Previously, I laid into James Watson for his comments on intelligence. But there is a greater spectre than Watson out there. Watson, for all his faults, at least can be said to have been bemoaning the state of affairs he was describing and argued against discrimination (although it’s hard to see how the world should change policies towards Africa based on that continent’s supposed lower intelligence and not call this discrimination). Most importantly, Watson paid for his comments (he was forced to resign the chancellorship of Cold Spring Harbor Laboratories) and later apologised publicly and, I believe, genuinely.

This is not, alas, true of most proponents of racial intelligence differences. To choose the most quoted recent example, William Saletan in Slate called the belief that intelligence is roughly equal across ethnic groups “Liberal creationism.” Here’s a taste of his writing:

…if you find the idea of genetic racial advantages outrageous, socially corrosive, and unthinkable—you’re not the first to feel that way. Many Christians are going through a similar struggle over evolution. Their faith in human dignity rests on a literal belief in Genesis. To them, evolution isn’t just another fact; it’s a threat to their whole value system…The same values—equality, hope, and brotherhood—are under scientific threat today. But this time, the threat is racial genetics, and the people struggling with it are liberals.

To Saletan, the evidence for different intelligence in different ethnic groups is as strong as the evidence for evolution.

Among white Americans, the average IQ, as of a decade or so ago, was 103. Among Asian-Americans, it was 106. Among Jewish Americans, it was 113. Among Latino Americans, it was 89. Among African-Americans, it was 85. Around the world, studies find the same general pattern: whites 100, East Asians 106, sub-Sarahan Africans 70. One IQ table shows 113 in Hong Kong, 110 in Japan, and 100 in Britain. White populations in Australia, Canada, Europe, New Zealand, South Africa, and the United States score closer to one another than to the worldwide black average. It’s been that way for at least a century.

Saletan has three other planks of evidence: (1) that IQ is partly inherited, (2) that people with bigger brains on MRI tend to score better on IQ tests, and (3) that some genes have been identified as affecting brain size and varying by continent. Now if the evidence for evolution was no better than this, creationism would still be the dominant scientific position and Charles Darwin would be known only to historians of science.

In a study released just this week, Robert Plomin announced that after an extensive scan of the human genome to find associations between intelligence and genes, he found only six genes that could be statistically linked, and the most powerful of these genes accounted for only 0.4% of variation in IQ. In other words, individual genes make very little difference to IQ; the genetic recipe for brains contains thousands of ingredients and complex, interlocking cooking instructions. Saletan could not have known about this particular paper when he wrote his article, but it doesn’t matter because this is only the latest in a long string of such evidence. Plomin was uncovering the same sort of evidence back in 1998.

Saletan argues that “If Africans, Asians, and Europeans evolved different genes, the reason is that their respective genes were suited to their respective environments.” Now we can see that Saletan isn’t just ignorant of the research base on intelligence and genetics, he knows virtually nothing about evolutionary theory. Groups don’t “evolve different genes”, they generate new genes by mutation. Genes change distribution in populations because of selection pressure, to be sure, but also because of neutral drift, and also, as I explained in the previous entry, founder effects. In the extreme case of the Ashkenazim, of whom you may recall half are descended from a total of four women, there are dozens of genetic diseases that came down that descent line not because they were beneficial for survival — how could they be? — but because those four women carried recessive genes that passed into their constrained lineage thus increasing the chances of their descendants getting two copies of the ill genetic variations. Had it been a different four women, Ashkenazim would have a different set of genetic illnesses associated with their bloodlines. This has nothing to do with natural selection and everything to do with historical contingency — what evolutionary scientists call “frozen accidents.”

And in what bizarre universe does being a hunter in Africa involve less advantage for intelligence than being a hunter in Europe or Asia? Here’s your answer:

If we lived in a savannah, kids programmed to mature slowly and grow big brains would be toast. Instead, we live in a world of zoos, supermarkets, pediatricians, pharmaceuticals, and information technology. Genetic advantages, in other words, are culturally created.

Over millions of years we became late maturers and big-brained. This happened while we were savannah dwellers. What happened 70-100,000 years ago that suddenly changed the selection pressures on the savannah? Saletan doesn’t say. Even more absurdly, Saletan seems to think that information technology went back in time and exerted evolutionary pressure on prehistoric humans. In Europe and Asia. Not in Africa. Not in the Americas. Not in Australia and the Pacific.

I’m not going to go point by point through Saletan’s many egregious errors. If you want that, you can check out this roundup of the many rebuttals of Saletan’s article at Noli Irritate Leones. I would prefer to do the flip side of last entry’s approach. Last time I Hammered the Worst Argument. This is a nice shortcut because it demonstrates that if, say, James Watson can believe such a stupid thing, then we can be duly skeptical about anything else he has to say on this particular subject. It does not replace a proper academic rebuttal but it’s a good shortcut.

This time I’m going to Hammer the Best Argument. That is, if I can blow Saletan’s best argument out of the water, then everything else he says can be safely tossed aside. Can I do it? You bet.

