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In my previous post, I discuss the “50-0-50 rule” of behavior genetics, how genes and unshared environment each account for roughly half of the variance in adult personality and behavior, and how the shared environment of siblings has virtually no effect on how children turn out. One area where the 50-0-50 rule plays out perfectly is partisan attachment, whether you identify with your political party strongly or weakly.
The political scientist who has pioneered the behavior genetic approach to politics more than any other is James H. Fowler of the University of California - San Diego, who is one of the young rising stars of political science. Among his numerous other significant contributions to political science, for example, Fowler has managed to isolate just two genes (MAOA and 5HTT) that significantly influence voter turnout. In other words, whether you turn out to vote on any given election is strongly influenced by your genes.
In the area of partisan attachment (how strongly you identify with your political party), the behavior genetic models of Fowler and colleagues show that it roughly follows the 50-0-50 rule, or, more precisely, 46-0-54: 46% of the variance in partisan attachment is heritable (determined by genes), 0% is due to shared environment, and 54% is due to unshared environment. It is important not to attach too much significance to the precise figures in the breakdown, because it’s likely to vary slightly depending upon which samples and populations the researchers use.
In fact, in an article forthcoming in Political Science Quarterly, Peter K. Hatemi and colleagues estimate that the breakdown is precisely 50-0-50. Their models, for both men and women, show that exactly 50% of the variance in partisan intensity is heritable, exactly 0% is attributable to shared environment, and exactly 50% is due to unshared environment. Once again, the important point is that it is roughly 50-0-50 for many adult personality and behavioral traits.
Interestingly, the same paper by Hatemi et al. shows that, while partisan intensity (how strongly you identify with your political party) is strongly influenced by genes, party identification (which party you identify with) is not at all heritable; instead, party identification appears to be largely due to shared environment. In other words, you are a Democrat (as opposed to a Republican) because your parents taught you to be a Democrat, but you are a strong Democrat (as opposed to a weak Democrat) because of your genes. To put it differently, the strong heritability of partisan intensity, but not party identification, means that a strong Democrat may be more likely to beget a strong Republican than to beget a weak Democrat.
To complicate matters, while whether you are a Democrat or a Republican does not appear to be heritable, whether you are liberal or conservative is largely genetic. A ground-breaking paper, published in the premier journal in political science American Political Science Review in 2005, by John R. Alford, Carolyn L. Funk, and John R. Hibbing, shows that political orientations on the liberal-conservative scale (measured by respondents’ attitudes on a wide range of 28 different issues from X-rated movies and gay rights to nuclear power and foreign aid) are partly heritable, although the breakdown somewhat deviates from the 50-0-50 rule. Instead, their behavior genetic analysis of an American sample shows it to be 43-22-35: 43% of the variance in political (liberal-conservative) attitude is determined by genes, 22% by shared environment, and 35% by unshared environment. While the effect of shared environment in their analysis is not 0, it is still the weakest determinant of political attitude, and genes are still most important, twice as important as parental socialization.
The pioneering work of James H. Fowler and others in a (yet) small contingent of behavior genetic political scientists (I’m not sure if there is an established name for their approach yet in political science) demonstrates the importance of genetic influences for a whole host of personality and behavioral measures, including political attitude and partisan strength.
P.S. James now tells me that his favored name for the field that he is helping to create is “genopolitics.” I like it and hope the name will spread.
