Monogamy in Early Humans Exists Due to Sexually Transmitted Infections, Study Shows

A new research suggests that early humans may have stop being polygamous and stick with one woman for the rest of their lives due to the spread of sexually transmitted infections (STI).

The study, published in the journal Nature Communications, reveals the impact of sexually transmitted infections, such as chlamydia, gonorrhea and syphilis, in early humans' shift from polygamy to monogamy.

For the study, researchers used a simulation model, like Sim City or a video game, to explore how the interactions between group size, sexually transmitted infections and social norms can explain the timing and emergence of socially imposed monogamy.

"It's a model about monogamist norms and not behaviour per se," said Chris Bauch, professor of applied mathematics and a university research chair at University of Waterloo and author of the study.

"We're really interested in explaining the social norms about monogamy. Why do people have these social institutions to support monogamy and why do they get enforced?" Bauch added.

Researchers found out that the sexually transmitted infections in small polygyny groups during the hunting-gathering age were short-lived due to their small numbers.

However, with the rise of the agriculture age, early humans learned to settle down and developed large communities. In large societies where polygamous is the norm, sexually transmitted infections became endemic impacting fertility.

According to CBC News, the impact of STI in fertility made early males realize that it is more advantageous to mate with only one partner, which instigated the rise of monogamous relationships.

Men under monogamous relationships punish polygamous males to improve their social foothold and protect them from STI. These resulted to the development of socially imposed monogamy, researchers said.

While the models used by the researchers are quite convincing, other scientists describe their theory as "unlikely."

Kit Opie of University College, London said in The Guardian, that polygamous relationship during the early hunter-gatherer age may be allowed but it is very rarely practiced by the early humans.