June 8, 2013

Breatsfeeding vastly improves brain development in early infancy

Nature vs nurture? Where genetics often fail to explain most differences in cognitive development in a satisfactory manner, environmental causes instead show outstanding importance. 

A very clear case is breastfeeding, which not only provides the best nutrition for babies but also key emotional support. And new research only emphasizes this.


The research found that by age 2, babies who had been breastfed exclusively for at least three months had enhanced development in key parts of the brain compared to children who were fed formula exclusively or who were fed a combination of formula and breastmilk. The extra growth was most pronounced in parts of the brain associated with language, emotional function, and cognition, the research showed.
(...)

The study showed that the exclusively breastfed group had the fastest growth in myelinated white matter of the three groups, with the increase in white matter volume becoming substantial by age 2. The group fed both breastmilk and formula had more growth than the exclusively formula-fed group, but less than the breastmilk-only group.

"We're finding the difference [in white matter growth] is on the order of 20 to 30 percent, comparing the breastfed and the non-breastfed kids," said [lead researcher Sean] Deoni. "I think it's astounding that you could have that much difference so early."

Ref. (pay per view): Sean C.L. Deoni, Douglas C. Dean, Irene Piryatinksy, Jonathan O'Muircheartaigh, Nicole Waskiewicz, Katie Lehman, Michelle Han, Holly Dirks. Breastfeeding and early white matter development: A cross-sectional study. NeuroImage, 2013; DOI: 10.1016/j.neuroimage.2013.05.090

29 comments:

  1. Too bad they didn't also test for cow milk effects. Perhaps that isn't so common these days.

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    1. Cow milk? AFAIK is not too good for babies: very different composition from human milk (that's why formulas exist). Animal milk is food for older kids or adults (also cow milk was less important in the past, goat milk was the most used).

      In the past, when a baby could not be fed by its mother, another woman would usually take the role (or the baby would probably die). It was common among affluent families for example to hire a wet nanny: a woman with a baby of about the same age, who would feed both. The two babies would be later in life "milk siblings", implying certain special sibling-like affinity in spite of their different class, not sure if this term exists in English but it does in Spanish at least.

      Animal milk would be at most a last resource, if no woman was lactating in the community.

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    1. I thought so 20-30% more white mater is a huge difference. I imagine it does not translate directly in terms of IQ but, if it would, it'd be the difference between the average and a bright person who would be admitted in MENSA, or also between the average and a rather limited intellect.

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  3. Maju,

    The problem with research like this - and I haven't paid to see the paper - is that unless you account for confounding factors, like IQ of study participant parents, then the study is fatally flawed.

    I'll use myself as a case in point. I come from a well-to-do family in Ireland, with many high IQ individuals, but was born during the winter of 1963, one of the worst in 150 years and my mother was snowed in much of the last few months. At that time in rural Ireland, fresh vegetables were in short supply, and very few fruits available and no such thing as vitamins.

    I was born 3.5 weeks prematurely, I had very little fat, was suffering from Anemia (due to low iron), was suffering from Ricketts (due to low vitamin D) and had low vitamin C. I was never breast-fed, instead was given a formula called "Oster Milk" for a few months, a product which was banned a few months later. So on paper I should have a severely damaged IQ and prospects in life, right?

    In fact I have IQ 157. For this article to make sense, it would have to mean that I could have had an IQ of 180+, if I had not had such a bad start in life...

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    1. The study does not deal with IQ, just with material stuff: white matter in 2 y.o. toddlers.

      I presume that the authors have cross-checked all possible confounding factors but I have not read the paper either.

      "So on paper I should have a severely damaged IQ and prospects in life, right?"

      Sounds like you had a handicap in your early life, who knows how smart you could be otherwise?

      "In fact I have IQ 157. For this article to make sense, it would have to mean that I could have had an IQ of 180+"

      The article does not deal with IQ. They just found a quite significant white matter difference. They do not seem to have reported gray matter difference, nor astrocyte variation, etc.

      Of course we can easily assume that a difference in white matter affects IQ or intelligence in general (maybe other aspects of intelligence like EQ or whatever) but we do not know it and we cannot extrapolate it, much less linearly.

      And I don't care if you have got a 157 score in an IQ test: if you can't discern between white matter and IQ, etc., you are not demonstrating your allegedly outstanding intelligence but rather reasoning at the level of IQ=80 or whatever.

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  4. Maju,

    But the article as quoted makes the usual socialist claim that:
    Poverty --> lower cognitive development

    Whereas in fact most evidence point to the opposite causality:
    Lower cognitive development --> poverty

    The volume of "Grey Matter" is usually correlated positively with IQ, but let's not forget that among White populations, the group with the highest reported IQ are Ashkenazi Jews, and they have a greater volume of "White Matter" relative to "Grey Matter" than other White populations - therefore White matter likely an important for higher IQ also.

