In the specific case of the United States, Christopher Dawes and Aaron C. Weinschenk, political scientists at N.Y.U. and the University of Wisconsin-Green Bay, write in their paper “On the genetic basis of political orientation” that “Twin studies show that political ideology is about 40 percent heritable.”

In separate work examining “the liberal-conservative ideological spectrum in world terms, communism to fascism not Democrats and Republicans,” Rose McDermott, a professor of international relations at Brown, found that “about 60 percent of overall liberal-conservative ideology is genetically influenced.”

Both McDermott and Weinschenk stressed the dangers of misinterpreting their data.

McDermott wrote by email that her conclusion “does not mean that 60 percent of ideology comes from genetic factors but rather that around 60 percent of differences between people can be attributed to genetic factors.”