Race, Genes, and Intelligence

William Saletan, slate.com, November 18, 2007

Part 1: Liberal Creationism

November 18, 2007

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights . . .

—Declaration of Independence

Last month, James Watson, the legendary biologist, was condemned and forced into retirement after claiming that African intelligence wasn’t “the same as ours.” “Racist, vicious and unsupported by science,” said the Federation of American Scientists. “Utterly unsupported by scientific evidence,” declared the U.S. government’s supervisor of genetic research. The New York Times told readers that when Watson implied “that black Africans are less intelligent than whites, he hadn’t a scientific leg to stand on.”

I wish these assurances were true. They aren’t. Tests do show an IQ deficit, not just for Africans relative to Europeans, but for Europeans relative to Asians. Economic and cultural theories have failed to explain most of the pattern, and there’s strong preliminary evidence that part of it is genetic. It’s time to prepare for the possibility that equality of intelligence, in the sense of racial averages on tests, will turn out not to be true.


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.


I’m for reconciliation. Later this week, I’ll make that case. But if you choose to fight the evidence, here’s what you’re up against. 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.


We don’t like to think IQ is mostly inherited. But we’ve all known families who are smarter than others. Twin and sibling studies, which can sort genetic from environmental factors, suggest more than half the variation in IQ scores is genetic. A task force report from the American Psychological Association indicates it might be even higher. The report doesn’t conclude that genes explain racial gaps in IQ. But the tests on which racial gaps are biggest happen to be the tests on which genes, as measured by comparative sibling performance, exert the biggest influence.

How could genes cause an IQ advantage? The simplest pathway is head size. I thought head measurement had been discredited as Eurocentric pseudoscience. I was wrong. In fact, it’s been bolstered by MRI. On average, Asian-American kids have bigger brains than white American kids, who in turn have bigger brains than black American kids. This is true even though the order of body size and weight runs in the other direction. The pattern holds true throughout the world and persists at death, as measured by brain weight.

According to twin studies, 50 percent to 90 percent of variation in head size and brain volume is genetic. And when it comes to IQ, size matters. The old science of head measurements found a 20 percent correlation of head size with IQ. The new science of MRI finds at least a 40 percent correlation of brain size with IQ. One analysis calculates that brain size could easily account for five points of the black-white IQ gap.

I know, it sounds crazy. But if you approach the data from other directions, you get the same results. The more black and white scores differ on a test, the more performance on that test correlates with head size and “g,” a measure of the test’s emphasis on general intelligence. You can debate the reality of g, but you can’t debate the reality of head size. And when you compare black and white kids who score the same on IQ tests, their average difference in head circumference is zero.

Scientists have already identified genes that influence brain size and vary by continent. Whether these play a role in racial IQ gaps, nobody knows. But we should welcome this research, because any genetic hypothesis about intelligence ought to be clarified and tested.

Critics think IQ tests are relative—i.e., they measure fitness for success in our society, not in other societies. “In a hunter-gatherer society, IQ will still be important, but if a hunter cannot shoot straight, IQ will not bring food to the table,” argues psychologist Robert Sternberg. “In a warrior society . . . physical prowess may be equally necessary to stay alive.” It’s a good point, but it bolsters the case for a genetic theory. Nature isn’t stupid. If Africans, Asians, and Europeans evolved different genes, the reason is that their respective genes were suited to their respective environments.

In fact, there’s a mountain of evidence that differential evolution has left each population with a balance of traits that could be advantageous or disadvantageous, depending on circumstances. The list of differences is long and intricate. On average, compared with whites, blacks mature more quickly in the womb, are born earlier, and develop teeth, strength, and dexterity earlier. They sit, crawl, walk, and dress themselves earlier. They reach sexual maturity faster, and they have better eyesight. On each of these measures, East Asians lag whites and blacks. In exchange, East Asians get longer lives and bigger brains.

{snip} Genetic advantages, in other words, are culturally created.

Not that that’s much consolation if you’re stuck in the 21st century with a low IQ. Tomorrow we’ll look at some of the arguments against the genetic theory.

Part 2: Environmental Impact

November 19, 2007

Yesterday we looked at evidence for a genetic theory of racial differences in IQ. Today let’s look at some of the arguments against it. Again, I’m drawing heavily on a recent exchange of papers published by the American Psychological Association.

