...Breastfed children^ attain higher IQ scores than children not fed breast milk, presumably^ because of the fatty acids uniquely available in breast milk.^ Here we show that the association between breastfeeding and^ IQ is moderated by a genetic variant in FADS2, a gene involved^ in the genetic control of fatty acid pathways. We confirmed^ this gene-environment interaction in two birth cohorts,^ and we ruled out alternative explanations of the finding involving^ gene-exposure correlation, intrauterine growth, social^ class, and maternal cognitive ability, as well as maternal genotype^ effects on breastfeeding and breast milk. The finding shows^ that environmental exposures can be used to uncover novel candidate^ genes in complex phenotypes. It also shows that genes may work^ via the environment to shape the IQ, helping to close the nature^ versus nurture debate.
This reminds me a lot of the findings from a study of polymorphism on MAOA. One allele exhibited sensitivity toward environmental variation, while the other did not. This is a pretty simple norm of reaction, genotypes differently influenced by the same background environmental condition. Ars Technica has more detail. Check out the population differences of the twoSNPs they looked at on FADS2. Via Aziz.