Germs, Not True Love, Make Humans Mate for Life

Why did humans become monogamous, apparently rejecting the promiscuity that is natural to most animals?

Was it morality? Religion? Maybe love?

The answer is germs, researchers said Tuesday, arguing that the havoc caused by sexually transmitted diseases (STIs) convinced our ancestors it would be better to mate for life.

A research duo from Canada and Germany observed that STIs flourished among large groups of people living in the villages, towns and cities that arose after prehistoric hunter-gatherers settled down to farm.

Left unchecked, spreading diseases can affect individual fertility and a group’s overall reproduction rate.

Falling population numbers would force a rethink of sexual behavior — which in turn gives rise to social mores.

The researchers developed a mathematical model of hunter-gatherer demographics and likely STI spread among them.

They used it “to show how growing STI disease burden in larger residential group sizes can foster the emergence of socially imposed monogamy in human mating.”

In small groups of no more than 30 individuals, with no chance for epidemic spread, STI outbreaks are generally short-lived, the team said.

http://news.discovery.com/human/evolution/germs-not-true-love-make-humans-mate-for-life-160412.htm