Polish voters will head to the polls on June 20 to elect a replacement for the late President Lech Kaczynski, who died in a plane crash two weeks ago. Kaczynski's identical twin brother, Jaroslaw, may contest the election. Are Jaroslaw and Lech any more likely to agree with each other on political matters than George and Jeb Bush or Jack and Teddy Kennedy?
Yes, but no one really knows why. In recent years, researchers have posed a series of hot-button political questions to pairs of identical and fraternal twins. The first major study (PDF) of this kind, published in 2005, asked twins for their positions on issues like foreign aid, death penalty, and abortion. Responses from identical twins were more correlated than those from fraternal twins on every issue. School prayer and property taxes were singled out by the researchers as being the most strongly influenced by genetics. When responses were aggregated and reduced to either a conservative or liberal worldview, the authors concluded that genetics could explain 43 percent of someone's political outlook.
While most observers agree that identical twins are more likely to share a political identity, many have contested the notion that genetics are the cause. Studies of this kind are based on the assumption that monozygotic (identical) twins share the same genes and the same environment, while dizygotic (fraternal) twins have only the latter in common. But identical twins are not always treated the same way as dizygotic twins. They may be dressed the same way by their parents, made to sleep in the same bedroom, or given rhyming names. They're also likely to spend more time together and to be confused for each other by family and friends. At the same time, monozygotic twins aren't really genetically identical (PDF) in the first place. So their convergent worldviews might be due to environmental, and not genetic, factors.
Polish voters shouldn't make any assumptions. Countless people have genetically cloned their favorite animals, expecting that they will get a personality clone. It often doesn't work. One family copied their docile celebrity bull, who had appeared in photographs with everyone from Mother Theresa to Roger Clemens. The clone gored his master repeatedly, dislocating his shoulder, ripping open his scrotum, and fracturing his spine. The owners refused put the beast down, hoping he would mature into his twin's disposition. He never did.
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Explainer thanks John R. Alford of Rice University, Evan Charney of Duke University, John R. Hibbing of the University of Nebraska-Lincoln, and Elizabeth Suhay of Lafayette College.