Two different genes in your DNA may play a role in whether or not you stay faithful: a section of the vasopressin receptor known as RS3 334 and the DRD4 gene. Does that mean, theoretically, you could get your partner genetically tested to find out if (s)he will stay faithful? One study started when scientists noticed prairie voles remain in life-long monogamous relationships while their close kin the meadow voles enjoy staying single and living promiscuous lives. Why? Well, when the male prairie vole repeatedly mates with the same female prairie vole, the hormone vasopressin gets released in his brain. This hormone then binds to receptors and creates a pleasurable feeling that becomes associated with that particular female, creating “pair-bonding” (aka monogamy). If you block this hormone the monogamy disappears, or you can transform a polygamous male to a monogamous one by using genetic techniques to boost the levels of vasopressin.
But obviously we aren’t prairie or meadow voles, so does the human brain work the same way? According to researchers at the Karolinska Institute in Sweden, the section of the gene called RS3 334 comes in variable numbers in human beings. Men can have no copies, one copy, or two copies. The more copies a man has, the more likely he is to cheat since each copy weakens the effect of the vasopressin hormone. So men with two copies are more likely to remain single, and if they do get married they’re more likely to have marital troubles.
Any of you familiar with oxytocin (sometimes called the “cuddle chemical” or “love hormone”) may be thinking that vasopressin sounds awfully familiar. You’re not wrong, however there is a lot of misinformation about oxytocin out there. One of the most pervasive myths is that when a woman has an orgasm oxytocin gets released into her system, making her feel emotionally bonded to the male who gave her the orgasm. This myth is then typically used to say women are unable to have casual sex the way a man can because of this chemically-induced emotional bond.
Yes, oxytocin does create bonds. Women have high levels of it during pregnancy, fathers get an oxytocin boost when playing with their babies, and people falling in love typically have oxytocin levels spike. But there are no definitive studies showing the role oxytocin has in sex and emotional involvement. It is true that women whose brains have more oxytocin tend to have more sex than women with less oxytocin, but considering a person can get an oxytocin boost from hugs, back massages, or even chick flicks there would be an awful lot of unintentional emotional bonding creating all sorts of trouble if oxytocin had that big a role.
Aside from vasopressin receptors, there’s another gene that’s recently been found to play a role in infidelity too. Justin Garcia (investigator and SUNY Doctoral Diversity Fellow at the State University of New York in Birmingham) led a study of both men and women and found a genetic variation that can influence sexual behavior. It’s on the DRD4 gene – formerly known as the “thrill-seeking gene” for its role in releasing dopamine, but now being called the “love rat gene”. When people with a variation of the DRD4 gene known as 7R+ have an affair, they get a dopamine rush similar to what a gambler gets when he wins big or an alcoholic has when enjoying a drink. The release of dopamine in the body triggers feelings of pleasure and reward. Garcia explained, “What we found was that individuals with a certain variant of the DRD4 gene were more likely to have a history of uncommitted sex, including one-night stands and acts of infidelity.”
Thus, people who have the 7R+ variation of DRD4 are more likely to commit infidelity or be promiscuous. In Garcia’s study, 50% of people with 7R+ admitted to cheating versus 22% of people without the genetic variation. And the infidelity typically included more one-night stands. This applied equally to both men and women. But Garcia did add that his results suggest a person can feel committed to his/her partner and still feel the desire to be unfaithful.
Yet keep in mind both with the 7R+ variation and vasopressin receptors we aren’t slaves to our genes. Not everyone with these genetic variations will exhibit unfaithful or promiscuous behavior. Environment and choice play important roles. These studies simply show that people who have certain genetic variations are more likely to cheat, not that they all will.