Why do IQs vary across nations?

People who live in countries where disease is rife may have lower IQs because they have to divert energy away from brain development to fight infections, scientists in the US claim.

The controversial idea might help explain why national IQ scores differ around the world, and are lower in some warmer countries where debilitating parasites such as malaria are widespread, they say.

Researchers behind the theory claim the impact of disease on IQ scores has been under-appreciated, and believe it ranks alongside education and wealth as a major factor that influences cognitive ability.

The full story is here.  The original research paper is here.  I'm not sure the authors have a very good test against alternative hypotheses, but still a correlation remains after making some appropriate adjustments.


This cannot be true. For many decades, India has been one of the most disease prone nations. Yet it has produced some of the world's leading scientists, researchers and software programming professionals. I can elaborate but I guess you got the drift.

The Lynn & Vanhanen data that they use is extremely suspect particularly for Sub-Saharan African. It has been heavily criticized by numerous authors. For quite a few of these countries the average IQ, in this data, ie below 70- which is the threshhold for mental retardation. Do you really believe that?
So there are simpler explanations for the correlation: poor countries have lousy data & also have lots of parasites. Its also hotter there. Its also closer to the Rift Valley. The people are more black.
You can think of lots of ideas that "explain" this correlation and generate psuedo-scientific papers - as quite a few authors have.

"For quite a few of these countries the average IQ, in this data, ie below 70- which is the threshhold for mental retardation."

Well, it is consistent with lack of scientific and high-tech output from said countries...

It is also consistent with the Flynn Effect observed through the last 100+ years. Peasant Euro populations of the 19th century would probably score only a little above 70. Lack of iodine, bad nutrition etc. can definitely create a a big population of near-retards, just like specific diseases can create a big population of deaf people etc. (Ever heard of the Bedouin tribes in Negev? Some of them have over 50% deaf people, result of long-running inbreeding).

In fact, a remote Czech (Moravian) location of Bílé Karpaty in the 1870 was a favorite study place for physicians, who observed high frequency of cretinism there. Reason: serious want of iodine in food. There were complete villages full of retards there.

Of course, they were white, so it is not a taboo topic. Today, suggesting that Africa suffers from lower IQ values will automatically brand you a suspect KKK member, regardless of truth.

Almost forgot to take my daily iodine pill. Thanks for reminder, Marian.

not_scottbot: "whole groups of people are demonstrably beneath other groups"

Well, that assumption only makes sense if you expect intelligence to be a gauge according to which individuals or groups are sorted. What if not? What if you're interested just in the facts and do not have people-sorting agenda?

I can perfectly accept that, say, Czechs are "beneath" Kenyans when it comes to sprint and that Italians are "beneath" Finns when it comes to surviving long, sunless winters. But that does not mean that I should spit on the Italians or that I hate them, right?

Why is intelligence such an exception? Do really most people intuitively rank others by intelligence?

I've been wondering, are the only distinguishing features of race which box you check on the census and the degree to which you suffer from racism, and skin color?

Anyway, rather than getting bogged down in who may be ignoring reality due to racism versus non-racism I wonder if there is a nutritious anti-microbial diet.

By the way, from the article: "Thornhill believes that nations who have lived with diseases for long periods may have adapted, by developing better immune systems at the expense of brain function." Sounds like genes to me... so sorry, not_scottbot. Sounds like the human phenotypes in warmer, more disease-prone areas developed differently than other phenotypes. (shocking, I know)

The "whole concept of IQ" is "to put it mildly" strongly correlated with success in manifold areas of life and universally accepted as a useful measure by serious scientists.

Garbage. IQ is strongly correlated with success, but you need to do much better than that. Correlation with success does not mean that IQ is a measure of innate intelligence.

It could just as easily be a measure of quality of development - were you read to as a kid, did you receive appropriate childhood nutrition, were you abused, etc. We know these things matter.

IQ also correlates really well with "trying your hardest on an IQ test", which is driven by all kinds of factors including how one is socialized to respond to written tests. These socialization factors could drive both IQ and lifetime success.

