Tag Archives: slate

Genetic and Environmental Causes of Human Diversity

Just because a side in an argument uses bad arguments doesn’t mean it’s wrong. By far, the least logic and most emotional rhetoric I have ever seen was in the newsgroup talk.origins in the late 1990s, where evolutionists were bufeddled and angered by the repleis of the creationists. That doesn’t mean that descent with modification by natural selection is a wrong theory. It means that the truth was weaker in its rhetoric than the false.

With that said, Stephen Metcalf’s “Dissecting the IQ Debate: A Response to William Saletan’s Series on Race and IQ” (hat-tip to The Corner and South Dakota Politics) is awful.

After a lengthy ad hominem attack, Metcalf begins addressing evidence for racial differences in IQ.


Much of Saletan’s précis of the rest of the research surveyed in “Thirty Years of Research Into Race Differences on Cognitive Abilities” is highly questionable. His takeaway regarding the “admixture” studies is precisely the opposite of what an American Psychological Association task force concluded the studies show—that more “European” blood in a black American does not make him smarter.

Pay attention here. Metcalf attacks Saletan for citing a peer-reviewed journal article, when a politically selected task force disagreed with its conclusions. No one denies the factual claims of the article: that European admixture positively correlates with general intelligence among African-Americans. Indeed, that alone is not evidence of innate racial differences. But the correlation between miscegenation and g in the population does not go away even when corrected for other variables.


Saletan points up the problems with a favorite study of the environmentalists, into the IQ outcomes of children fathered by foreign soldiers and raised by (white) German mothers. This study showed that kids with African fathers scored the same as those with white fathers. But, Saletan says, it suffers from a fatal flaw: Blacks in the military had been screened for IQ. Saletan concludes, “Even environmentalists (scholars who advocate nongenetic explanations) concede that this filter radically distorted the numbers.” But this is flatly untrue. The two most prominent environmentalists, Richard Nisbett and James Flynn, have dismissed this very objection. Both have pointed out that white soldiers were also screened, and so had higher IQs than the general white population.

This regards a study that finds Germans with African-American fathers have an IQ about that of the German population. This might be explained by the fact that the military screens for IQ, rejecting a disproportionately high number of African-Americans for that reason. The counter-argument that European-Americans were also screened is besides the point: the US Army in WWII did not engage in affirmative action. The minimum IQ level for blacks was the same as the minimum IQ level for whites.


Saletan uses a sheer volume of statistics to create an aura of gathering unanimity, but many of his statistics have been taken at face value. To take one example: Saletan casually countenances the assertion that the mean IQ of sub-Saharan Africa is 70. The number arrives to us via a man named Richard Lynn. Lynn is the author of the 1996 volume “Dysgenics: Genetic Deterioration in Modern Populations.” In “historical societies,” Lynn wrote, “illegitimate children, born predominantly to parents with low intelligence and weak character, suffered high mortality.” Until the scourge of modern medicine, such culling assured the expulsion of weaklings from the gene pool, while the “operation of positive natural selection” ensured the “reproductive fitness of the leaders and of the upper and middle classes.” The instrument Lynn used to apprehend these depressed IQ scores is a supposedly culturally unbiased exam called Raven’s Progressive Matrices. “To use an instrument developed in the West on semi and possibly illiterate people is a fool’s errand,” says Nisbett, a Distinguished University Professor at the University of Michigan who studies cognition and social psychology. “Then they use the results to say that half the people in Africa are mentally retarded. It’s laughable.”

Here, the web can help out. The table in Flynn’s book is available online. Some tests use the Raven tool, others use other tool.

The next paragraph again relies on the political summary of an APA body, and thus is unoworthy of comment.


Furthermore, the APA task force lays out—finally!—the real heart of the conflict. To understand what is really being fought over when we fight over the IQ gap between blacks and whites, its authors explain, you must think through an analogy. Imagine two wheat fields. Now imagine two genetically identical sets of seeds. (The analogy was first made famous by the Harvard evolutionary biologist and geneticist Richard Lewontin.) Now imagine each field is planted with these two identical seed stocks. Field No. 1 is given the best possible inputs: sunshine intensity, rain, soil nitrates, etc. Field No. 2 is given much less of all of the above. Within each field, inputs are kept uniform. Inevitably, the first field grows a healthier supply of grain than the second. But here is the rub: Within each field, the variation in outcomes is entirely hereditary. Between the two fields, the variation in outcomes in entirely environmental.

An excellent analogy. Using it, one would expect that environment differences, such as parent’s income, drown out genetic differences, such as race.

But that is just not so. From the original Saletan article:

My first reaction, looking at this pattern, was that if the highest-scoring blacks are those who have lighter skin or live in whiter countries, the reason must be their high socioeconomic status relative to other blacks. But then you have to explain why, on the SAT, white kids from households with annual incomes of $20,000 to $30,000 easily outscore black kids from households with annual incomes of $80,000 to $100,000. You also have to explain why, on IQ tests, white kids of parents with low incomes ­and low IQs outscore black kids of parents with high incomes and high IQs. Or why Inuits and Native Americans outscore American blacks.

But Metcalf makes it clear that he believes that living in a good neighborhood, in a good home, with high-income parents, it itself drowned out by “the legacy of American racism.”

In the absence of some startling new evidence, the crux of the issue turns out to be this: Do you believe the legacy of American racism, in all its complexity, can explain depressed black IQ scores, even when controlling for all other factors, including socioeconomic status? Is the black experience, in other words, so unique as to constitute, for nearly all black Americans, a separate wheat field? If you say yes, then good news: You believe (along with the most prominent environmentalists) that the black-white IQ gap will close in the next 50 or so years. If you think no, then bad news: You believe, with the most prominent hereditarians, that blacks as a group must resign themselves to higher rates of poverty, unemployment, divorce, and violent criminality purely as a matter of genetic fate.

Indeed. This is the first good point that Metcalf makes in the entire article.

Such a “legacy of racism” must be indirect, as it does not seem to harm either Afro-Carribeans or immigrants from Africa.

More likely, such a legacy of racism is the profoundly broken African-American culture. This, and not “racism” as its commonly conceived, is the explanation that James Flynn and other environmentalists look for. And perhaps they are right.

But there is another explanation: as immigrant populations, both Afro-Carribeans and immigrants from Africa are self-selected: moving to a new country is dangerous, especially when it means weakening the strong family ties back home. It requires a special something — a something that can include general intelligence — to go through the time-consuming and dangerous immigration process. Perhaps the reason that black immigrants from Africa and the Carribean do better than African Americans on so many measures is precisely genetic.