Aristotle once noted, “Man is by nature a political animal.” What may be the first study to investigate this idea scientifically now controversially suggests that Aristotle may have been right—the desire to vote or abstain from politics might largely be hardwired into our biology.

When it comes to predicting who will vote, researchers have looked at “everything but the kitchen sink,” says political scientist James Fowler of the University of California, San Diego. Theorists speculate on factors such as age, gender, race, marital status, education, income, home ownership, political knowledgeability and church attendance. But studies indicate that each one exerts only a small effect.

Fowler notes that people who vote often do so even when they know their lone ballot will not change the outcome of an election. “It’s almost like voters are programmed to keep voting, even when their common sense tells them it is probably useless,” he states. At the same time, “many people never vote, no matter what. So I started to wonder if there was something very basic at the biological level.”

Fowler and his colleagues thus turned to identical and fraternal twins. If the decision to vote is based in part on genetics, they reasoned, identical twins should behave more alike than fraternal twins, because identical twins share all of their DNA, whereas fraternal twins share only half on average.

The researchers matched data from the Southern California Twin Registry with publicly accessible electronic voter registration and turnout records from Los Angeles County. Their analysis of voting histories for 326 identical and 196 fraternal twins suggests that genetics was responsible for 60 percent of differences in voting turnout between twin types, with the rest coming from environmental or other factors.

Fowler and his colleagues also investigated a larger, more nationally representative database from the National Longitudinal Study of Adolescent Health, or Add Health. This study not only asked if participants voted but also inquired about participation in other political activities, such as whether they contributed to campaigns or attended political rallies or marches. The researchers’ data on 442 identical and 364 fraternal Add Health twins indicate that genetics underlies 72 percent of differences in voting turnout and roughly 60 percent of differences in other political activity. Fowler, who presented the research at the American Political Science Association meeting in August, claims that preliminary results from the Twins Days festival in Twinsburg, Ohio, also support the findings.

Fowler adds that his team’s work does not suggest that genetics can determine whom people will vote for, only whether or not they are likely to vote. He also emphasizes that environment most likely plays a significant role in voting: “There is still a lot we can do to shape political behavior in spite of our genetic tendencies.”

If genes do in part control voting, a single gene is unlikely to be responsible—hundreds of genes are probably involved, suggests behavioral geneticist Robert Plomin of King’s College London. Fowler hypothesizes that because “we obviously did not vote in large-scale elections in the Pleistocene,” the drive to vote or participate in politics may be linked with genes underlying more ancient behaviors, such as innate dispositions toward cooperation. The search for any such genes in our primate relatives could help determine “whether we share the neurobiological underpinnings of cooperation or whether humans are unique in this respect,” Fowler adds.

Plomin states that “these findings are strong,” but in his analysis of the same data, he concludes that genetics was responsible for 40, and not 60, percent of differences in voting turnout between twin types. Forty percent is still “a lot,” he admits, and is also the average estimate of heritability seen in twin studies of personality, suggesting that voting is an example of a genetically influenced personality trait in general.

Behavioral neuroscientist Evan Balaban of McGill University, however, cautions that relying on twin studies as the sole evidence of links between genetics and behavior is a mistake. About two thirds of identical twins actually share the same bloodstream while fetuses, so greater similarities between twins could be attributable not only to sharing genes but “to sharing more similar levels of hormones and other compounds each fetus produces during development,” he explains. “So there is a pattern of similarity these researchers have documented that needs to be explained, but genetics is not the only explanation for it.”