Tuesday, November 06, 2007

Nature via Nurture: IQ via breastfeeding

The Nature vs Nurture debate is now old-fashioned and instead enlightened people like Malcom Gladwell have been reformulating it as Nature via Nurture where, for genes to make their impact, appropriate environmental agents have to be present. Ed Yong of the excellent Not Exactly rocket Science blog, blogs about a recent study that shows that IQ differences (of up to 7 points) in people with two different variants of a gene, FADS2, can be accomplished under the environmental conditions of breastfeeding. Thus, the gene, which is instrumental in metabolism of some fatty acids, leads to increase in IQ points, but only if the babies are breast-fed. The link seems that this gene is necessary to metabolize some of the the fatty acids present in mother's milk.

I especially like the implications for genetics, that Yong derives from this study.


The study also has big implications for gene-hunters. The usual tactic for finding genes linked to physical traits or behaviours is to scan the entire genome for genes that have direct and prominent effects.

But if the team had used this tactic, they would never have billed FADS2 as an IQ-related gene (I’m avoiding using the phrase “a gene for IQ” because it’s trite and misleading). That’s because there are no significant differences between the IQ scores of people with the two FADS2 variants if you take breastfeeding out of the equation. The upshot is that geneticists can look to the environment for important clues when looking for genes that affect human behaviour and health.

For the foreseeable future, it looks like the dichotomy of nature and nurture is dying. It’s proving to be far more interesting to look at how the two interact, and good examples are springing up fast.

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