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    1. But the article as quoted makes the usual socialist claim that:
      Poverty --> lower cognitive development
      .

      Not at all: the article "as quoted" is very objective and only establishes a clear correlation between some breastfeeding and brain development, expressed as "white matter" in "key parts of the brain".

      You need some money to buy formula, so hardly there can be any apparent correlation between formula feeding (a modern urban costly fashion) and poverty.

      Said that, I would agree that nutritional and emotional deficiencies in early childhood (and fetal development) most probably damage the brain, even dramatically so. There are other entries in this blog supportive of a clear correlation between emotional trauma and much smaller brains, an even more clear case of environmental influence, but again not obviously related to economical status, because you can perfectly be rich and scare your babies to death and be poor and give them all the love.

      It is very possible that very poor people have nutritional deficiencies that affect their children's brain (and other) development in a negative manner but this article does not say that.

      Whereas in fact most evidence point to the opposite causality:
      Lower cognitive development --> poverty


      There is nothing that actually supports that claim. You should apply your suggestion of "accounting for confounding factors" because all what I have seen in that sense is nothing but pathetically manipulated Nazi propaganda (Lynn, right?)

      Every single person supporting that farcical "study" is a Nazi. The study itself is funded by the Klu Klux Klan. And the figures managed in it are absolutely unbelievable. If I make you to answer an IQ test in Yoruba... you'd score very low, no matter your actual intelligence. Same if you make Yoruba children to answer such a test in English. Never mind cultural biases etc.

      One interesting element that really calls for a confounding element being the cultural extension of literacy is that in Lynn's data the Sinosphere stands as "most intelligent" on Earth, however how is genetically different a Cantonese from a Vietnamese? In nothing relevant! But, lo, miraculously they score very differently, what clearly indicates, in my understanding that literacy skills, learned in the general cultural surroundings and also in school matter a lot, because Cantonese use the Chinese script but Vietnamese use a much more simple alphabet.

      If I am correct in this, and I probably am, cultural elements confound IQ tests a lot and therefore these are only comparable, if at all, within the same culture. IF cultural elements, such as literacy and scripts, are so influential, I am very inclined to be skeptic of IQ (as we know it) as reliable measure of intelligence.

      Another possible source of your claim are studies that measure IQ within professional categories. These do show a quite clear differences between average and median IQ in each category. However the higher range is almost always the same (quite above 130), even for the worst paid professions. So the difference is only or mostly in the lower range, because the requirements of some careers obviously pose a barrier for less intelligent people to reach certain professional qualifications, which are in themselves an intellectual challenge. As in general these high IQ professions are better paid, there is a correlation between IQ and income - but would all be paid the same, there would not probably be such correlation (logically).

      What was first the chicken or the egg? Where is the cause here? Highly debatable.


      ...

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    2. ...

      "The volume of "Grey Matter" is usually correlated positively with IQ, but let's not forget that among White populations, the group with the highest reported IQ are Ashkenazi Jews, and they have a greater volume of "White Matter" relative to "Grey Matter" than other White populations - therefore White matter likely an important for higher IQ also".

      All this you say is new for me (except gray matter correlation with IQ). Anyhow I do not believe that Jews are (on average) genetically smarter but culturally so, as happens with all communities when compared (always in relation to an idealized standard). I am of the opinion that cultural elements weight a lot in IQ tests. I have done myself some and never found them neutral at all: they do not measure your wits but your capacity of agreement with certain cultural assumptions, at least in great part, including your fluidity and vocabulary in the language in which the test is made and mathematical skills, all them learned skills, not innate.

      So IQ tests can compare the intellectual skills (which to some extent imply intelligence) of children or adults with similar education and societal values but it gets very hard to compare across cultural borders. It may simply not be possible at all.

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    3. Maju,

      I'm no fan of Lynn and have criticized his methods repeatedly. The thing is though that his result was largely correct, but he didn't have to fabricate data to make it so. He also tends to pick winners and losers in terms of countries and boosts his favorites IQ a few points and subtracts a few points from his least favorites. See for instance Holland, Germany, versus Ireland, France.

      In terms of brains, Grey Matter is basically Neurons, whereas White Matter is mostly the connections (dendrites) between those neurons. In the absence of enough fatty acids I could imagine that dendrites, who are insulated with myelin - a fat coating - could be somewhat compromised.

      Some conditions like Autism - resulting from explosive growth of grey matter a few months after birth - leave the individual with much more grey matter than white matter.
      It's also been shown that those with more White Matter are better at deception and guile.

