Science Sunday: Do Our Genes Make Us Do It?

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Mistress and Slave continue our efforts to find a little privacy as we cope with our newly crowded house.  Sex in the morning, before we hear our little “Divas in training” up and about is one way.  Then yesterday, before Mistress headed to our swim club, and I went to stop by to check out my grandkids, we discovered that our kids had suddenly disappeared.  I was able to coax Mistress into a few moments of worship before she went on her “sun worship” mission.

“Do you mind just sliding my bathing suit aside, Slave…..”

“Of course not, Mistress….”

For once she did not have to suppress those little sounds of delight as I went about my business.

But today’s entry has a higher purpose than simply the play-by-play from here in our re-infested nest. I am reporting on an intriguing summary of recent scientific research that suggests there may be a genetic explanation for a woman’s impulse to cuckold her mate.  In this morning’s NY Times there is an opinion piece (Infidelity Lurks in Our Genes) by science writer Richard Friedman about how genes may pre-determine what he describes as “infidelity”, but presumably also incorporates the contractual right to enjoy the company of an occasional “side dish” that Mistress enjoys.

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.

Brendan P. Zietsch, a psychologist at the University of Queensland, Australia, has tried to determine whether some people are just more inclined toward 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, Dr. Zietsch looked at the link between promiscuity and specific variants of vasopressin and oxytocin receptor genes. Vasopressin is a hormone that has powerful effects on social behaviors like trust, empathy and sexual bonding in humans and other animals. So it makes sense that mutations in the vasopressin receptor gene — which can alter its function — could affect human sexual behavior.

He 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. That is surprising since, as Dr. Zietsch points out, there are so many other factors that are necessary for promiscuous encounters, like circumstance and the availability of a willing and able partner. Although this is the largest and best study on this, it’s not clear why there was no relationship between the vasopressin gene and promiscuous behavior in men.

The article goes onto describe tests conducted on two variations of the vole “family” that may confirm this genetic impulse to stray from the marital bed. It turns out that Montane Voles are prone to have a wandering eye, while Prairie Voles are relatively monogamous. Until the evil scientist begins his experiment:

In the monogamous prairie voles, the vasopressin receptors are close to the brain’s reward center, but in the philandering montane voles, these same receptors are mostly found in the amygdala, a brain region that is critical to processing anxiety and fear.

So mating for the prairie voles activates the pleasurable reward pathway, which reinforces mating and promotes attachment and thus monogamy. For the promiscuous montane voles, sex has little effect on attachment; any vole will do.

It is even possible experimentally to take a home-wrecking montane vole and make him behave like a family-oriented prairie vole. Using a virus as a delivery vehicle to transmit the vasopressin receptor gene, it’s easy to artificially boost the number of vasopressin receptors in the brain’s reward center, and make a male vole behave monogamously. The story for female voles is similar except that it is oxytocin, not vasopressin, that triggers monogamous behavior.

Of course, all of this potential for genetic manipulation has Slave’s imagination running wild:

1)  Could you make a potential spouse undergo a genetic test to calculate the likelihood that they would or would not take up with other lovers during the course of a marriage?

2)   If you feared a spouse was “cheating” could you order up a cocktail of “vasopressin” or “oxytocin” to get them back in line?

3)   And, even more deviously, suppose your wife had her eye on some guy who was married and annoyingly anonymous.  Could you spike his drink with a batch of genetic material that would make him more likely to loose his inhibitions?

All of this also made Slave wonder if there is a genetic explanation for what makes Slave enjoy it when his hot Mistress falls into the arms of another guy.  Do you think male Montane Voles get off when their female mate reports back on her encounter with another male Montane Vole? I guess I should have taken more science classes in college.