Monogamy May Have Been a Prehistoric Response to STDs

Are social norms the cause of monogamy or did sexually transmitted diseases (STDs) drive primitive cultures to the practice in order to survive? A new study says it’s the latter. Would the eradication of STDs bring back widespread polygamy?

Researchers at the University of Waterloo in Canada decided to find out. To the disappointment of college students lined up to be test sex subjects or get free penicillin, their study was conducted using mathematical models to simulate prehistoric communities with varying levels of polygamy, ratios of hunter-gathers to agriculturalists and levels of diseases.

According to Nature Communications, where the results were published, the study found that early hunter-gatherers lived in smaller groups with a few males and many females for the creation of many more children. The models showed that outbreaks of STDs in small groups burned out (pun intended) quickly and did not affect the growth of the group’s population.

The situation changed when they modeled the move from hunter-gatherer to early farming. The populations of those societies became larger, allowing sexually transmitted diseases to spread quicker and to more individuals, causing a decrease in the fertility rate. It would be advantageous for one healthy male to have (and protect) just one healthy female that he kept from other males for his own mating purpose, and the model reflected this. As the number of monogamous pairs increased, fertility also increased while the number of predicted STD incidents and the size and speed of the outbreaks both decreased.

Chris Bauch, professor of applied mathematics at the University of Waterloo and the study’s co-author, describes the implications of their findings.

This research shows how events in natural systems, such as the spread of contagious diseases, can strongly influence the development of social norms and in particular our group-oriented judgments.

In other words, the natural need preceded the social norm. In addition, the health and fertility benefits of monogamy drove the societies to punish those polygamists who did not practice them.

While modern medicine has reduced the spread of STDs (although obviously not eradicated them), the social norms against polygamy continue, as Bauch points out.

Our social norms were shaped by our natural environment. In turn, the environment is shaped by our social norms, as we are increasingly recognizing.

Should we allow or accept polygamy again, provided it’s voluntary and not forced or coerced? Good luck with that. Should we look at other social norms and determine if they’ve outlived their original purpose? Definitely.

Any suggestions on which one should be the first?