Background

Posted above is a response I wrote to refute one specific assertion made by William Saletan in his series of three articles (1,2,3) which appeared on Slate.com between Nov. 18 and Nov. 20. Saletan's claim that a recent study linking breastfeeding, genes, and IQ can be used to show an innate genetic disadvantage for people of African descent is wrong.

Saletan's articles dealt with the subject of race and intelligence, and led to Saletan concluding that there is an innate intelligence gap between blacks and whites. Saletan's supporting evidence and methodology were quickly taken to task by the blogosphere as, at best, highly flawed and selective (some links collected below). The New York Times even picked up on the story here. So far though, no one (as far as I can tell) has addressed the IQ-breastfeeding claim. (Continue Reading...)

The blogs were right. In the end it was Stephen Metcalf at Slate who wrote the best point-by-point refutation of Saletan's arguments. The highlights include:

--Saletan heavily realized on the research of James Rushton, the current director of the Pioneer Fund, which was founded in 1937 to promote the principles of Nazi eugenics (really: see here and here), and has been steadily promoting racist "research" ever since--which did cause Saletan to write an apology once this was pointed out to him.

--Saletan implies that because intelligence is hereditable from person to person (to some degree), and that because there is an IQ difference across groups, then therefore there's an inherited difference between the groups. This does not follow at all: for example, in a malnourished population, height is still strongly hereditable (taller parents have taller children, shorter parents have shorter children), but once you feed everyone, the average height goes up. (Yes, I am stealing this example from Stephen Jay Gould).

--Saletan discounts studies that show no IQ difference between blacks and whites for irrelevant reasons. For example, he wrongly discounts a study showing no difference in the IQs of children fathered by black and white American soldiers in Germany after WWII.

--Saletan ignores or underplays evidence that the IQ gap in the U.S. between blacks and whites is closing. (IQ scores in the developed world have been rising steadily since testing began).

However, in all this, one assertion of Saletan's has remained unchallenged, so far as I can tell. It's his claim that data from a study linking the well-known boost in IQ scores cause by breastfeeding to a particular gene can be used to show that blacks tend to have this form of the gene at lesser frequencies, and are thus cognitively disadvantaged. Here's the relevant passage from his third article:

As my colleague Emily Bazelon explains, a new study shows that while most babies gain an average of seven IQ points from breast-feeding, some babies gain nothing from it and end up at a four-point disadvantage because they lack a crucial gene.

The study's authors claim it "shows that genes may work via the environment to shape the IQ, helping to close the nature versus nurture debate." That's true if you have the gene. But if you don't, nurture can't help you. And guess what? According to the International Hapmap Project, 2.2 percent of the project's Chinese-Japanese population samples, 5 percent of its European-American samples, and 10 percent of its Nigerian samples lack the gene. The Africans are twice as likely as the Americans, and four times as likely as the Asians, to start life with a four-point IQ deficit out of sheer genetic misfortune.

Don't tell me those Nigerian babies aren't cognitively disadvantaged. Don't tell me it isn't genetic.

I think that this specific claim has not received attention for a combination of several reasons: it was at the end of the last article in the series, and Saletan's arguments were mostly laid out in the first two articles; it is not the result of work by obvious racists or funded by hateful organizations, like many of his other claims, but is instead based on legitimate, interesting work by respected scientists; it is in an unfamiliar field (genetics); and it is hard to figure out where Saletan is getting his number from. Yet it is just as wrong as his other arguments, as I hope I have shown. And, I believe, it is no less important to show that it is wrong. Genetics, sadly, will probably be the next frontier for Pioneer-funded research and its like, and it's important to be aware that claims from genetics can not simply accepted at face value.


Some Blog Reactions To Saletan's Articles:
Brad Delong, Three-Toed Sloth: 1, 2, Talking Points Memo, Matthew Yglesias: 1, 2