Biology Prevents Men to Pursue Friends' Wives

Males become less sexually inclined when interacting with the marital partner of a close friend, according to a study of associated testosterone levels in men.

"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."

The reason for the evolutionary development of this biological filter in partner selection can be found in the beneficial outcome for social cooperation, said Flinn. 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.

Flinn also sees a present day and global perspective in the uncovered mechanism, that sheds light at the evolutionary development of human societies, leading to todays global civilization.

"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 present findings, published under the title "Hormonal Mechanisms for Regulation of Aggression in Human Coalitions" in the journal Human Nature, might also be associated with another study about human sexual selection that showed that men who cheat on their wives tend to have a lower IQ.

The 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, which indicates that those men had more (surviving) offspring.

"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.