The underwhelming "liberal" Gene

I saw this from Jim Manzi on the liberal gene paper:

"As you may remember, I wrote a long piece for the magazine in 2008 that described why we should be very skeptical of assertions of causality that are derived from the kind of study that you reference. 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 you cite is an almost perfect illustration of this."



I appreciate the paleo-Fisherian (e.g., randomization is the only way to establish causality) viewpoint but there is utility to this sort of observational study and relating liberalism to biology gives you more than just rhetorical force. Neither the association of smoking and lung cancer nor the association of the BRCA gene and breast cancer was established via a randomized experiment in humans. The overwhelming weight of evidence came from observational studies AND in-vitro and animal studies, i.e., results from the wet lab.  In-vivo and in-vitro expreiments are amenable to randomization so the "totality" of the data convinced people, correctly I think, to stop smoking or, in the case of the BRCA gene, have prophylactic mastectomies.  A relation between a gene and behavior established in an observational study can be supported with evidence from the lab where causal relationships can be established.

  I doubt that will happen with the liberal gene though.  I read the paper and the results are underwhelming.  The paper fails to show that liberalism is related to a gene.  It purports to show a gene (the novelty seeking DRD4) by environment (number of friends in school) interaction is related to your adult ideology.   The actual magnitude of the interaction (p = .02) is unexciting. If you have two copies of the R7 allele  and you have four friends you become on average, 0.16 (on a five point scale) more liberal than a person with two friends. If y ou have no copies then friendship has no effect. It is weird that there is no main effect of genes or number of friends on liberalism and makes me doubt the results can be replicated. Their table 1 sums it up: there will be no selective breeding of NPR listeners any time soon.