According to the General Social Survey at the University of Chicago’s independent research organization, NORC, over the past two decades, the rate of infidelity has been pretty constant at around 21 percent for married men, and between 10 to 15 percent for married women, 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 but it turns out that genes, gene expression and hormones matter a lot In the case of 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.
In a study of nearly 7,400 Finnish twins and their siblings who had all been in a relationship for at least one year found that 9.8 percent of men and 6.4 percent of women reported that they had two or more sexual partners in the previous year. His study, published last year in Evolution and Human Behavior, found a significant association between five different variants of the vasopressin gene and infidelity in women only and no relationship between the oxytocin genes and sexual behavior for either sex.
That was impressive: Forty percent of the variation in promiscuous behavior in women could be attributed to genes. Other studies confirm that oxytocin and vasopressin are linked to partner bonding, which bears on the question of promiscuity since emotional bonding is, in a sense, the inverse of promiscuity.
Now, before you run out and get your prospective partner genotyped for his or her vasopressin and oxytocin receptor genes, two caveats: Correlation is not the same as causation; there are undoubtedly many unmeasured factors that contribute to infidelity. And rarely does a simple genetic variant determine behavior.
Still, there is a good reason to take these findings seriously: Data in animals confirm that these two hormones are significant players when it comes to sexual behavior.
Experiments in which oxytocin and vasopressin are directly administered to humans show these hormones have effects that go beyond sex; they appear to increase trust and social bonding.
Sexual monogamy is distinctly unusual in nature: Humans are among the 3 to 5 percent of mammalian species that practice monogamy, along with the swift fox and beaver — but even in these species, infidelity has been commonly observed.
The evolutionary benefit of promiscuity for men is pretty straightforward: The more sexual partners you have, the greater your potential reproductive success. But women’s reproductive capacity is more limited by biology. So what’s in it for women? There may be no clear evolutionary advantage to female infidelity, but sex has never just been about procreation. Cheating can be intensely pleasurable because, among other things, it involves novelty and a degree of sensation seeking, behaviors that activate the brain’s reward circuit.
For some, there is little innate temptation to cheat; for others, sexual monogamy is an uphill battle against their own biology.
Source http://mobile.nytimes.com/2015/05/24/opinion/sunday/infidelity-lurks-in-your-genes.html?referrer&_r=0