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    4. Lynn, besides manipulating the raw data in the ways you say, used highly unreliable and/or not comparable data also (what is another type of manipulation). Besides his "study" I don't know of any other global intelligence comparison of any sort, so it beats me how can your reach to the conclusion that "his result was largely correct". No it is not correct: it's a blunt manipulation with the worst motivations and the less acceptable results ever.

      "In terms of brains, Grey Matter is basically Neurons, whereas White Matter is mostly the connections (dendrites) between those neurons".

      I know. Probably both weight in actual intelligence, along with other less obvious factors, the same that there are several factors adding up in computer performance and it's not just CPU but also RAM, swap memory, hard disk speed and organization, and then of course the programs installed and used, as well as the user him/herself (etc.) In the brain it is probably even much more complex: the computer is always just an analogy.

      "In the absence of enough fatty acids I could imagine that dendrites, who are insulated with myelin - a fat coating - could be somewhat compromised".

      That actually affects brain performance but mostly as degenerative neuronal illnesses: http://en.wikipedia.org/wiki/Myelin#Disorders_of_the_myelin_sheath

      The most common disorder caused by myelin damage is multiple sclerosis, being also involved in schizophrenia, it seems.

      A more interesting aspect of white matter density in direct possible relation with intelligence is IMO that it implies more connections. We are not even able to discern what these connections do case by case (more does not always imply better) but let's assume that on average more white matter implies more internal connections and therefore a better internally communicated brain (our "intranet" of sorts). That way mere increased connectivity may help with intelligence in general and particular aspects of it, regardless of gray matter.

      "Some conditions like Autism - resulting from explosive growth of grey matter a few months after birth - leave the individual with much more grey matter than white matter".

      Interesting. I was not aware of that.

      "It's also been shown that those with more White Matter are better at deception and guile."

      Interesting as well.

      I imagine that while, in general gray matter adds to raw processing capacity, white matter provides the flexibility and speed. That's maybe why autistic people tend to get immersed in almost exclusively a single attention focus (usually not communicating with others), not necessarily a bad trait if not so exaggerated, while the "white matter people" you mention would be more flexible, quick-witted, what may be used to the purposes you mention but not necessarily so.

      Breastfeeding is then good to counter autistic tendencies? I can't say for sure but it would fit with what you say.

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  5. all what I have seen in that sense is nothing but pathetically manipulated Nazi propaganda (Lynn, right?)

    A bit surprising, that you haven't heard of Herrnstein and Murray (of The Bell Curve fame), Levin, Cronbach and literally hundreds of studies on the subject. Incidentally, they are discussing Gould at Dienekes´, possibly the most prominent critic of both Murray's and Levin's work. Of course, these matters are controversial, especially when the slippery race factor is included, but the relationship and causation sense is pretty mainstream in psichology. And it doesn't seem to require a lot of work to gather support for the idea that IQ levels are a good predictor of social and economic achievement. http://en.wikipedia.org/wiki/Mainstream_Science_on_Intelligence http://en.wikipedia.org/wiki/The_Bell_Curve#APA_task_force_report

    If I make you to answer an IQ test in Yoruba... you'd score very low, no matter your actual intelligence.

    This kind of objections have been discussed ad-nauseam. Measurement of IQ in children of age 2-3 is common place. I recently saw one published in Chile. I believe it was Cronbach who devised the concept of "g", whch has been used to avoid using the term intelligence and focus tests on innate mental abilities. For example, there's little room for cultural/environmental factors when remembering a sequence of familiar images or numbers in reverse order.

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    1. I'm vaguely familiar with that extremist rubbish you mention and saddened for such kind of ideologically motivated pseudoscientists being so influential in pop culture, it seems.

      Let's see: Murray is first of all defined as "Libertarian", what in the USA means ultra-capitalist fascist (nothing to do with freedom nor democracy, just with social-darwinism, which in turn has nothing to do with Darwin). He is not psychologist but political scientist and confessed social-darwinist, who works for the ultra-capitalist think-tank American Enterprise Institute, with continuous presence in the most dubious forums like the Bilderberg Group and the Tea Party. His opinions therefore are not likely to be neutral nor scientifically informative.

      Hernstein was indeed a psychologist but a very old-school one ("Skinnerian", go figure!). In any case he's dead, so he cannot correct his errors. Let him rest in peace or whatever.

      Gottfredson herself does not seem very neutral either and her stand on "race and intelligence" is outragingly racist.

