“Are Political Orientations Genetically Transmitted?” by John R. Alford, Carolyn L. Funk, and John R. Hibbing, in American Political Science Review (May 2005), George Washington Univ., Dept. of Political Science, 1922 F St., N.W., Ste. 401A, Washington, D.C. 20052.

Most political scientists don’t even want to think about this, but is it possible that conservatives and liberals are born that way? It’s not quite that simple, say political scientists Alford, Funk, and Hibbing, but evidence from studies of twins indicates that genes play a strong role in shaping individuals’ basic political outlooks.

The authors analyzed the responses of nearly 4,500 pairs of twins when they were presented with 28 short social or political terms, such as school prayer and Republicans, and asked to “agree” or “disagree” with them. The authors then categorized the answers as “liberal” or “conservative.” They found a much higher level of agreement among the identical twins in the survey than among the fraternal twins (who share only 50 percent of their genetic material). Comparing the differences, the authors calculated that genes account for 43 percent of the “variability” between the two groups, while shared environment accounts for only 22 percent. To put it in more concrete terms: The political ideology of individuals is, on average, about half determined by genes.

The authors point out that this makes a great deal of sense if one considers that social scientists have been trying fruitlessly for decades to tease out what environmental factors influence political ideology. Opinionated fathers? Long political discussions around the dinner table? Permissive child-rearing? All of these, and many other factors, have been measured and found lacking in explanatory power.

There is no single “liberal” or “conservative” gene, say Alford, Funk, and Hibbing (of Rice University, Virginia Commonwealth University, and the University of Nebraska, respectively). Instead, many genes, interacting in various ways, are involved in influencing people’s political outlooks. But the authors speculate that these interactions tend to tilt people toward one of two basic types of mindsets: absolutist, with a taste for order, clear rules, and “in-group unity,” and contextualist, with an aversion to hierarchy and unbending rules and a high degree of empathy. Yes, the authors say, that’s in effect the same as conservative and liberal.

Still, individuals do seem to make some important political decisions with very little input from their genes. The authors found that heredity has little effect on political party affiliation. Parental views probably count for much more there, as they do in decisions to identify with a particular church.

If all of this is true, one of the interesting questions is, why would evolution care about politics? What is the evolutionary advantage of political diversity? There are several possible explanations, but most appealing to the authors is the thought that diverse approaches keep human society on its toes and ready to adapt, and therefore healthier.