STIs, peer pressure drove ancient humans to monogamy

Washington DC: According to a recent study, the root of marriage can be traced back to nothing romantic, rather it may have been started just to avoid sexually transmitted diseases (STIs).

The University of Waterloo study found that prehistoric humans may have developed social norms that favour monogamy and punish polygamy thanks to the presence of STIs and peer pressure.

As hunter-gatherers began living in larger populations of early settled agriculturalists, the spread of STIs could explain a shift towards the emergence of social norms that favoured one sexual partner over many.

The work uses computer modeling techniques to simulate the evolution of different social mating behaviours in human populations based on demographic and disease transmission parameters.

Researcher Chris Bauch said that 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. The study illustrates how mathematical models are not only used to predict the future, but also to understand the past.

The study, by Professor Bauch and Richard McElreath from the Max Planck Institute for Evolutionary Anthropology, found that when population sizes become large, the presence of STIs decreases fertility rates more among males with multiple partners, therefore changing which mating behaviour proves to be most beneficial to individuals and groups.

"Our social norms did not develop in complete isolation from what was happening in our natural environment. On the contrary, we can't understand social norms without understanding their origins in our natural environment," Professor Bauch. "Our social norms were shaped by our natural environment. In turn, the environment is shaped by our social norms, as we are increasingly recognizing."

The researchers note that STIs may be one factor among many, including female choice, pathogen stress and technological impacts that altered human behavior from polygamy to monogamy.

The study appears in journal Nature Communications.