      It is interesting that you do not seem interested in the many and demolishing criticisms that Gottfredson's article got, including some who think that even g itself is not clearly inheritable. The problem here is that there is one camp (the racist and sexist reactionary right), which is continuously making propaganda of some of these authors while ignoring the others, while the "opposition", so to say, those who are highly skeptical of those claims, often remain less vocal, because in truth there is not too much to say about intelligence without showing how little we know.

      "I believe it was Cronbach who devised the concept of "g", whch has been used to avoid using the term intelligence and focus tests on innate mental abilities. For example, there's little room for cultural/environmental factors when remembering a sequence of familiar images or numbers in reverse order".

      It was not Crohnbach, who incidentally refused to sign Gottfredson's article, as did at least several other high profile figures in IQ studies. g has been studied since Spearman (eartly 20th century), who described it as the statistical convergence in performance of individuals across different sectoral tests and is not too different from generic IQ, if measured properly with a complete battery of tests (not too common). The most modern revision of Spearman's theory of g, which is the Cattell-Horn-Carroll model, has been widely introduced in standard IQ tests since the late 1990s (but as you see it is something very recent and impossible to compare, as Lynn does mischievously, with 1950's colonial IQ tests to Tswana children in English, for example).

      It is interesting anyhow that, while "tests of g are the best single predictors of job performance" (but only 0.55 correlation coefficient!), "the association between job prestige and g is lower" than when we only measure standard IQ. So, assuming that g is actually a good, or at least quite decent, measure of "pure" intelligence, it seems that it affects much more job performance (efficiency, capability) than career achievement (wealth and prestige), rather throwing some cold water to the claims that intelligence, especially inherited intelligence (best correlated with g), is the main cause of socio-economic achievement.

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    2. Glad to see that you've brought yourself up to date on this matter so quickly. To the point of being able to clearly determine who's right and outrageously wrong, it seems.

      Perhaps some of the scholars involved in these studies are not as ideologically unbiased as yourself. But the extremist rubbish produced by ideologically motivated pseudoscientists that I mentioned is what the American Psychological Association concluded. To quote:

      - IQ scores have high predictive validity for individual differences in school achievement.
      - IQ scores have predictive validity for adult occupational status, even when variables such as education and family background have been statistically controlled.
      - There is little evidence to show that childhood diet influences intelligence except in cases of severe malnutrition.

      The idea that such a large number of psychologists and their own elected representatives are Nazis seems a little far-fecthed to me.

      Yep, what Cronbach actually created was the G-theory and, indeed, Lynn has been rightly criticized for the methodology used in that unrelated paper that (I don't know why) you keep mentioning. But I don't understand how such a simple notion can be so vehemently rejected. People with higher IQs, on average, do better at school and later on in their professional careers. That's what the APA and most anybody interested in education concludes, with the reverse being also true, of course.

      As for the somewhat related "taboo debate", the APA concluded that "At present, no one knows what causes this differential." In those circumstances, I guess the best one can do is ponder the evidence presented for each case and try to apply good judgement by oneself.

      To be honest, in all these matters I used to argue along your same lines about a decade ago. But when presented with new empirical data that contradicts my prior beliefs, I feel forced to change my mind. I don't know what you do in that scenario.

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    3. Not sure where you took your quotes from but "predictive" only means that there is some statistically significant correlation, nothing else. Nobody denies that there is some correlation between IQ scores, for whatever degree and aspects that they are able to measure of all intelligence, and other real life results but we can't deal with this relative and statistical correlation as if it was a 1:1, a 100% correlation: it is not. Also statistical significance may be less significant than we are led to think: http://www.sciencenews.org/view/feature/id/57091/description/Odds_Are_Its_Wrong

      "I don't know what you do in that scenario".

      Normally I first look for all the ways that such "empirical data" may be wrong (which are usually way too many). Only if the data is actually "empirical" and independently replicated by trustworthy researchers, especially multiple times and looking for all possible confounding factors, I will accept it.

      What I say is that the likelihood of mistaking the effects and more so the causality behind these effects in these issues is extremely high and therefore must be treated with the most delicate and exquisite gloves, because the implications are immense.

      For example, let's assume that in fact African-Americans have an innate lower average IQ (what IMO has yet to be demonstrated). I will assume by the moment that it is also inheritable. If so, it is very possible that it is the product of selective slave breeding in the plantation system favoring the less smart individuals and massacring the brightest ones, which could tend to be more rebellious and independent (yes, there is also a positive correlation between intelligence and leftism/rebelliousness and a negative one with conservatism and resignation/submission). I say because for example I know for a fact that Caribbean Afroamericans succeed much much more often in US society than US-born Afroamericans, demonstrating that it is not a racial matter, at least not in the broadest sense of globally defined "races".

