Racial differences in intelligence from the author of The Bell Curve

[The_Flying_Dutchman]

See http://www.bsd.uchicago.edu/newsarchive.html#lahn2

[John_Mace]

@The Flying Dutchman

That would be logical if we assume our genome is fixed.

The last time I looked into this topic about a year ago, the breaking news was the discovery of a brain gene variant of microcephalin that appeared in the human population 37,000 ago outside of Africa. Googling now, there appears to be a lot of scientific speculation that 70% of us inherited this variant from neanderthals who did not inhabit Africa.

Nor did they inhabit most of Asia or any of Australia, and yet Asians typically score higher on IQ tests than Europeans. Although this stuff is always interesting, it’s important not to read too much into it. From your cite:

“By no means do these findings constitute definitive proof that a Neanderthal was the source of the original copy of the D allele. However, our evidence shows that it is one of the best candidates,” Lahn said.

Not “the best candidate”, but " on of the best candidates".

[tomndebb]

On the other hand, last spring one study group indicated that Normal variants of Microcephalin and ASPM do not account for brain size variability, (even noting in the article that brain size began to shrink in about the same time frame as the apparent introduction/mutation of MCPH1 and ASPM).

They were also a bit vague on distribution. The European/Neandertal meeting occurred after the primary human migration toward Asia was well under way, (although migration and return across similar latitudes might allow for more inter-group dispersion), so the smaller frequency among Africans is simply noted when excluding them from the analysis with no actual explanation provided.

[Steve_MB]

@Charles Murray

When a statistical procedure, blind to physical characteristics and working exclusively with genetic information, classifies 99.9 percent of the individuals in a large sample in the same way they classify themselves, it is hard to argue that race is imaginary.

They found people who had never heard of the traditional concepts of “race”, gave them no information other than the genomes, and they came up with a genome-based division that corresponds closely to the traditional concept?

If so, Murray is correct.

If not, Murray is being intellectually dishonest.

[John_Mace]

@Steve MB

They found people who had never heard of the traditional concepts of “race”, gave them no information other than the genomes, and they came up with a genome-based division that corresponds closely to the traditional concept?

If so, Murray is correct.

If not, Murray is being intellectually dishonest.

Except “social construct” ≠ “imaginary”. The reason we say that race is a social construct is not because we don’t think there is any genetic basis, but that there are other overriding factors that are not genetic. We call Halle Berry “Black”, but she almost certainly derives more from European than from African ancestry. We call Europeans “White” and Indians (from India) “Asian” even though Indians are closer genetically to Europeans than they are to Chinese. Some Indians are darker skinned than most American Blacks, but we don’t call them “Black” and, if anything, we’d have to call them White.

In speaking of race in the US, we usually mean Blacks and Whites, and we act as if there is a strict dichotomy-- you’re either White or Black. But that is far from what the genetic data would tell us. The main problem with “race” is that for it to have any real meaning, genetically, we’d have to define dozens of races that correspond to genetically similar ethnic groups around the globe, and even then there would be dozens of ways of slicing and dicing that data resulting in mnay different racial schemes. There isn’t any place where you can draw a line and say people on that side of the line are of race A and those on the other are race B, except in a completely arbitrary manner.

[Shalmanese]

@eponymous

Which is bullshit - Lewontin and others ARE NOT saying that race is imaginary - what they have said repeatledly is that race is a social construct, that THERE IS NOTHING COHERENT about the concept of race (as it is commonly understood in layman’s terms) from a biological/genetic perspective. Which leaves the question of whether race is coherent or useful from the cultural/sociological perspective unaddressed. I don’t think Lewontin and others are arguing that one CAN’T examine race from this (cultural/sociological) perspective, just that it doesn’t make much sense in examining the concept of race from a genetic/biological perspective.

Except that there now is something coherent about the concept of race because it can be used as an accurate predictor of drug interactions and it’s becoming possible to make drugs “tailored” to different races. This is all relatively recent research so it’s understandable that Lewontin didn’t know about this but now that this research is out there, what Murray is trying to say is that the continual claim that “race is a social construct” is empirically false.