Saletan’s best argument is that there are large discrepancies in IQ scores between different ethnic groups. Of this, there is no doubt. The findings have been replicated many times over. There is broad consistency across many of the studies. So we can safely say that IQ scores do vary between different populations of humans. Now for the hammering.

The problem is that the IQ differences are simply too large to fit Saletan’s argument about intelligence and race. Let’s look at the difference between “whites” (by which Saletan means people descended from Western and Northern Europeans) and sub-Saharan Africans. This is the most important difference because (i) it is used to explain the terrible state of Africa today (remember Watson), and (ii) the vast majority of American blacks are descended from sub-Saharan Africans and therefore this finding applies to the major focus of racism in the US.

Let’s take Saletan’s figures at face value. The standard IQ score should average 100, for sub-Saharan Africans it’s 70. Let’s just graph that:

Now it should be immediately obvious from this graph that there is an enormous difference in those populations. In fact, what it means is that fully half the adult population of sub-Saharan Africa has an IQ that counts as a learning disability. In many states in the US, an IQ of 70 (sometimes 65 or 75, but mostly 70) is one of the criteria for establishing reduced moral culpability. That is, roughly half of sub-Saharan Africans would be considered to be born with mitigating circumstances should they ever face criminal trial in the US.

Let’s look at it another way: an IQ of 70 means concrete thinking and an inability to form abstract thoughts, it means poor appreciation of “wrongfulness”, it means limited independence, it means extremely limited ability to learn, and it means struggling to adapt to changes. It means half the population of sub-Saharan Africa has a “mental age” of twelve or lower. Does William Saletan really believe that if he walks down a street in Johannesburg, fully half of the adults he meets will be mild-to-moderately mentally retarded or worse?

It gets worse:

Half the sub-Saharan population scores lower than the bottom 2.2% of the standard population. Conversely, only 2.2% of sub-Saharan Africans reach the average American IQ. This is what Saletan would have you believe.

In Saletan’s world, high level IQ over 130 is uncommon at around 2.1% in the standard population, but exceedingly rare in sub-Saharan Africa (at six standard deviations, that’s around 1 person per billion). By his reckoning, the US currently hosts around 6.3 million people of high IQ. In comparison, sub-Saharan Africa with its population of 750 million people probably doesn’t have a single person with an IQ over 130. OK, maybe one. You don’t need to be a statistician to see how ridiculous this is.

It gets even worse. You see, Saletan based these figures on a 2005 summary of the evidence of IQ and race. That summary drew heavily on earlier summaries by Richard Lynn. That 2005 summary does not mention Lynn’s findings among racial groups that scored even lower than sub-Saharan Africans. The lowest scores were found among the Pygmies of the Congo, and their average IQ was reported to be 54. Now an IQ of 54 means severe intellectual disability. Most adults with an IQ of 50 not only cannot live independently, they cannot even live in the community. Most such adults require permanent institutionalisation. They cannot dress or prepare meals without help. Their communication skills are rudimentary. They can only be employed to perform simple repetitive tasks. And yet somehow, on the sort of evidence that Saletan uses, an entire ethnic group has survived for millennia in the wilds of the Congo despite the average adult not being able to learn how to tie shoelaces.

Remember, this is Saletan’s best argument. There is no reason to doubt that these IQ scores are genuine test results recorded by dedicated anthropologists and psychologists following good research techniques. What this tells us is not that Pygmies don’t average 54 or sub-Saharan Africans don’t average 70. What this tells us is that IQ scores do not measure what Saletan would like to believe.

Just to finish off, there is a nice bit of reverse racism in the new hereditarian movement. They gleefully quote the small increase that Asians get in IQ scores (average 105) and significant increase for Jews (average 113). You see how it works? “I’m white but I’m not claiming that my race is the best.” But you know, it doesn’t wash. If Africans are doomed to social catastrophe because of their low IQs, then it should equally follow that Asians and Jews should be lapping up the benefits of high IQ. So when can we expect the first Jewish US President? Jews only make up 2% of the American population — but if Saletan is correct and they get a free standard deviation then there should be around 8,300 Jews of “genius level” intelligence (IQ over 160) in the US compared to 9,500 whites. In other words, there should be nearly as many Jewish Presidents (and high achievers in any other field that benefits from high intelligence) as white Presidents.

Writers like Saletan point to the higher IQ scores of Jews and Asians only because they are of no practical significance except as a defence against charges of racism. It’s easy to concede that Jews and Asians are smarter when they don’t have practical access to the life success that their IQ scores are supposed to enable. This is, if I may remind you, the same life success that African-Americans are supposed to lack because of their low IQs. If there are extraneous factors such as racism or cultural differences that keep Jews and Asians out of positions of high success, it should be immediately obvious that there will be extraneous factors that complicate the position of blacks in the US and sub-Saharan Africa.

Either IQ is a major factor determining life (and national) success, in which case where are the Jewish Presidents and American-Asian CEOs (and why is China catching up on industrialisation six generations behind Scotland)? Or IQ is a minor factor, in which case how can it be used to gird prejudices as to the social station of Africans and their American descendants?