You Are a Republican Because of Your Genes. Or in Spite of Them.

While we all pride ourselves on having developed our political identity after a lengthy period of thoughtful contemplation, it turns out that it's at least 56 percent thanks to genetics.

While we all pride ourselves on having developed our political identity after a lengthy period of thoughtful contemplation, it turns out that it's at least 56 percent thanks to genetics. At least, that's what a new study outlined by Pew Research suggests, complete with some substantial caveats.

Conducted by nine psychologists (including one associated with Pew), the research looks at the political beliefs of sets of twins registered with the Minnesota Twin Registry. While fraternal twins share an upbringing, identical twins share both upbringing and genes. As Pew explains, "if identical twins are significantly more alike in their views than fraternal twins, that’s strong evidence pointing to a genetic basis for the attitude."

The findings, in short:

They found that somewhat more than half of the difference in self-identified political ideology (56%) is explained by genetic factors. The remainder was explained by unique factors affecting one twin and not the other. A second measure of ideology based on 27 questions produced a similar result (genes appeared to explain 58% of the difference between individuals).

A link between political belief and genes isn't a new idea; CNN talked about it five years ago, and The Economist outlined existing studies just last year. According to one meta-analysis cited by the magazine, identical twins were 20 percent more likely to share political beliefs than fraternal ones. (Note: We decided to forego any jokes about the movie Twins, starring Republican Arnold Schwarzenegger and Democrat Danny DeVito, because does anyone even remember that movie anymore? No, probably not.)

The most recent study tested other things, too. The image at right shows how likely various attitudes and traits are likely to be linked to genetics. The tendency to be extroverted is strongly linked to genetics, for example, while neuroticism is not. (Good news for Ronan Farrow, maybe.) Pew explains the findings on "egalitarianism":

Twins were asked how much they agreed or disagreed with five statements, including “If wealth were more equal in this country we would have many fewer problems,” and “We have gone too far in pushing equality in this country.” Again they found that half of the variance appeared to be explained by genetic factors.

Appropriately enough, at a 50/50 split.

It's the political findings that are likely to provoke the most response, in large part because they feel more personal. Both Democrats and Republicans are at times accused by their opponents of failing to be thoughtful in making political decisions, which is an argument reinforced by the suggestion that you're more likely than not to have inherited your belief system.

If you'd like to counter that argument, some good news. As The Economist report put it, researchers suggest only that "genes assist in deciding which opinions an individual will find it most attractive to cleave to" — not that they're definitive. The metholodogy here introduces some pause, as Pew notes; the sample set, coming as it does from Minnesota, is not terribly diverse demographically.

And, of course, there's the plain old-fashioned math. If 56 percent of your political leanings stem from genetics, 44 percent come from your very own research/studious attention to political debate/interest in learning the details of public policy options. Because obviously that's what we do.