@Lissa

That wouuld be my first reaction-- to point to social causes: that black Americans tend to be poor and thus are affacted from childhood by poor nutrition, educational/socialization disadvantages and other environmental factors which would have an impact on adult intelligence.

What other causes could there really be? I’ve never heard any suggestion that the brains of African-Americans have less synapses or any other physical difference which would hinder intelligence.

Murray goes into this in his article and claims that if this were the case, then blacks would score low on the less g loaded parts of the test and higher on the highly g loaded parts as these are meant to be more of a measure of inherent intelligence. However, his claim is that the exact opposite is true:

When you compare black and white mean scores on a battery of subtests, you do not find a uniform set of differences; nor do you find a random assortment. The size of the difference varies systematically by type of subtest. Asked to predict which subtests show the largest difference, most people will think first of ones that have the most cultural content and are the most sensitive to good schooling. But this natural expectation is wrong. Some of the largest differences are found on subtests that have little or no cultural content, such as ones based on abstract designs.

As long ago as 1927, Charles Spearman, the pioneer psychometrician who discovered g, proposed a hypothesis to explain the pattern: the size of the black-white difference would be “most marked in just those [subtests] which are known to be saturated with g.”[58] In other words, Spearman conjectured that the black-white difference would be greatest on tests that were the purest measures of intelligence, as opposed to tests of knowledge or memory.

A concrete example illustrates how Spearman’s hypothesis works. Two items in the Wechsler and Stanford-Binet IQ tests are known as “forward digit span” and “backward digit span.” In the forward version, the subject repeats a random sequence of one-digit numbers given by the examiner, starting with two digits and adding another with each iteration. The subject’s score is the number of digits that he can repeat without error on two consecutive trials. Digits-backward works exactly the same way except that the digits must be repeated in the opposite order.

Digits-backward is much more g-loaded than digits-forward. Try it yourself and you will see why. Digits-forward is a straightforward matter of short-term memory. Digits-backward makes your brain work much harder.[59]

The black-white difference in digits-backward is about twice as large as the difference in digits-forward.[60] It is a clean example of an effect that resists cultural explanation. It cannot be explained by differential educational attainment, income, or any other socioeconomic factor. Parenting style is irrelevant. Reluctance to “act white” is irrelevant. Motivation is irrelevant. There is no way that any of these variables could systematically encourage black performance in digits-forward while depressing it in digits-backward in the same test at the same time with the same examiner in the same setting.[61]

Murray also claims that brain size adjusted for body size is positively correlated with IQ (r = 0.4) and that blacks do have measurable smaller brains. This is a much weaker line of argument as it doesn’t follow that these two are cross correlated but the possibility exists no matter how much like bad phrenology it sounds.

@BrainGlutton

I recall reading in The Bell Curve Wars – or perhaps it was another book called The Bell Curve Controversy, which I got from the library a few years ago but now can’t find on Amazon – that many Third-World countries have shown a one standard-deviation increase in measured average IQ since WWII, and without any significant change in their gene pools; the improvement can only be attributed to improved nutrition, education, sanitation and health care. Furthermore, a study of children fathered during WWII by black American soldiers on German women, and raised in Germany as Germans, shows no significant difference between their IQs and the general population’s.

So if black Americans have a measured IQ bell curve significantly to the left of white Americans’ bell curve – and they do, that part is not even controversial – I think the likeliest explanation for that is not that they are mentally inferior by heredity, but that growing up black in America is like growing up an average citizen in an underdeveloped country – you just don’t get the opportunity to fully develop your mind’s potential.

Murray claims that cohort studies (ie: those studying blacks and whites in similar Socioeconomic Status) in America still reveal a systematic black/white difference.

@Valteron

I am sometimes called upon to recommend people for hiring or to hire people for specific contracts. Now as a rule, I hire one or two persons at a time, so I judge them on their interview performance, their skills, or certain tests I administer.

