Saturday, November 29, 2008

Born that way?

Before I leave behind the special issue of Science on the Genetics of Behavior (November 7), let me take note of one more article, "Biology, Politics, and the Emerging Science of Human Nature," by James H. Fowler and Darren Schreiber. Do genes affect the way we vote?

A twin-based study published in the American Political Science Review in 2005 suggested that liberal and conservative tendencies are heritable. Most evidence, however, shows that choice of a political party is primarily determined by parental socialization, that is, nurture. One might have guessed as much from a red-state-blue-state political map.

What does seem to be strongly heritable is political activism.

Here is a diagram from Fowler and Schreiber's article, showing the results of three twin studies on political participation (click to enlarge). The vertices of the diagrams represent respectively shared genes, shared environment, and unshared environment; that is, the studies considered identical and non-identical twins, and twins raised together and raised apart. The correlations suggest that genetics and environment both play a role in political activism, with genes being the dominant factor.

The next step is to find the genes that determine our level of political engagement. Genes that affect the regulation of neurotransmitters have been most closely scrutinized. Three genes mentioned by Fowler and Schreiber -- MAOA (monoamine oxidase A), 5HTT (serotonin transporter) and DRD2 (dopamine receptor) -- have been linked to political behavior.

Aristotle said that we are by nature political animals. We are surely animals. Some of us are apparently more political than others.