A psychological link between disease and gender equality

Enlarge / In the movie Children of Men, declining public health leads to extreme social inequality.

Levels of disease in the environment may be linked to gains in women's political power. That's the finding of two psychologists who pored over six decades of data, looking at connections between ecological stressors and gender equality. Arizona State - Tempe's Michael E. W. Varnum and University of Waterloo, Canada's Igor Grossmann found that declining infectious disease rates in the US were strongly correlated with a rise in gender equality. The big question is why. Writing in Nature Human Behavior, the researchers say the trend can be partly explained by looking at how pathogens "cue people to adopt faster life strategies."

Varnum and Grossman's study was inspired by the field of behavioral ecology, where scientists explore how the physical environment affects animal behavior. Obviously, social equality among humans is affected by political events such as the passage of Title IX and anti-discrimination laws. But the researchers were curious about whether environmental factors might also have an impact on whether we build societies that are more egalitarian or more authoritarian. To get an answer, Varnum and Grossmann narrowed their focus to looking strictly at gender equality between the years 1951 and 2013 in the US and the UK. They explain that they created "an index of gender equality using data on indicators of political representation (the number of women in Congress), wage inequality (male:female wage ratio based on data from the US Women’s Bureau and the National Committee on Equal Pay), linguistic representation in cultural products (use of male versus female pronouns in published books) and sexist work attitudes (percentage of respondents in Gallup polls preferring a male boss)."

The decline in gender inequality was preceded by lower levels of infectious disease in the US and the UK.

They stacked this data up against changes in four environmental problems that affect humanity: infectious disease, resource scarcity, warfare, and climatic stress. Of the four, only infectious disease could predict levels of gender equality. But the effect was striking. As levels of infectious disease dropped, Varnum and Grossmann could see a similar drop in gender inequality. Making the relationship more believable was the fact that it operated at a temporal remove. Fifteen years after a decline in nine infectious diseases, we see the most noticeable uptick gender equality. Essentially, it takes almost a generation for the environmental conditions to affect social ones. The researchers got these results by looking at CDC data on the prevalence of tuberculosis, syphilis, gonorrhea, malaria, typhoid, diphtheria, pertussis, measles, and polio in the US. As a point of comparison, they looked at deaths from measles and tuberculosis in the UK. In both countries, the pattern was the same. As diseases dropped, gender equality rose.