Now as I understand, none of these scientific examinations of race and IQ have ever infered that any given member of one race is necessarily smarter than any given member of another race. So the average IQs of one race compared to another would not be of much use to me in identifying good potential employees.

But if ever the day comes that I am called upon to fill a couple of billion jobs and that I decide to fill them with every member of the white race or the black race or the yellow race, or what have you, I would find these scientific studies of enormous value in making my decision. :rolleyes: :rolleyes: :rolleyes:

Murray specifically addresses this:

I will focus on two sorts of differences: between men and women and between blacks and whites. Here are three crucial points to keep in mind as we go along:

1. The differences I discuss involve means and distributions. In all cases, the variation within groups is greater than the variation between groups. On psychological and cognitive dimensions, some members of both sexes and all races fall everywhere along the range. One implication of this is that genius does not come in one color or sex, and neither does any other human ability. Another is that a few minutes of conversation with individuals you meet will tell you much more about them than their group membership does.

2. The concepts of “inferiority” and “superiority” are inappropriate to group comparisons. On most specific human attributes, it is possible to specify a continuum running from “low” to “high,” but the results cannot be combined into a score running from “bad” to “good.” What is the best score on a continuum measuring aggressiveness? What is the relative importance of verbal skills versus, say, compassion? Of spatial skills versus industriousness? The aggregate excellences and shortcomings of human groups do not lend themselves to simple comparisons. That is why the members of just about every group can so easily conclude that they are God’s chosen people. All of us use the weighting system that favors our group’s strengths.[1]

You are attacking a straw man and one he specifically refutes at the very beginning of the article.

@pantom

Perhaps the strongest evidence against a genetic basis for intergroup differences in IQ is that the average level of mental test performance has changed very significantly for whole populations over time and, moreover, particular ethnic groups within the population have changed their relative positions during a period when there was very little intermarriage to change the genetic makeup of these groups.
While The Bell Curve cites the work of James R. Flynn, who found substantial increases in mental test performances from one generation to the next in a number of countries around the world, the authors seem not to acknowledge the devastating implications of that finding for the genetic theory of intergroup differences. . . .
The national averages have in fact changed by amounts that are comparable to the fifteen or so IQ points separating blacks and whites in America. To put it another way, on the average, whites today differ from whites, say, two generations ago as much as whites today differ from blacks today. Given their size and speed, the shifts in time necessarily have been due more to changes in the environment than to changes in the genes.
. . . When any factor differs as much from Al to A2 as it does from A2 to B2, why should one conclude that this factor is due to the difference between A in general and B in general? That possibility is not precluded by the evidence, but neither does the evidence point in that direction.(2.)

Murray specifically addresses the Flynn effect argument:

The third implication is that the “Flynn effect” will not close the black-white difference. I am referring here to the secular increase in IQ scores over time, brought to public attention by James Flynn.[72] The Flynn effect has been taken as a reason for thinking that the black-white difference is temporary: if IQ scores are so malleable that they can rise steadily for several decades, why should not the black-white difference be malleable as well?[73]

But as the Flynn effect has been studied over the last decade, the evidence has grown, and now seems persuasive, that the increases in IQ scores do not represent significant increases in g.[74] What the increases do represent–whether increases in specific mental skills or merely increased test sophistication–is still being debated. But if the black-white difference is concentrated in g and if the Flynn effect does not consist of increases in g, the Flynn effect will not do much to close the gap. A 2004 study by Dutch scholars tested this question directly. Examining five large databases, the authors concluded that “the nature of the Flynn effect is qualitatively different from the nature of black-white differences in the United States,” and that “the implications of the Flynn effect for black-white differences appear small.”[75]

These observations represent my reading of a body of evidence that is incomplete, and they will surely have to be modified as we learn more. But taking the story of the black-white IQ difference as a whole, I submit that we know two facts beyond much doubt. First, the conventional environmental explanation of the black-white difference is inadequate. Poverty, bad schools, and racism, which seem such obvious culprits, do not explain it. Insofar as the environment is the cause, it is not the sort of environment we know how to change, and we have tried every practical remedy that anyone has been able to think of. Second, regardless of one’s reading of the competing arguments, we are left with an IQ difference that has, at best, narrowed by only a few points over the last century. I can find nothing in the history of this difference, or in what we have learned about its causes over the last ten years, to suggest that any faster change is in our future.