One objection is that IQ tests are racially biased. This is true in the broadest sense: On average, African and Asian kids have different advantages, and IQ tests focus on the things at which more Asian kids have the edge. But in the narrower sense of testing abilities that pay off in the modern world, IQ tests do their job. They accurately predict the outcomes of black and white kids at finishing high school, staying employed, and avoiding poverty, welfare, or jail. They also accurately predict grades and job performance in modern Africa. The SAT, GRE, and tests in the private sector and the armed forces corroborate the racial patterns on IQ tests. Kids of different backgrounds find the same questions easy or hard. Nor do tests always favor a country’s ethnic majority. In Malaysia, Chinese and Indian minorities outscore Malays.

If the tests aren’t racist, some critics argue, then society is. That’s true, in the sense that racism persists. But that alone can’t account for the patterns in IQ scores. Why do blacks in the white-dominated United States score 15 points higher than blacks in black-dominated African countries, including countries that have been free of colonial rule for half a century? And why do Asian-Americans outscore white Americans?

Another common critique is that race is a fuzzy concept. By various estimates, 20 percent to 30 percent of the genes in “black” Americans actually came from Europe. Again, it’s a good point, but it bolsters the case for a genetic explanation. Black Americans, like “colored” South Africans, score halfway between South African blacks and whites on IQ tests. The lowest black IQ averages in the United States show up in the South, where the rate of genetic blending is lowest. There’s even some biological evidence: a correlation between racial “admixture” and brain weight. Reading about studies of “admixture” is pretty nauseating. But the nausea doesn’t make the studies go away.


The current favorite alternative to a genetic explanation is that black kids grow up in a less intellectually supportive culture. This is a testament to how far the race discussion has shifted to the right. Twenty years ago, conservatives were blaming culture, while liberals blamed racism and poverty. Now liberals are blaming culture because the emerging alternative, genetics, is even more repellent.

The best way to assess the effects of culture and socioeconomic status is to look at trans-racial adoptions, which combine one race’s genes with another’s environment. Among Asian-American kids, biological norms seem to prevail. In one study, kids adopted from Southeast Asia, half of whom had been hospitalized for malnutrition, outscored the U.S. IQ average by 20 points. In another study, kids adopted from Korea outscored the U.S. average by two to 12 points, depending on their degree of malnutrition. In a third study, Korean kids adopted in Belgium outscored the Belgian average by at least 10 points, regardless of their adoptive parents’ socioeconomic status.

Studies of African-American kids are less clear. One looked at children adopted into white upper-middle class families in Minnesota. The new environment apparently helped: On average, the kids exceeded the IQ norms for their respective populations. However, it didn’t wipe out racial differences. Adopted kids with two white biological parents slightly outscored kids with one black biological parent, who in turn significantly outscored kids with two black biological parents. The most plausible environmental explanation for this discrepancy is that the half-black kids (in terms of their number of black biological parents) were treated better than the all-black kids. But the study shot down that theory. Twelve of the half-black kids were mistakenly thought by their adoptive parents to be all-black. That made no difference. They scored as well as the other half-black kids.


Each camp points out flaws in the other’s studies, and the debate is far from over. But when you boil down the studies, they suggest three patterns. One, better environments produce better results. Two, moms appear to make a difference, environmentally and biologically. (Their biological influence could be hormonal or nutritional rather than genetic.) Three, underneath those factors, a racial gap persists. One problem with most of the adoption studies is that as a general rule, genetic differences in IQ tend to firm up in adolescence. And in the only study that persisted to that point (the one in Minnesota), kids scored on average according to how many of their biological parents were black.

The best argument against genetics isn’t in these studies. It’s in data that show shrinkage of the black-white IQ gap over time. From these trends, environmentalists conclude that the gap is closing to zero. Hereditarians read the data differently. They agree that the gap closed fractionally in the middle decades of the 20th century, but they argue that scores in the last two to three decades show no improvement.


When I look at all the data, studies, and arguments, I see a prima facie case for partial genetic influence. I don’t see conclusive evidence either way in the adoption studies. I don’t see closure of the racial IQ gap to single digits. And I see too much data that can’t be reconciled with the surge or explained by current environmental theories. I hope the surge surprises me. But in case it doesn’t, I want to start thinking about how to be an egalitarian in an age of genetic difference, even between races. More on that tomorrow.


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