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The DNA of Politics
...Three political science professors—John Alford, Carolyn Funk, and John Hibbing—have studied political attitudes among a large number of twins in America and Australia. They measured the attitudes with something called the Wilson-Patterson Scale (I am not the Wilson after whom it was named), which asks whether a respondent agrees or disagrees with 28 words or phrases, such as “death penalty,” “school prayer,” “pacifism,” or “gay rights.” They then compared the similarity of the responses among identical twins with the similarity among fraternal twins. They found that, for all 28 taken together, the identical twins did indeed agree with each other more often than the fraternal ones did—and that genes accounted for about 40 percent of the difference between the two groups...

...Genes also influence how frequently we vote. Voting has always puzzled scholars: How is it rational to wait in line on a cold November afternoon when there is almost no chance that your ballot will make any difference? Apparently, people who vote often feel a strong sense of civic duty or like to express themselves. But who are these people? James Fowler, Laura Baker, and Christopher Dawes studied political participation in Los Angeles by comparing voting among identical and fraternal twins. Their conclusion: among registered voters, genetic factors explain about 60 percent of the difference between those who vote and those who do not...

...The gene-driven ideological split that Alford and his colleagues found may, in fact, be an underestimate, because men and women tend to marry people with whom they agree on big issues—assortative mating, as social scientists call it. Assortative mating means that the children of parents who agree on issues will be more likely to share whatever genes influence those beliefs. Thus, even children who are not identical twins will have a larger genetic basis for their views than if their parents married someone with whom they disagreed. Since we measure heritability by subtracting the similarity among fraternal twins from the similarity among identical ones, this difference may neglect genetic influences that already exist on fraternal twins. And if it does, it means that we are underestimating genetic influences on attitudes.

When we step back and look at American politics generally, genes may help us understand why, for countless decades, about 40 percent of all voters have supported conservative causes, about 40 percent have backed liberal ones, and the 20 percent in the middle have decided the elections. On a few occasions, the winning presidential candidate has won about 60 percent of the vote. But these days we call a 55 percent victory a “landslide.” It is hard to imagine a purely environmental force that would rule out a presidential election in which one candidate got 80 percent of the vote and his rival only 20 percent. Something deeper must be going on....