@Steve MB

They found people who had never heard of the traditional concepts of “race”, gave them no information other than the genomes, and they came up with a genome-based division that corresponds closely to the traditional concept?

If so, Murray is correct.

If not, Murray is being intellectually dishonest.

My understanding is yes, they gave this data to a computer with no concept of race and asked it to find clusters in the data. The clusters found corresponded well to self-reported race.

[eponymous]

@John Mace

That is a common misconception. What they were able to do was to trace the maternal and paternal lines of various people back to their likely geographic region of origin. But those would only be 2 ancestors (one famale, one male) out of the many ancestors that person would have had from 200 -300 years ago.

You are correct - I was going mostly from memory. If I recall correctly, Chris Tucker had the strongest case (compared to the others from the program) of his ancestors likely coming from a population originating somewhere in Angola.

The host of that show, Louis Gates Jr., was found to have had paternal and maternal lines that originated in Europe, but he was still determined to have had about 50% of his ancestory from Africa. It was just really hard to pinpoint where in Africa that genetic component came from. It would be no different than telling a White person with the last name of O’Neill that he was Irish, even if his family had been in the US since long before the Civil War and he had no idea whether he has that last name because of one Irish ancestor from 150 years ago, or whether all of his ancestors hailed from Ireland. Assuming 25 years per generation, that person could be as little as 1/64 Irish.

You are right - I think for Gates there were several geographical regions within Africa that were likely candidates. I believe the one that had the strongest link (although not conclusive) was in Northern Africa near the Mediterranean. Again, going from memory, so I could be wrong…

[tomndebb]

@Shalmanese

Except that there now is something coherent about the concept of race because it can be used as an accurate predictor of drug interactions and it’s becoming possible to make drugs “tailored” to different races.

Really? I have seen no evidence of that.

There was the recent (couple years back) approval by the CDC to conduct medicine trials on a particular medicine (BiDil) for black men in the U.S. based on one interpretation of the results of an earlier trial that showed more improvement among black males than white males. That sounds pretty impressive. Of course, when the test populations were re-evaluated for separate conditions that ignored race, they actually found a better corerelation for improvements when it was based on prior medical history, age, current levels of wealth/poverty, and general health. Apparently, it is simply true that in the U.S., aging black males with heart problems have a lifestyle (diet and exercise) and access to medical care that is generally closer to the conditions that are helped by that medicine.
Politics has driven subsequent tests to be targeted to aging black males, but there has been no evidence to establish that “race” has been the primary factor in the medicine’s effectiveness.

Is there some other “race-based” drug that has gotten into the news?

(It is also possible that BiDil will, indeed, eventually prove to be more efficacious, in general among blacks in the U.S. However, before we jump to a claim of “race,” we need to demonstrate that it also works better on blacks in Brazil (who were generally imported from different regions in Africa) as well as blacks in Senegal, Tanzania, Ethiopia, South Africa, Mozambique, Congo, etc. In other words, establishing that a drug works well on the particular population of people who were primarily taken from the West Coast of Africa, then mixed with large percentages of Europeans and indigenous Americans may mean that that new population has developed certain characteristics that respond to a particular drug without making any statement about some rather larger group of people whom we arbitrarily shoehorn into a category labeled “race.”)

[Shalmanese]

@tomndebb

Really? I have seen no evidence of that.