For reference, a few other things strongly correlated with lifetime success that are not measures of innate intelligence:
- Going to college
- Having a Y chromosome
- Having parents who own a Bentley or Rolls Royce
- Going to private school
- Amount of crack your parents smoke (inverse)


I am reminded of a Terry Pratchett quote. Let me google; hmm, not finding quite the version I remember, but (piecing from the snippets I find) it went something like:

"Some people think they are civilized because they know what a pronoun is, or how to find the square root of 27.4. This is in contrast to backward and ignorant people, who only know childish and useless things like which of the 70 almost identical looking species of the purple sea snake are the deadly ones, how to navigate across 1000 miles of featureless ocean by means of a piece of string and a small clay model of your grandfather, how to extract a nutritious mush from the deadly root of the sago plant, and other such trivial matters. Oddly, when people become civilized, everyone knows about the pronoun but almost no-one remembers the sago root."

Which is about as good a summary of the basic problem with IQ testing as I have ever read.

High IQ allows you to build machines to traverse the oceans, look up information on any plant or animal, and kill any dangerous critter pretty much at will from orbit.

You stick to your noble savages, the rest of us (who enjoy air conditioning, running water, sanitation, etc.) will go with the high IQ.

IQ scores are basically a measure the extent to which people are entrained into Western Culture. If you went out into the Amazon and gave IQ tests to random villagers they wouldn't get why you were asking them ridiculous questions. The field of Psychology is only recently taking cultural considerations seriously, and unfortunately the answer is that people from different cultures perform very differently on a wide variety of tests (sometimes they have biases Westerners don't, sometimes that lack biases Westerners have), and IQ tests are the worst offenders.

@asdf I have a high IQ but I cannot kill dangerous critters at will from orbit. It is Western culture that provides us with the benefits you listed.

An astounding ignorance of IQ on display here. The research on the subject is very rigorous and thorough and I encourage you to read it. IQ has nothing to do with Western culture and correlates strongly not just with "life" success, but with success in a whole host of areas like learning various skills. It is very closely linked with g, the measure of cognitive intelligence. Simply put, IQ does have meaning because, stripping out other factors, it is highly predictive of your ability to be productive and enjoy a high standard of living. There is no serious question about that.

Not_scottbot, again your ignorance of genetics it astounding. Please do not pollute the comments with your uninformed nonsense. There is only one human SPECIES (to which neanderthals also belonged) and therefore all humans can breed with one another of course. But there are many well defined genetic populations that differ significantly in phenotype.

It is the purest ignorance to believe otherwise, this is very well established in the scientific literature. A person of West African descent will have, on average, very different characteristics from a person of East Asian descent. You can tell by looking at them! It is unbelievably foolish to believe that the genetic differences would be only skin deep. That is a willful ignorance of reality.

It seems to me, the reigning hypothesis until shown otherwise, should include that IQ tests simply don't test an intrinsic genetic human trait, meaning the explanation is due to one of the many environmental differences between growing up in a developed country or an undeveloped one.

I am under the impression there is ample evidence for this, but I'll name just one: even in developed countries IQ scores have been rising with time.

Well I guess the progression of comments was pretty unsurprising. The left-wing IQ-deniers rush in and instantly jump straight to "BLACK PEOPLE!" as if every IQ debate revolves around those of African descent. Looking at lefty writings on the subject you'd swear that the only two continents in the world were Europe and Africa. Won't be long before someone comes in with the traditional "race is a social construct!" argument as if that matters.

Anyway, in the "environment vs genetics" debate I lean very heavily towards "environment", but it seems incredibly silly to deny ANY genetic involvement. And why does it matter, ultimately? Knowledge of averages for people who share a particular trait doesn't mean you're going to run out and apply those averages to everyone with that trait. There are very few situations where knowledge of those averages is useful.

@Ken how is it a problem with IQ?

Indeed, humans are not as good pigs as pigs, and not as good at smelling and unearthing roots. That does not invalidate the fact that humans are cognitively superior to pigs due to their genetic differences, and that this superiority founds their dominion over pigs as well as the rest of nature.

Curt Doolittle thinks diet doesn’t affect IQ. I hope he’s ok with his kids eating lead paint.

But on to the larger issue, obviously some individuals are smarter than other individuals. But, what there isn’t any good evidence for is that black people are on average dumber than other people because of their genetic makeup.

It’s patently obvious that there’s a large ideological component to the "social sciences," that’s why we see Noble prize winning economists coming up with opposite policy recommendations. Psychology has the same problems as economics.

The much more interesting question is, why do so many right wingers want so badly to believe that black people are genetically dumber?

IQ is the phrenology of the current age.

