“We are accustomed to thinking of sexual infidelity as a symptom of an unhappy relationship, a moral flaw or a sign of deteriorating social values. When I was trained as a psychiatrist we were told to look for various emotional and developmental factors — like a history of unstable relationships or a philandering parent — to explain infidelity.
“But during my career, many of the questions we asked patients were found to be insufficient because for so much behavior, it turns out that genes, gene expression and hormones matter a lot.
“Now that even appears to be the case for infidelity.
“We have long known that men have a genetic, evolutionary impulse to cheat, because that increases the odds of having more of their offspring in the world.
“But now there is intriguing new research showing that some women, too, are biologically inclined to wander, although not for clear evolutionary benefits. Women who carry certain variants of the vasopressin receptor gene are much more likely to engage in “extra pair bonding,” the scientific euphemism for sexual infidelity.”
(Richard Friedman, The New York Times, “Infidelity Lurks in Your Genes,” 22 May 2015)