      However I have made a lot of assumptions to reach to that point and therefore it can be that the reasons are not (or mostly not) genetic but maybe cultural (Caribbean and US-born AAs have different cultural backgrounds, being the former used to be the majority in their countries and not or very limitedly subordinated to white power).

      There can be many other confounding factors that I have ignored in the successive assumptions I had to make to reach to your point of interest and insistence. The matter is clear as mud in fact but I seriously doubt that it is "racial" (genetic) at least in the broadest global level because after all African diversity essentially includes most (if not strictly all) non-African variance.

      I have accumulating and very legitimate caveats and strong suspicions on all the process carried on in order to reach such deeply controversial and ideologically loaded "conclusions". The confounding factors are way too many and the statistical significance rather low.

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    4. The APA conclusions come directly from the link I posted earlier: http://en.wikipedia.org/wiki/The_Bell_Curve#APA_task_force_report The fact that they reached these conclusions reveals that a large volume of literature exists on this matter and that it has been extensively reviewed, especially considering the controversial nature of the subject. I have read some of it and it definitely takes more than a cursory examination of Wikipedia entries to start grasping the subject. The huge list of references in the report itself should be a good start: http://www.gifted.uconn.edu/siegle/research/Correlation/Intelligence.pdf

      That said, I am aware of the limitations of social science studies and the statistical analysis applied in them. An even more thought-provoking debate appeared very recently in the press and statistical blogs. I'm still getting my head around it: http://wmbriggs.com/blog/?p=8295 But, really, what we are dealing with here is a trivial proposition: "smarter people do better at class and at work". Or, put differently, "whatever it is that IQ tests measure, its magnitude is positively correlated with educational and social achievements, when controlled for other factors". The ancillary assumptions that this magnitude is highly hereditary and thus changes little over time stem from the literature mentioned above.

      Going back to the start of this thread, a second, different debate is what this all implies, if anything, for different racial groups. Perhaps you are right that it means nothing. But I think that the first step that one should take before analyzing the evidence dispassionately is ask oneself the following: if evolution has resulted in obvious average phenotypic values among human races, what biological constraint could exist that would prevent the existence of similar differences at the brain organ level?

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    5. Pretty appropriate and funny the article (and some of the comments) on statistical significance you link to.

      As for the APA conclusions, they may be OK but are from almost two decades ago. For example: "There is little evidence to show that childhood diet influences intelligence except in cases of severe malnutrition" doesn't mean that there is no evidence whatsoever or that future research will not find it. Rather than a beaten dead horse, it is a wide area of mist of which we know little as of 1996 and even as of now. New evidence in this sense (not just nutrition but, maybe more importantly, emotional neglect) is being fond at slow pace.

      Also, while the genetic influence on intelligence remains highly elusive (see here and here), other factors like epigenetics (which in some cases may also be heritable across some generations but mostly responds to environmental influences) seem to have also their share in it. All this (and surely much more that I ignore) is indeed from after the APA spoke their mind in 1996.

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    6. ...

      "But I think that the first step that one should take before analyzing the evidence dispassionately is ask oneself the following: if evolution has resulted in obvious average phenotypic values among human races, what biological constraint could exist that would prevent the existence of similar differences at the brain organ level?"

      This has a quite easy answer: the phenotype (and their genetic causes') differences between human "races" (I'm not too keen of the term because even my fascist grandpa, who was a psychiatrist, claimed that "human races do not exist, only ethnicities") or rather larger population clusters are of two types:

      1. Most of them are trivial and therefore stochastic, caused by founder effect and drift, exactly the same that you resemble (or most do) your parents and other relatives. It has no or extremely low adaptive value, unlike intelligence. Considering that most Europeans, for example, share many recent (and ancient) ancestors with any other European, the result is obvious: they tend to look alike.

      2. The most apparent one, skin color, is caused instead by a very important adaption. You may be familiar with it because it is a classic in the basics: humans photosynthesize vitamin D in our skin and food sources of this vitamin are very limited (essentially fish). Vitamin D is essential for bone formation but, crucially, it has been found in the last years that it is also very important in brain formation and that lack of vitamin D in childhood is very dangerous for the mind (this could well be a confounding factor in race-oriented studies of intelligence). Vitamin D has other very critical roles in human biology, hence skin-color adaption is very important, see category vitamin D in this blog and its predecessor.

      So it is hard to imagine why would evolution push in favor of reduced intelligence. The only such pressure I can imagine is civilization (=human domestication) having some of that effect, just as it does in other domestic animals when compared with their wild relatives. This could explain why paleolithic humans appear to have been in almost all cases within the top segment of current variation for brain size. If so, then the most civilized peoples, or maybe those with oldest civilizations, should be the less intelligent on average - but as of now this is just an unsupported hypothesis, barely a wild conjecture, which won't probably stand.

