In movies, books, and sometimes even real life, you often hear stories of men sleeping with their best friends’ wives. But in reality, that happens a lot less that you’d think. In fact, men may actually be biologically to stay away from the fruit of the forbidden tree (isn’t that poetic?).
Researchers at the University of Missouri have found that although men’s testosterone levels rise when they’re interacting with someone they want to have sex with—or the wife of an enemy—testosterone takes a dive when they’re hanging out with the wife of a close friend. “Although men have many chances to pursue a friend’s mate, propositions for adultery are relatively rare on a per opportunity basis,” says anthropologist Mark Flinn, Ph.D. “[M]en’s minds have evolved to foster a situation where the stable pair bonds of friends are respected.”
Flinn suggests that this biological anti-aphrodisiac seems to have evolved over a very long time. He believes that men who were constantly betraying their friends’ trust and endangering the stability of families may have caused a survival disadvantage for their entire communities. “A community of men who didn’t trust each other would be brittle and vulnerable to attack and conquest. The costs of an untrustworthy reputation would have outweighed the benefits of having extra offspring with a friend’s conjugal companion.”
The same drop in testosterone has been seen in new fathers right after the birth of their baby—biological encouragement for dads to care for their babies.
The study was just published in journal Human Nature.