In the study itself, there were two cohorts: a British cohort and a New Zealand cohort. In both cohorts, presence of the C allele (as either CC or CG) was associated with a hike in IQ by 6.4 and 7.0 points (from around 99-100 to around 106) in the two samples. But those without the C allele (GG) had mean IQs of 99.5 in Britain and 100.3 in New Zealand.

Incidentally, I plugged rs174575 into the ol' Hapmap, and it seems that the C allele has a frequency rate of 72% among Utah whites, 73% among Yorubans, 89% among the Chinese, and 90% among the Japanese.

Assuming these numbers are representative, universal breastfeeding alone would lead to a gap of 1.12 to 1.225 in IQs between East Asians and whites, favoring East Asians.

On the other hand, since whites and blacks have nearly the same C allele frequency (assuming, again that these numbers are representative of white and black populations), but whites breastfeed their babies at higher rates than blacks (60% vs. 30%, according to Steve), this is pretty solid evidence that increasing the percentage of black women who breastfeed their children will have a diminishing effect on the black white IQ gap.

Since I'm already blowing off work (damn you, Gene Expression!) I might as well do the calculations. Let's see... The 30% difference in breastfeeding is responsible for between 1.4 and 1.53 points in the black-white IQ gap! (I got these figures by multiplying the frequency rate of the C allele in Yorubans with the percentage difference in breastfeeding between blacks and whites with the effects of breastfeeding on the IQs of C allele carriers.)

Steve Sailer is vindicated!

Labels: Behavior Genetics, IQ