinsic mortality from disease, make it hard to avoid that mortality just by having high g, put pressure on people to accelerate growth and reproduction before they die, and you may reduce the advantage to g.

    A disease brake could account for some variation in g independent of latitude. Tropical forests may be especially unhealthy; African Pygmies look like they’ve got accelerated development, including lopping off their adolescent growth spurts, as well as low g. At the other extreme, some high g populations, including Ashkenazi Jews and high caste Indians, not only occupy specialized economic niches calling for high g, but also have elaborate rules about hygiene. Partly these rules may be superstitions, and partly they may be costly signals of group identity, but they may also reduce disease mortality enough to make high g more affordable.

    In some places, the disease brake may have gotten stronger over time. Up to the modern medical revolution, the world seemed to be gradually adding more and more nasty diseases to the mix. Greece or Mesopotamia – especially the urban areas that attract bright people — might have been unhealthier a few centuries ago than they were a few millennia ago.

  11. Greying Wanderer says:

    “Increasingly, I suspect that there is no single explanation.”

    In a way evolution *ought* to have more than one route to optimal solutions.

  12. kodhambo says:

    There is no cousin marriage in Uttar Pradesh, except among some Muslims; you were thinking of South India, may be?

  13. AG says:

    This research might also support Rushton theory. The trade off between brain and reproduction. But sceptical.

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