There was the recent (couple years back) approval by the CDC to conduct medicine trials on a particular medicine (BiDil) for black men in the U.S. based on one interpretation of the results of an earlier trial that showed more improvement among black males than white males. That sounds pretty impressive. Of course, when the test populations were re-evaluated for separate conditions that ignored race, they actually found a better corerelation for improvements when it was based on prior medical history, age, current levels of wealth/poverty, and general health. Apparently, it is simply true that in the U.S., aging black males with heart problems have a lifestyle (diet and exercise) and access to medical care that is generally closer to the conditions that are helped by that medicine.
Politics has driven subsequent tests to be targeted to aging black males, but there has been no evidence to establish that “race” has been the primary factor in the medicine’s effectiveness.

Is there some other “race-based” drug that has gotten into the news?

From The NYT article

Race can also affect treatment. African-Americans respond poorly to some of the main drugs used to treat heart conditions—notably beta blockers and angiotensin-converting enzyme inhibitors. Pharmaceutical corporations are paying attention. Many new drugs now come labeled with warnings that they may not work in some ethnic or racial groups. Here, as so often, the mere prospect of litigation has concentrated minds.

[tomndebb]

Ahh! I confused two studies.

A 2001 study showed that enalapril was less beneficial to black patients than to white patients. It was that study that was re-evaluated without the race factor and demonstrated that a better correlation was found when checked by age, lifestyle, and availability to medical care than to race.

BiDil was never even tested on anyone but black heart patients. It is a combination of a pair of generic drugs that could not get FDA approval as a "new’ drug until the manufacturer pushed it as a drug for “black” patients and embarked on new trials to show that it would not harm blacks. When the trials came back showing that it had some efficacy (as it clearly would, it being already in use as separate drugs), the company was given the approval to market it as a “black” medicine.

So, do we have any actual “race specific” drugs of which I am not aware? Or do we simply have reporters printing hype from pharmaceutical companies looking for new markets?

[pantom]

First off, Shalmanese, putting forth a correlation of .4, in that brain size vs IQ sentence, as proving anything is, um, kind of weak. I do this stuff all the time as a kind of investment hobby, trying to find stuff that correlates and stuff that has a negative correlation, and if I don’t find an r-squared of about .6 or higher one way or the other, I just throw it out, since it probably won’t make me any money in a reliable way.
A few things that may be wrong, also, although it’s a bit unclear:

1 - R is not r-squared (unless by r you actually mean r-squared): that is, r is the correlation coefficient, r2 is the coefficient of determination: you can directly use r2 to say what percent of the dependent variable is predicted by the independent variable. Thus, in your example, .4 squared comes to .16, or 16% of the variation being explained, if what you cite is just r, in which case it’s not just weak phrenology, it’s weak statistics.
2 - If you have two independent variables, r2 will tend to be higher just by chance. You’d need to get adjusted r2 values, in that case. I’m assuming his sample size was large, in which case there really wouldn’t be much of a difference. Still, it’s suspicious that, if you’re interpreting correctly, he’s using r instead of r2 and - if he does have two independent variables in there - instead of adjusted r2. Sounds more like propaganda than it does any real attempt at gaining knowledge, if that’s the case.
3 - Finally, of course, there’s the old correlation not equal causation. I don’t know if nutrition bears on brain size, but if it does, that could explain that positive correlation, and it would be a far more logical explanation. And so on. Murray is making a claim that within a species with not a lot of genetic variation there is something going on genetically that determines that two subgroups of that species will have a genetically-determined variation that makes one less intelligent than the other. He needs to get some actual genetics to back him up. For such a strong claim, statistics, especially really weak correlations between different surface variations of different members of the species, is a sorry argument to make.

You only do statistics of this kind to establish that there’s an area that needs further investigation as to the cause of the correlation. I don’t know if scientists spend a lot of time looking for why two things have r2’s of .16, not being one, but I’d be surprised if they do. Admittedly, I use stats for entirely different pursuits, but it really doesn’t strike me as something worth tracking down, off the top of my head. I could be wrong.
(This of course also goes to Flying Dutchman’s thing about the allele affecting brain size. Even if everything he cites turns out to be true, we have a gene variation affecting a variation in brain size that has at best a weak correlation to IQ, and no one’s proved that that correlation means anything at all, yet, as far as I know.)