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    7. Let's put this differently. Whether through genetic drift or evolution, different "human clusters" have ended up showing a large number of different physical traits: average height, average strength and body mass (and you don't need evolution to push for reduced strenght to get this empirical outcome), lenght/size of certain muscles and organs, prevalence of certain illnesses, tolerance to certain foods/substances and literally hundreds of similar phenotypic attributes.

      Given the above, the question remains: is there any plausible biological mechanism that would prevent any difference whatsoever from appearing in the average (and standard deviation) of brain-level structures in different human clusters?

      It may also be helpful to follow up on your wild animal comparison. Just like Asian elephants ended up being smaller than their African counterparts, it seems that their behavioral traits also evolved differently, the former being less docile. Likewise, North American cougar attacks to humans are regularly reported but no record exists of their South American relatives ever attacking humans. It doesn't look like any such biological constraint is present on the brains of non-human species.

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    8. Physically most healthy humans of similar age are very similar. Olympic champions are not that outstanding in relation to common people, the main differences being across gender in fact. Between populations the differences are much less notable in fact, with some peculiar exceptions such as Pygmies' short size, which might be an adaption of some sort to forest conditions (such as using animal-made tracks or even climbing itself, mineral scarcity has also been suggested as a possible cause). There does not seem to be much evolutionary pressure on such traits (probably because our main adaptive advantage is intelligent adaption: wits rather than brawn).

      There should be some evolutionary pressure in favor of intelligence and this is evident in the long run (Homo genus' evolution). However the "races" of humankind are not older than 100-50 Ka, while the evolution in Homo sp. took about two million years. Also it was not merely gradual but appears to have suffered of punctuated equilibrium dynamics, the last of which was the appearance of our species H. sapiens c. 200,000 years ago.

      As you may know, in punctuated equilibrium theory, which is more often right than not, things tend to remain stable (with some diversity and gradation) between crisis, when evolutionary change speeds up. In my understanding there has not been any such decisive crisis since the coalescence of our species c. 200 Ka ago, so our species has remained basically stable, with just lesser changes, most of them of limited functional relevance.

      In any case, the chances are that, would there be any such decisive pressure, populations with the greatest diversity would adapt much more readily because they do have much more to choose from. In humankind, sapiens and archaic alike, this means Africa as number one candidate by far to hold the necessary diversity for most adaptive challenges. It happened in the past at least twice in fact.

      While evolution is indeed driven often by founder effects, these reduce diversity quite dramatically and their effects are much more often than not tainted with some negative repercusions. It has been demonstrated once and again, for exmample, that non-Africans carry many many more deleterious (anti-adaptive) mutations than Africans and these are much more common among us. New diversity will build up eventually but it needs lots of time on its own, as well as large populations, so among the OoA populations this is still an ongoing process and, unless some sort of catastrophic bottleneck happened in Africa, we are not likely to ever reach their levels of diversity unless there is widespread intercontinental admixture first.

      "... elephants"...

      Elephants are several species, even genera, so they are not really comparable to Homo sapiens in terms of biological differentiation.

      "... cougar"...

      Not privy to the particulars but I imagine this depends on other factors than mere "evolution", possibly to different actual type of interaction, availability of wild land, etc. But honestly, I do not know.

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    9. That's all fine. But everybody knows (especially sports fans) that people from West African descent are faster and more muscular than Europeans, for example. Or that Northen Europeans and Caucasians in general are taller than East Asians. Likewise, we know that testosterone levels (which have an effect on certain brain functions) also differ between races: e.g. http://www.ncbi.nlm.nih.gov/pubmed/1621259 And so on. How these differences arose can in most cases be nothing but especulation. But we know that they are there. Can nature allow these intra-species physiological differences to develop but somehow prevent any intra-species differentiation in anything that could affect intelligence? If not, we are very likely to find different average intelligence values among ethnic groups.

      By the way, studying possible racial differences is *not* racism. As Murray has argued, the information obtained from such studies could very well be used by policymakers to give extra support to groups known to have any disadvantage.

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    10. So how do you make those small physical differences, which seem pretty much derived from the OoA bottlenecks with some later remixes, be "caused" by adaptive pressure. Is it because Africans have to run from lions or something? (joke of course).

      Incidentally there are also small and weak Africans, just that, probably, because their genetic pools are more varied so there's more to choose from.

      "testosterone levels (which have an effect on certain brain functions) also differ between races"...

      Not sure if correct because it has a paywall and in any case it is not a study about global "races" but about US ones, which are not necessarily representative, much less "pure".

      "Can nature allow these intra-species physiological differences to develop"...?