From Discover mag blog:

“Indeed, as I alluded to earlier, this new paper is the latest in a long line of hypothesis-generating publications from Fincher and Thornhill linking parasites and infections to pretty much any sweeping aspect of human life you can think of. Through similar studies based on correlations at the national level, Thornhill and Fincher have suggested that infections are linked to individualism and collectivism, religious diversity, linguistic diversity, armed conflicts and civil war, and democracy and liberal values.†


Though I attempted to stay in order, this needs to be emphasized -
'The word "race" still encapsulates a valid concept, but at this point, has too much connotational baggage for the emotional neutrality appropriate to good science.' The valid concept rests on the idea that classification by various criteria can yield scientifically meaningful perspectives - the emotional baggage is more like the historical reality of what happens when classification becomes justification. Along with the fact that those wedded to the idea that there must be more than one human race are promiscuous in using any source to justify their conclusion.

'but if you're saying individuals don't have genetic ancestries that can be classified objectively'
Of course they can - all the way back to the population bottleneck which seems to have created the human race.

'You can tell by looking at them!'
Actually, at least in the state I was born, you didn't even have to look - one drop of blood defined as black meant you were black. Which is strange, really, since we all have African ancestors (I trust that isn't too controversial to state as fact for some of the people commenting here) - no one was half white, or any other mixture (other cultures have much more, precise?, terms in how to detail degrees of mixing among people), they were all black as long as any black ancestor could be identified (the Jefferson family remains a fascinating reminder of how this works in practice, by the way). And the existence of such children needed to be prevented, but in those days, it was the marriage that was illegal (as was unmarried sex in the Commonwealth, of course), and not the resulting child - but hey, why get derailed in marriage/miscegenation technicalities, back when racism wasn't just politically correct, it was the law in many states.

'a population is a race when its members share more common ancestors together than they share with a random member of the larger reference population.'
Well, nice to see how tautology remains the cornerstone of a certain worldview. Though how this statement prevents my family from being a race in comparison to your family isn't quite clear.

For anyone interested in a fairly decent overview of how humans (that's right, all of us - sorry to have the restate the obvious) evolved, at least in the eyes of the authors of the paper, this is a nice link - http://mbe.oxfordjournals.org/cgi/content/full/17/1/2 One of the more interesting points is how Europe was most likely depopulated, possibly several times, in the Late Pleistocene (that's right, homo sapiens took a while to actually expand into Europe, and it looks like southern Africa didn't work out the first time either). Which makes one ask the question - how many races are there in Europe? Or doesn't, since the answer is simple - just one. However, I must also point out that this is also the perspective shared by the authors, so for some of you, reading both the main article and its copious links would likely be a waste of time, as facts aren't really the point of this discussion, are they?

'that there are differences in intelligence between groups, that natural selection brought about.'
Because literacy is a matter of natural selection? Because access to schools as a child is a matter of natural selection? Because IQ tests, as compared to survival (which, come to mind, seems to be the only criteria to such uninformed individuals as Darwin), are part of natural selection? These aren't the sort of objections that are easily dismissed as being from the 1970s, though of course, you are welcome to keep your cherished beliefs that some groups have to be clearly different if it comforts you.

'...the Economist recently reported that China has no such qualms and proceeding full bore ahead.'
I do wonder if they will be able to build on the extensive work done in the early 20th century in the Commonwealth of Virginia, much of which was translated into German, and then used by a society with even less qualms than today's China in terms of human improvement - well, those that were considered human. Sadly, I doubt that even 1 out of 10 posters here could pass that society's strict measures of racial purity, much less belonging to the proper race. Sorry, any Irish, Italian, or French ancestry means you simply aren't a member of the correct race, though as a courtesy, you won't get insulted - unlike the mongrels they thought inhabited the U.S.

Welcome to the social construction of race in modern history - which so many people here seem thoroughly attached to.

It takes an IQ of 122 to invent a machine, at least, that's what it appears to take. It takes 110 IQ to get a liberal education (the classics). It takes 105 to repair a machine. Everyone else uses machines. From this perspective, iq distribution matters desperately for any civilization. The more people you have above 100 as a percentage of your population the better off you will be in an industrialized society.

This is the funny thing about the IQ debate. The belief in specific cut off points. So a person with a 121 IQ could not invent a machine. A person with a 123 could. Seriously?

i've got the ouija board. let's get stephen jay gould on the horn.

