Infectious diseases and gender equality are unrelated, right? Wrong, says research

With the recent election of Donald Trump as president-elect of the US it may not seem like it, but gender equality has steadily increased in the country over the last few decades. Common explanations for this include things like increasing feminism and civil rights for everyone. But now a new study, published in Nature Human Behaviour, suggests that the prevalence of infectious diseases may have played a big role in this – and might even hold a clue for how to boost gender equality further.

Researchers are increasingly examining ecological causes for explaining cultural features such as the prevalence of egalitarian attitudes in a region. The new study did exactly this when looking at changes in gender equality in the US and UK in recent decades.

In the US analysis, the researchers examined changes in gender inequality between 1951 to 2013. To estimate levels of gender equality, they looked at the number of women in the US Congress, male to female wage ratio, use of male versus female pronouns in published books and the percentage of respondents in Gallup polls preferring a male boss.

Using these they reported a strong decline in gender inequality over the last few decades. Of the ecological causes of gender equality that they examined, including resource scarcity, war and climatic stress, they found that infectious diseases were – by far – the most relevant.

Disease and conservatism

But can something like disease really cause gender inequality? Infectious diseases such as tuberculosis, measles and malaria could impact gender inequality in two different ways.

In regions where infectious diseases are prominent people tend to emphasise conservative, traditional ways of doing things. Here people are more authoritarian, religious and supportive of gender inequality.

These traditional values are considered adaptive responses to the problem of infectious diseases. This is because people must provide support to their sick family and friends, and be wary and avoidant of other group individuals to reduce the possibility of contracting new infections. This creates strong family ties, more suspicious views of others and heightened religiosity. According to this way of thinking, as infectious disease problems increase or decrease, so too should conservative values, such as the endorsement of gender inequality.

The second way in which infectious disease could cause inequality is related to females and their offspring. Imagine a girl growing up in a region with many people around her getting sick or dying. Her best option in this scenarios is to focus on making babies early and often. In such cases, her time is tied up in caring for her babies or the babies of her relatives. This leaves little time for her to live a life that is similar to a man’s, especially considering the types of jobs she might have or simply what she does with her life.

However, in places where infectious disease problems are much less worrisome and she has a greater chance of living longer, a woman has the time to put off having babies until much later in life. She then can have a life more similar to her male counterpart. In this view, we can expect gender inequality to decrease as infectious diseases become less of a threat over time.

But which came first, changes in infectious diseases or changes in gender inequality? The researchers looked at this and found that, largely, infectious diseases declined years before gender equality increased. The biggest correlation was a decline in infectious diseases 15 years before the corresponding decline in gender inequality. Overall, the highest inequality year was 1966 and the lowest was 2010.

The researchers also wanted to know if the effects of infectious diseases were affecting gender equality through changing conservative attitudes towards gender inequality versus women’s reproductive decisions. They found that infectious diseases acted primarily through reproductive decisions (measured as teen birth rates). That is, over time as the problem of infectious diseases decline, women are able to delay having babies and through this we see increasing gender equality.

Reliable results?

But how do we know that this correlation wasn’t just a coincidence? To strengthen their findings, the researchers replicated their study for the UK. Using similar measures, such as the number of women in parliament, for example, they reported the same pattern between infectious diseases and gender inequality and the role of early reproduction in the UK as the US. Here, though, they reported the largest correlation, and hence, lag, was about 25 years. The highest level of inequality was 1970 and lowest was 2014 according to their measure.

As they note, their analyses doesn’t definitively rule out other causes for increasing gender equality. But taking their findings at face value, if people want girls to have similar opportunities as boys, then reducing the problem of infectious diseases by increasing vaccination and sanitation looks to be a place to affect change.

A careful examination of the changes in gender inequality over the last few decades shows that despite the general declining trend there are occasional increases in gender inequality. It’s suggestive that the US just decided against a woman president in favour of a male conservative that we may be in the midst of one of those upticks in gender inequality. Maybe if we look back we might one day find an uptick in infectious diseases.