As for that quote you used against my Sowell quote, Sowell was directly addressing that quote from Murray you used. So, I guess we could go round and round that same quote, or just agree to disagree.

[The_Flying_Dutchman]

@pantom

(This of course also goes to Flying Dutchman’s thing about the allele affecting brain size. Even if everything he cites turns out to be true, we have a gene variation affecting a variation in brain size that has at best a weak correlation to IQ, and no one’s proved that that correlation means anything at all, yet, as far as I know.)

i never said anything about the allele affecting brain size. The gene does though, and we all have it.

I just wanted to point out to you that your reliance on African genetic diversity precluding a missing intelligence genetic variant is not well founded.

[pantom]

No, in fact it is well founded. At best your allele has a weak relationship to intelligence. The case that the Neandertals may have interbred with homo sapiens in the distant past is unproven so far, and the first analysis of nuclear DNA shows no apparent link, and that Neandertals may actually be more closely related to chimps than to human beings, which is as I expected, since my first thought was “if there was interbreeding, then Europeans would actually have comparable genetic diversity to Africans”.
But they don’t. Your exercise is best characterized as grasping at straws.

[David_Simmons]

@Gukumatz

All perfectly desirable blather, but, alas, this is currently about research. If there ever comes the time and place where someone tries to implement policy on this basis, I’ll be in lockstep with you, hippy flag a’waving. Until then . . .

Yes. A lot depends upon what you intend to do with sorting people into races. If it is to give extra effort to strengthening any weaknesses discovered by additional training in those areas, fine. If you intend to use the differences as a way of discrimination or channeling people into subsidiary roles then I have problems with the idea.

[Shalmanese]

@pantom

First off, Shalmanese, putting forth a correlation of .4, in that brain size vs IQ sentence, as proving anything is, um, kind of weak. I do this stuff all the time as a kind of investment hobby, trying to find stuff that correlates and stuff that has a negative correlation, and if I don’t find an r-squared of about .6 or higher one way or the other, I just throw it out, since it probably won’t make me any money in a reliable way.
A few things that may be wrong, also, although it’s a bit unclear:

1 - R is not r-squared (unless by r you actually mean r-squared): that is, r is the correlation coefficient, r2 is the coefficient of determination: you can directly use r2 to say what percent of the dependent variable is predicted by the independent variable. Thus, in your example, .4 squared comes to .16, or 16% of the variation being explained, if what you cite is just r, in which case it’s not just weak phrenology, it’s weak statistics.
2 - If you have two independent variables, r2 will tend to be higher just by chance. You’d need to get adjusted r2 values, in that case. I’m assuming his sample size was large, in which case there really wouldn’t be much of a difference. Still, it’s suspicious that, if you’re interpreting correctly, he’s using r instead of r2 and - if he does have two independent variables in there - instead of adjusted r2. Sounds more like propaganda than it does any real attempt at gaining knowledge, if that’s the case.
3 - Finally, of course, there’s the old correlation not equal causation. I don’t know if nutrition bears on brain size, but if it does, that could explain that positive correlation, and it would be a far more logical explanation. And so on. Murray is making a claim that within a species with not a lot of genetic variation there is something going on genetically that determines that two subgroups of that species will have a genetically-determined variation that makes one less intelligent than the other. He needs to get some actual genetics to back him up. For such a strong claim, statistics, especially really weak correlations between different surface variations of different members of the species, is a sorry argument to make.

You only do statistics of this kind to establish that there’s an area that needs further investigation as to the cause of the correlation. I don’t know if scientists spend a lot of time looking for why two things have r2’s of .16, not being one, but I’d be surprised if they do. Admittedly, I use stats for entirely different pursuits, but it really doesn’t strike me as something worth tracking down, off the top of my head. I could be wrong.
(This of course also goes to Flying Dutchman’s thing about the allele affecting brain size. Even if everything he cites turns out to be true, we have a gene variation affecting a variation in brain size that has at best a weak correlation to IQ, and no one’s proved that that correlation means anything at all, yet, as far as I know.)

