Men May Have Natural Aversion To Sleeping With Friends' Wives

Coveting thy neighbor's wife might become a thing of the past, according to a new study of testosterone levels in men that indicates males become less sexually inclined when interacting with the marital partner 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," said Mark Flinn, professor of anthropology at the University of Missouri, in a statement.

"Men's testosterone levels generally increase when they are interacting with a potential sexual partner or an enemy's mate. However, our findings suggest that men's minds have evolved to foster a situation where the stable pair bonds of friends are respected."

Flinn said that evolutionarily, men who constantly betrayed friends' trust and endangered family stability put their whole community at a disadvantage for survival, because a community of men who did not trust each other would be brittle and vulnerable to attack.

The findings, Flinn said, might help solve global problems.

"Ultimately, our findings about testosterone levels illuminate how people have evolved to form alliances," he said. "Using that biological understanding of human nature, we can look for ways to solve global problems. The same physiological mechanisms that allow villages of families to coexist and cooperate can also allow groups like NATO and the U.N. to coordinate efforts to solve common problems. The more we view the Earth as a single community of people, the greater our ability to solve mutual threats, such as climate change."

The findings might also be associated with natural selection, as men who cheat on their wives have also been found to have a lower IQ.

A 2010 study by evolutionary psychologist Satoshi Kanazawa at the London School of Economics and Political Science concluded that the smarter a man is the less likely he is to cheat on his partner.

"The theory predicts more intelligent men are more likely to value sexual exclusivity than less intelligent men," said Kanazawa, as reported by the Daily Mail. 

The study "Hormonal Mechanisms for Regulation of Aggression in Human Coalitions" was published in the journal Human Nature.