Scientists and laypeople alike have historically attributed political beliefs to upbringing and surroundings, yet recent research shows that our political inclinations have a large genetic component.

The largest recent study of political beliefs, published in 2014 in Behavior Genetics, looked at a sample of more than 12,000 twin pairs from five countries, including the U.S. Some were identical and some fraternal; all were raised together. The study reveals that the development of political attitudes depends, on average, about 60 percent on the environment in which we grow up and live and 40 percent on our genes.

“We inherit some part of how we process information, how we see the world and how we perceive threats—and these are expressed in a modern society as political attitudes,” explains Peter Hatemi, who is a genetic epidemiologist at the University of Sydney and lead author of the study.

The genes involved in such complex traits are difficult to pinpoint because they tend to be involved in a huge number of bodily and cognitive processes that each play a minuscule role in shaping our political attitudes. Yet a study published in 2015 in the Proceedings of the Royal Society B managed to do just that, showing that genes encoding certain receptors for the neurotransmitter dopamine are associated with where we fall on the liberal-conservative axis. Among women who were highly liberal, 62 percent were carriers of certain receptor genotypes that have previously been associated with such traits as extroversion and novelty seeking. Meanwhile, among highly conservative women, the proportion was only 37.5 percent.

“Perhaps high-novelty seekers are more willing to entertain the idea of change, including in the political sphere,” says the study's lead author, Richard Ebstein, a molecular geneticist at the National University of Singapore. He admits, however, that the dopamine genes are undoubtedly just a small part of the story of how we inherit political attitudes, with hundreds of other genes equally involved.

These genetic findings are in line with the many psychological studies that have suggested that political attitudes are related to personality traits. Openness to experience, for example, predicts a liberal ideology; conscientiousness often goes with a conservative stance. Yet the evidence suggests that political attitudes are not entirely explained by personality; the two are more likely independently rooted in what Hatemi calls a “common psychological architecture.” Hatemi and his colleague Brad Verhulst, a political scientist at Pennsylvania State University, published a study in 2015 in PLOS ONE showing that changes in personality over a 10-year period do not predict changes in political attitudes.

Ultimately these early genetic results lend weight to the hypothesis that political beliefs may depend heavily on very basic processes in the brain—our ancient instincts to avoid danger and filth, which we experience as fear and disgust. Psychologists at the University of Warwick in England recently proposed a theory along these lines in a January paper published in Topics in Cognitive Science.

Using a computer simulation, they showed that when our ancestors met groups of strangers, they had to make choices among potential opportunities, such as new mates and trade, and risks, such as exposure to new pathogens. In areas with high levels of infections, their model showed that the driving force of evolution was fear of outsiders, conformity and ethnocentrism—things that in modern times we would call social conservatism.