      Nature generally tends to keep all not obviously awful diversity because dynamic equilibrium works best in a reality of changing conditions. So, unless bottlenecks happen, they balance each other along time: sometimes A is better, sometimes B works best and A is a handicap instead, etc.

      "... but somehow prevent any intra-species differentiation in anything that could affect intelligence?"

      Actually there is also diversity in intellectual capacity and skills, at least at individual level. What I wonder is, if all is a single parameter, as the kind of simplified discourse you favor ("IQ", "g", etc.) and not actually many, why Nature is allowing the "retards" and even the "mediocre" to survive at all. This of course regardless of "race".

      And also, if I am correct, and most of what you say is just (or mostly) punctual expression of a wider, more diverse, gene pool, why wouldn't Africans also be more intelligent?

      Many questions, no really good answers at our current state of knowledge because, as things stand, I do not even know if the average youths of Nairobi are actually faster than the average youths of Berlin, for example. Has anyone even bothered measuring that? All we know is about a few chosen ones, the elite of the elite, and even among them there is quite a diversity of colors, of "races".

      "By the way, studying possible racial differences is *not* racism."

      Defending them on very poor evidence and not wanting to look at the supposed "evidence" critically is clearly a major symptom of a racist mind.

      I'm not against of research of any kind, I am against biased research and especially upholding very doubtful conclusions that are clearly supportive of racist policies and ideas without even bothering to double check the facts.

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    11. Actually there is also diversity in intellectual capacity and skills

      Precisely. There you are. And it's true that I'm basically interested in what has been empirically measured. Discussing unmeasured or unmeasurable values is probably not worth spending much time on.

      I do not even know if the average youths of Nairobi are actually faster than the average youths of Berlin

      I guess I could pile on on this but unfortunately I don't have the time for that. East Asians have slanted eyes and tend to be brachycephalic. Period. Different human races, clusters or whatever exhibit different physical traits. Period. Some of them have been systematically measured. Some others not so much but anyone can see them at first sight.

      Regarding biased research, it is important to note that the possible existence of such bias is not evidence in favor of the hypothesis that contradicts the one that is being posited. Even if you managed to find some bias or error in every single one of the hundreds of papers mentioning race differences, you would still have to produce your own evidence in favor of your hypothesis. Namely, that there are no differences whatsoever between races/ethnicities in anything related to the brain organ.

      As a matter of fact, different testosterone levels among races seems to be the common wisdom in medical research but there is some conflicting evidence. What nobody in that community discusses is the possible existence of such differences. Precisely my point.
      http://cebp.aacrjournals.org/content/18/5/1484.full
      http://jcem.endojournals.org/content/91/11/4326.full

      It was only last Friday that I gave blood for a child of a different race. She’s in need of urgent surgery and blood donors were requested. But I wouldn’t dare to say that I don’t have any racist feelings. In fact, I don’t think I’ve ever met any single person of any origin in my life who didn’t have such feelings to some degree. I believe this is just part of the human nature. However, I have spent about 15 years following on and off the IQ debate and I’m totally convinced that the political correction bias is way stronger than the racist bias. After all, the concept of so many White Supremacist scholars defending the notion of Asians and Ashkenazi Jews being more intelligent on average than Whites is a strange one.

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    12. "Even if you managed to find some bias or error in every single one of the hundreds of papers mentioning race differences, you would still have to produce your own evidence in favor of your hypothesis".

      I have not seen a single such reference in THIS discussion or, wait, one affecting only US subpopulations, which, as I said, probably do not represent well or at all global macro-populations (aka "races").

      I don't have to produce any evidence in favor of a non-hypothesis I do not have: absolute equality is the null hypothesis.

      I have posited one piece of evidence here that nobody ever could question: the San (claimed by Lynn to have some 50 IQ, i.e. total retards, probably unable to even feed themselves) actually can solve extremely complex information puzzles that most or all white or any other non-HG people can (probably not even highly trained nature guards). That is an (non-numerical) kind of IQ test and the results are very blatant: in that kind of intellectual skills, which obviously imply highly complex inferences, they are outstandingly much much better, surely because they trained at that from childhood.

      That is evidence: positive evidence of high (or at the very least normal) IQ among the San or Bushmen and negative evidence about the most famous or rather infamous racial differences' theory.

      This is not just ranting: it is objective data.

      "... there is some conflicting evidence"...

      Typical.

      "... I’m totally convinced that the political correction bias is way stronger than the racist bias".

      Your conviction, not mine at all. One thing is clear there seems to be some correlation between those obsessed with "the mismeasure of mind" and those obsessed with "the mismeasure of man". They also seem to be conservative (don't blame them: it's a neurological condition), conservatives seem to be dumber on average (even Razib admits to that), racists are dumber on average and people who believe in "God" are dumber on average...