Race, race, race...ad nauseam. Not one word about culture - not one word about which attitudes and behaviors are encouraged and which are discouraged in various cultures. Culture (or ethos) cannot be excluded as a major influence upon, if not a determinant of, the IQ of various populations.

all those jumping on not_scottbot need to go back and actually read the post he put up. he's attempting to explain the racist way of looking at those they think themselves superior to. he is NOT attempting to put forward a racist rant. sheesh. i think the IQ of many posters here should be double checked if they cannot even comprehend such a posting.

There is always much confusion about what the definition of racial group is. The simplest, most useful definition is that a racial group is an extended family that is partly inbred.

Juan Eschar: Species is somewhat discretely defined, in so far as you can give it a cut and dry definition with interbreedibility. But even then, yes species is ultimately kind of arbitrary. The discreteness of species is only the case because the intermediate ancestors have died. And this is not always the case: there exist ring species, where A can interbreed with B and B can interbreed with C but A cannot interbreed with C, where figuring out where to draw the species line is quite arbitrary. (And of course, you also have things like mules, where different species can breed but not very effectively.) Species is an extremely useful classification system, but there's plenty of arbitrariness to it.

But race is, of course, even more arbitrary, because all races interbreed. There are certain points where you can say that interbreeding has historically been far less common (native Americans prior to Columbus were rather separate from the rest of the world, for instance) but generally speaking it's much more arbitrary deciding which branches of the tree of life are sufficiently distinct to be called races.

"But race is, of course, even more arbitrary"

And extended family is, of course, even more arbitrary than race, yet we don't deny the existence of extended families nor their importance.

All the conceptual objections to the existence of racial groups are even more telling against the existence of extended families. Yet, nobody doubts that extended families exist.


maybe a purple red snake? :) [see Terry Pratchet's quote above]

Look, testing is an enormous business these days. Every single test designer in America knows that he would get rich if he could be the one who finally comes up with a test that retains predictive validity at forecasting achievement yet simultaneously gets rid of disparate impact on blacks and Latinos.

The Supreme Court's Griggs decision inventing disparate impact law was almost four decades ago, so eliminating disparate impact (without ruining predictive validity) has been the Holy Grail of test designers for a generation and a half.

For example, ETS hasn't asked that legendary SAT vocabulary question about "regatta" since the early 1970s.

Yet, nobody has succeeded in much reducing disparate impact.

Why not?

The answer is straightforward but unpopular: because, on average, blacks and Latinos continue to achieve less in the real world, so tests with high predictive validity at forecasting achievement have high disparate impact.

Re: What is race? Please see the following post: http://www.gnxp.com/blog/2007/01/race-current-consensus.php.

Please spend some time at that site if you want to know what SCIENTISTS think and know. If you care about reality or truth- look at the science please.

Meanwhile, Cowen can enjoy how the iq racism spreads to Germany in general and Berlin in particular from his homecountry. See Sarazin etc....

The funniest part is when Jews think they get the better end of iq racism and become zealous advocates when they get asigned the higher ones, oh fools they are.

'And extended family is, of course, even more arbitrary than race'
It most certainly is not - we are all members of the same extended family, even if some people seem to have an extremely hard time understanding this reality. But this is true in another sense, to the extent that when 'extended family' relies on something other than direct DNA evidence, it can be very inaccurate - as a certain somewhat hushed up British study of true maternity in a village setting demonstrated, or to remain on point with an earlier example, Thomas Jefferson's extended family.

'improving the IQ of poor people, such as, in the Third World, fighting hookworm and fortifying staple foods with iodine and iron.'
And this is where Sailer is at least someone to engage - regardless of the slippery slopes he goes up and down, it does not appear as if he is actually a mean spirited social darwinist in the very familiar 20th century model. And breast feeding should be encouraged for all mothers, so this too is a reasonable contribution.

But then, Sailer writes this -
'because, on average, blacks and Latinos continue to achieve less in the real world, so tests with high predictive validity at forecasting achievement have high disparate impact.'
I guess our president has a half full glass, because let's be honest, when Obama was born, there would have been no need to test any African-American for their suitability to hold any elected position, much less the office of the presidency of the United States of America, particularly in those fine states of the Confederacy. The very idea of a black man being elected to such a position, regardless of any testing with 'high predictive validity at forecasting achievement' would have been considered prima facie inconceivable. Even developing such a test would have been thought a clear waste of money and effort. Yes, Sailer has given himself an out with 'average,' but the reality described of America in the early 1960s remains - there was no need to develop tests which would rest on such an absurd basis as a black man (and remember, in those fine states of the Confederacy, Obama, Obama's children, Obama's grandchildren, and on and on, are nothing but black, regardless of who they marry and have children with - meaning that maybe the idea of both extended family and race are actually more entwined than some wish to acknowledge) having the talent and skill to be elected to the Senate, much less the Presidency. After all, there were laws in place throughout those fine secessionist states to prevent just such an inconceivable situation before it could arise, and some of the supporters of such laws undoubtedly felt themselves to be merely following the clear dictates of scientific thought as expressed by scientists proud, at the beginning of the 20th century, to proclaim themselves racists guarding a self-evident purity of essence. (Like keeping all those East Europeans out, as clearly, Poles and Czechs and Hungarians were inferior when measured against the standards of those white scientists.)

