In their book “Predisposed: Liberals, Conservatives, and the Biology of Political Differences,” Hibbing, Kevin B. Smith, of the University of Nebraska, and John R. Alford, of Rice, argue that liberalism is “an evolutionary luxury” that can emerge in people when “negative stimuli becoming less prevalent and less deadly,” or, as Hibbing put it in an email, “when daily threats to life and limb posed by other human beings have diminished.”

Conversely, they write, if the environment shifts back to a “threat-filled atmosphere,” then “positive selection for conservative orientations would reappear.”

Let’s take a look at one of the core divisions between liberals and conservatives: the causes of poverty. The right tends to blame individual failings while the left tends to place the onus on economic and political forces. The accompanying chart, created from 2019 Voter Study Group data by Zach Goldberg, a doctoral candidate in political science at Georgia State, shows the difference.