Here is one of the meta-analyses cited which provides a correlation of 0.33. Another meta-analysis provides 0.40 but it’s hard to link to. A chi-squared test gives a p value of 0.003 that such a correlation could arise by chance. The general consensus, AFAIK, 0.3 - 0.5 counts as a “medium” strength relationship. Not exactly bulletproof evidence but not something you can just casually discard either.

The article goes into a whole lot more detail. That the correlation is greater for adults than children may suggest that upbringing could be a causative factor for both.

As for that quote you used against my Sowell quote, Sowell was directly addressing that quote from Murray you used. So, I guess we could go round and round that same quote, or just agree to disagree.

The Sowell quote was addressing the original Bell Curve arguments. The Muray quote seems to be directly addressing the Sowell quote and those like it.

[pantom]

If you’re right that .3 - .5 is considered medium (a 26% proportional rise/fall in the dependent is considered strong? Wow.), then their finding of .33 is on the very low end of that range. Their uncorrected number is .29, which falls below it.
From the text and the tables, it looks like they’re using r. The square of .33 is .1089, so they’re saying that 10.89% of intelligence can be “explained” by brain size. To me, that’s very low, but obviously I’m measuring on a different scale than these people.

[The_Flying_Dutchman]

@pantom

No, in fact it is well founded. At best your allele has a weak relationship to intelligence. The case that the Neandertals may have interbred with homo sapiens in the distant past is unproven so far, and the first analysis of nuclear DNA shows no apparent link, and that Neandertals may actually be more closely related to chimps than to human beings, which is as I expected, since my first thought was “if there was interbreeding, then Europeans would actually have comparable genetic diversity to Africans”.
But they don’t. Your exercise is best characterized as grasping at straws.

Pantom, you are absolutely missing my point. The only reason I mentioned the scientists speculating on the connection with neanderthals is because they are wondering how a genetic variant of a gene known to have an effect on brain size that is almost universal outside of Africa is somewhat rarer in Africa and arose after homo sapiens left Africa. The fact is there is a brain related genetic variant that arose outside the African genetic pool. ** Your claim that the greater African genetic diversity would make it not so has been proven absolutely untrue.** Whether or not microcephalin actually affects IQ or not is completely irrelevant to a rebuttal of your assertion.

[pantom]

I will concede your point, with a large stipulation:
I think, if I read you right, you’re saying that I said it would be impossible for some brain-related gene to arise outside of Africa, or some intelligence-related gene. If you go back and look at the final paragraph of my first post, it said the chances of Africans not having a gene that other homo sapiens elsewhere had were lower given their greater genetic diversity. Chances, not anything absolute. Or, to put it very simply, the higher the genetic diversity, the lower the likelihood some population is going to be missing some gene some other population has.
Combine that with the already low genetic diversity of the human race in general, and what you have is a situation where the claim that some yet-undiscovered gene that controls intelligence is present in the population outside Africa but absent in the population inside Africa becomes, if not extraordinary, certainly something that needs to be proven with a greater reliability than can be gotten with statistical studies.

[Shalmanese]

@pantom

Or, to put it very simply, the higher the genetic diversity, the lower the likelihood some population is going to be missing some gene some other population has.

On the face of it, this is absurd. The gene for blond hair is present in people outside of Africa yet not present for people in Africa.

[pantom]

Oh please. Yes, some things that are adaptive outside of Africa are going to be there, like blond hair, fat for Eskimo, and so on. This gene that Flying Dutchman is citing may be something like that, for all I know.
Intelligence, however, is a core human trait, like language or an opposable thumb.
Wait! Europeans have thumbs that are more opposable than Africans!
Sounds pretty absurd, doesn’t it?