Does disease cause autocracy? New studies say reducing infection rates promotes liberalization.

• Author: Bailey, Ronald
• Position: Columns

GREATER WEALTH strongly correlates with property fights, the rule of law, education, the liberation of women, a free press, and social tolerance. The enduring puzzle for political scientists is how the social processes that produce freedom and wealth get started in the first place.

Many political theorists have linked liberal democracy to the rise of wealth and the establishment of a large middle class. "Growing resources are conducive to the rise of emancipative values that emphasize self-expression," write political scientists Ronald Inglehart of the University of Michigan and Christian Welzel of Jacobs University in their contribution to the 2009 book Democratization, "and these values are conducive to the collective actions that lead to democratization."

That same year, a group of researchers led by the Harvard economist Jeffrey Sachs noted in the Proceedings of the Royal Society B that a billion people live on less than a dollar per day and "are roughly as poor today as their ancestors were thousands of years ago." Sachs and his colleagues suggest that heavy disease burdens create persistent poverty traps from which poor people cannot extricate themselves. High disease rates lower their economic productivity so they can't afford to improve sanitation and medical care, which in turn leaves them vulnerable to more disease.

In a 2008 article for Biological Reviews, two University of New Mexico biologists buttressed the disease thesis with their "parasite hypothesis of democratization." The researchers, Randy Thornhill and Corey Fincher, argue that disease not only keeps people poor but makes them illiberal. Thornhill and Fincher tested this hypothesis "using publicly available data measuring democratization, collectivism, individualism, gender egalitarianism, property rights, sexual restrictiveness, and parasite prevalence across many countries of the world." The lower the disease burden, they found, the more likely a society is to be liberal.

Thornhill and Pincher argue that the risk of infectious disease affects elites' willingness to share power and resources, the general social acceptance of hierarchical authority, and the population's openness to innovation. Their central idea is that ethnocentrism and out-group avoidance function as a kind of behavioral immune system. Just as individuals have immune systems that fight pathogens, groups of people evolve with local parasites and develop some resistance to them. People who are not...