      Why should I trust the "dumb" and paranoia-prone conservatives, racists and religious folk, are you kidding? I'm admittedly "racist" in my own way: "racist" towards reactionaries. I truly can't stand them and the failure they bring to our Human species.

      But I doubt it's a simple genetic problem: otherwise I'd also be in favor of eugenics. The problem is at least largely environmental. At least I think so. Hence changing the environment, will change Humankind for the better. Yet the main environmental factor is Humankind itself, and that is a drag: an ouroboros kind of problem, that guess can only be solved in a cyclical spiral manner: dialectics.

      Sadly I don't have that much patience.

      ...

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    13. ...

      "... the concept of so many White Supremacist scholars defending the notion of Asians and Ashkenazi Jews being more intelligent on average than Whites is a strange one".

      Not at all: Asians do not matter almost in the US racism dynamics while Jews (particularly Ashkenazim) are a very privileged community and today, as in the past, many fascists are in favor of this privilege and very particularly of Zionism (a most outstanding example is the Utöya butcher who was adamant in favor of a pro-semitic, and pro-Zionist, but islamophobic, new form of Nazism - but there are many others like him who hide under sheep clothes, very especially in the Anglosaxon World, where there was never any strong antisemitism).

      Racism today as in the past is only meant to justify the privileges of the powerful and the subjugation of the oppressed.

      Whatever the case I find very notable in such pseudoscientific, total junk, "studies" that they can "find" alleged "genetic" differences between nearly identical populations such as China and Indochina peoples. This is in my understanding a clear case of confounding environmental factors, such as the writing system (learning the highly complex Chinese script must really train the brain).

      Anyhow, as I said before, I do not have much patience for the kind of not-so-subtle pseudoscientific racist junk that you are pooping here. So please, quit it.

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    14. I have given a number of links with lots of further references therein that address the issues at stake from different perspectives. Unfortunately that's all I can do. I cannot read them for you. Much less so with a mindset free of ideological prejudices. And besides I also don't have any apostolical inclination. Much more interesting would have been to learn why I (and a majority of American psychologists, according to a recent poll) are wrong. But that possibility is obviously exhausted.

      absolute equality is the null hypothesis.

      Yes, in a world full of Nazi, Zionist and Fascist conspirators that must be true, I guess. In my world the null is what you are trying to test evidence against, whatever that may be.

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    15. You have provided several links: two to already debated Wikipedia articles, one to a pay-per-view study that I doubt you have read yourself and lastly two to the quite unrelated issue of hormones. I fail o see how they address the "issues at stake", as you call the issue of alleged racial inequality in intelligence.

      I have also provided several links that are much more directly related, showing that (1) only 2% of genes detected so far seem to have any influence on intelligence, that (2) epigenetic differences instead have dramatic differences on intelligence (twin study), that (3) emotional trauma causes brutal brain shrinkage, that (4) vitamin D levels (possibly affecting dark skinned people in high latitudes) seriously affect brain development in childhood and (5) that the emotional-nutritional environment of breastfeeding clearly affects a key component of the brain: white matter (this entry).

      I bet you haven't read, much less meditated on any of them.

      You are claiming bad science on mere vague appeals to mysterious authority or crowd pull. I am providing empirical facts instead.

      Take a break, please.

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  6. Maju wrote,

    "So it is hard to imagine why would evolution push in favor of reduced intelligence. The only such pressure I can imagine is civilization (=human domestication) having some of that effect, just as it does in other domestic animals when compared with their wild relatives. This could explain why paleolithic humans appear to have been in almost all cases within the top segment of current variation for brain size. If so, then the most civilized peoples, or maybe those with oldest civilizations, should be the less intelligent on average - but as of now this is just an unsupported hypothesis, barely a wild conjecture, which won't probably stand."

    The problem with this hypothesis (that the Neolithic revolution equates to human self-domestication, which has led to decreased brain volume of present-day humans relative to Palaeolithic humans) is that present-day and recent human populations who have practiced cultures most similar to those of Palaeolithic humans are not the unparalleled founts of genius that we should expect them to be.

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    Replies
    1. We could think of several confounding factors like: (1) survivor HG populations have been pushed to the edge and are suffering from other problems for that reason like inbreeding or whatever, or (2) we are not using the right intelligence tests like the kind of stuff they do very well and almost every single civilized person can't at all, such as correctly interpreting the action of animals with extreme detail from mere tracks.

      But whatever, I was just outlining what I described myself as a "wild conjecture", so I really do not wish to insist too much on it.

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