Liberal Genes?

Jim Manzi debunks a misleading study:

Jonah, Goldberg and John Derbyshire are having an interesting exchange at The Corner on whether researchers have a found a gene that, under certain environmental conditions, predisposes individuals to liberal politics.

I wrote a long piece (gated) for National Review in 2008 that described why we should be very skeptical of assertions of causality that are derived from gene association studies. The basic reason is that, while these kinds of studies have remarkable rhetorical force because their purported  subject is biology, if you look under the skin at the bones of the analysis, the core method is traditional social science. The article under consideration is an almost perfect illustration of this.