Then this - 'The simplest, most useful definition is that a racial group is an extended family that is partly inbred.' Notice the 'racial group' - not group, mind you, but racial group. And partly inbred - which could also be expressed a bit differently to mean a lack of external mixing, a mixing which is happening much more concretely on some continents (both Americas, particularly) than others. Which leads one to wonder - how many 'racial groupings' live in Indian? 50? 1000? Anyone ever bother to check? Or would it be enough to just count the various castes to determine the 'racial grouping,' as caste represents an extended family which is intentionally inbred. But such a clearly social construction of 'racial grouping,' including how it originates and perpetuates, doesn't fit well into the worldview of those who refuse to believe that there is only one human race.

not_scottbot, You didn't read my links, did you? You are not responding to what I and others are saying, but just going off on your own tangent. I was not alive in the '60s and I am not a racist, but I am not willfully blind and ignorant either.

not_scottbot: "Well, this is already the first mistake - neither Czechs, nor Kenyans nor Italians not Finns are a race, though they are nationalities, and very often, the nation state has attempted to justify nationhood in the spurious notion of race."

I would just like to point out that the Finno-Ugric cultural/linguistic/genetic group is reportedly distinguishable from Indo-Europeans. I'm half German and a quarter Finnish, and I'd like to learn both languages. However, I have lower expectations for my ability to learn Finnish, since it apparently doesn't have a common base with English like German does.

At GNXP it was argued that one can't plausible explain both the gap between whites & african-americans as well as with africans in a 100% hereditarian manner. But I think that was using old african scores which Steve is saying are inaccurate:

Sailer discussed differential item score here:

M Schwartz:

I thought I'd reply to some of the nuggets of wisdom most recently.

First, I'd like to say this research is absolutely nothing special, because the link between IQ and disease has been known for.... ages. If you ever get sick, your mental functioning will probably be impaired. The high prevalence of hookworms in the south was known to lower IQ, for example.

"Maybe an implication of evolution in different cultures and environments for the last 50,000 years or so?"

Of course it is, but not the way you allude to. You act like differential evolution leading to IQ differences is going to lead to mean they're immutable. I'm surprised you actually mentioned cultural evolution, though- up until recently, many people of your stripe have often been obsessed with the ice ages creating every IQ difference imaginable. Except the really blatant ones that can't be explained by it, like jews.

"The Chinese will likely be the first to answer this question:"

Which is nothing special. Look, you people act like finding out the underlying genes for IQ is going to be some out and out telling point when there's plenty of evidence for such things already- heritability studies. Now, I'm not one to make major pronouncements, but I can't help but doubt the idea of the idea of IQ being largely fixed being the dominant consensus among behavior geneticists and the like, and if you were to go to any university department relating to that, it'd be a bastion of hereditarianism full of jensen fans.

The average heritability of IQ in the modern first world is .7-.9, meaning about 8 to 5 points are due to environment. That's quite abit due to alot of variable environmental influences spread over the lifespan, but once again, I'm not one to make pronouncements.

Though, there goes that fetishization of china's disregard of "western PC"- what could china do wrong?


I find the controversy over SS african IQ scores to be a funny one. People like Lynn think the IQ of around 70 is due to disease and poor malnutrition and the like, thus strongly phenotypic, while people like Jensen and Rushton think it's genotypic. Basically, the proponents of that score can't seem to make up their minds as to what it remotely means.

Regardless, Lynn seems to seldom implicate the "around 70" figure into his evolutionary theories of IQ, and likewise seldom extends these strongly phenotypic variables to other populations. Nor does he even do a detailed analysis of how the various diseases, forms of malnutrition etc. affect IQ in SS africans. He acts like it's so linear and widespread.

And Jensen and Rushton emphasize it being genotypic by their examination of SA university students- of course, it begs asking how they were able to generalize the selectivity of "african universities" as being so high to so much of the continent, or considered that the ANC might have heavily lowered standards. And what's the deal with them mentioning greater instructions for all groups greatly raised IQ? Is that just teaching to the test? If so, why mention it? If not, why constantly talk about the much lower earlier scores?

Regardless, Wicherts seems to have done some interesting analysis' on these studies.

I could write more and more about the african IQ scores, but these are some general points. I also think SS african IQ scores would probably be ALOT lower if their genotypic IQ's were around 70. Why? Because the disease and malnutrition is lowering an already very low IQ.

I also think the point people like Sailer make about arguing for a higher score for SS africans working in favor hereditarianism to be ridiculous. The conditions in SS africa are undoubtedly known to lower IQ, albeit in a largely phenotypic and extreme fashion, (poor education also plays a role) and thus, most of those factors aren't applicable to the modern first world. This also acts like IQ differences just have to be so heavily explained by cartoonishly traditional explanations- "SES", "schooling" etc. and have to be washed away, overnight, somehow, because even the slightest admission to them being slightly genetic, and not disappearing overnight, is some astounding validation for your beliefs.

Regardless, Wichert as well believes the score of around 80 is probably strongly phenotypic in origin as well.

And when I say phenotypic, I mean IQ differences that are due mainly to extreme environmental influences- genotypic being the kind of differences you see in the modern first world, where those conditions apply less. Undoubtedly, IQ has a significant genetic component, albeit it can be relatively variable even within the modern first world. The same obviously holds true for race differences in the modern first world. To spout the old cliche, a high heritability doesn't imply immutability, but I'm not one to exploit the vague data on between race heritability to use as an ace in the hole. The high heritability is simply the average difference found in the modern first world and doesn't say much regarding more differentiated and narrow focused environmental influences.

M Schwartz again:

"Curiously, the parasite>IQ link is found in 5 out of 6 regions. The exception was South America. The correlation collapsed completely there. Why? Because the South American region included several Caribbean nations almost wholly inhabited by Africans. So why were the results there different from the rest of South America?"

Well, this is from John Jay Ray, not Schwartz. But anyway...

The study is strongly based on L&V's data, and to a lesser extent, Wicherts data. Since L&V think afro-carribeans also have IQ's of around 70, well, therefore parasites don't lower IQ! Nevermind how much of the carribean data is even vaguer than the data in mainland SS africa, (there's alot of evidence suggesting the B-W gap is alot smaller in the UK, yet L&V think it's virtually identica: http://racialreality.blogspot.com/2010/06/united-states-north-south-achievement.html) the conditions of many countries, states and territories with significant or majority black populations aren't anywhere what would supposedly be expected of that score.

A favorite of racialists is Haiti, yet they never seem to tell us how no other significant or majority black state in the carribean even approaches it. The closest is Jamaica, yet that's still worlds above- something like a general second world country. Many are quite developed, like Barbados, St. Lucia and Bermuda.

"John Ray also notes:"

The kids in the dutch famine study were probably hospitalized for malnutrition. The effects of malnutrition can be remediated if given treatment soon enough. Guess what malnutrition also leads to? Terrible immune system function and all sorts of physical ailments. People who suffer with those life long are those who have gone without treatment for ages.

Look, it's beyond dispute that malnutrition lowers IQ. Google it. Ask any doctor or anybody even remotely versed in health and nutrition if it does, or if it impairs any form of mental functioning. Better yet, go without eating for awhile and tell us if you can think that clearly.

It's truly amazing the lengths some will go to prove the "IQ of around 70" figure or so many national outcomes as being due to IQ and little else.

I also like how Ray basically says "well maybe it's because dumb people can't manage themselves???" There is indeed a link between IQ, health, and longevity, but it's quite weak overall. I mean, isn't the life expectancy for african-americans only several years below that of whites?

You also can't extrapolate the correlations between longevity and IQ to such different situations. The correlation between IQ and longevity has only really risen in recent decades due to substantially greater equalization of health care and overall environmental improvement. IQ meant astoundingly little for longevity in a pre-modern urban society, even 1800's england, which is what many parts of SS africa resemble. (but it's because they have IQ's of around 70 and not much else, right???)

Of course being ill doesn't give you the energy to concentrate. Diet may also be a factor if nutrients are lacking. www.chronicacne.net

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