Welcome to brain stuff from how stuff works, Hey, brain stuff luring vogel bomb. Here, consider the humble prairie vole. Unlike of species, prairie voles are faithfully monogamous. Their lives may be short. They're an easy snack for hawks and snakes, but once two prairie voles mate, they are bonded until the end. Not so at the prairie voles close genetic cousin, the philandering montane vole. Montane voles form weak social bonds and prefer the mating strategy of use them and lose them.
The stark differences in mating behavior between these two voles species have made them excellent subjects for decoding the genetic roots of sexual monogamy and infidelity. According to a number of studies, prairie voles have more receptors in their brains for a hormone called vasopressin, which is believed to play
a key role in pair bonding. Not only do the faithful prairie voles have more of these receptors than they're cheating cousins, but the receptors are located in a part of the brain that's closer to the reward center, so When prairie voles mate, their bodies produce vasopressin, which causes their brains to reward the vole couple with a flood
of pleasurable emotions, sealing the social bond. The brains of montane voles, on the other hand, have far fewer vasopressin receptors and therefore make much weaker connections between pair bonding and pleasure. So it's on to the next conquest. The location and sensitivity of hormone receptors is dictated by our genes, which naturally leads to the question could the urge to cheat on our romantic partners be partly a product of
our genes? Are some of us walking around with prairie vole brains while others are stuck with the wandering eye of a montane vole. The real stories about the roots of infidelity and monogamy are far more complicated than whether you have a cheating gene. Human sexual behavior is the product of countless influences and interactions, from our early relationships with our parents, to social norms around sexuality, to yes
our genetic predispositions. We spoke with Justin Garcia, and volutionary biologist and sex researcher at the pioneering at Kinsey Institute at Indiana University. He said, we are never prisoners of our biology, but it does explain why some people wake up with somewhat different motivations in these areas than other people. The influence of these different genetically based motivations is difficult to quantify, but study by Australian researcher Brendan z Each
offers some intriguing clues. Z Each surveyed these sexual habits of nearly seven thousand, four hundred twins and siblings in Finland and found that nine point eight percent of men and six point four percent of women had had more than one sexual partner in the past year. But the fascinating finding was that these sets of identical twins with identical genomes reported the exact same levels of fidelity, while
fraternal twins and regular siblings did not. That indicates that the variations and genes are powerful enough to influence sexual behavior beyond other environmental factors. In fact, z Each put a number on it. Our genes account for roughly sixty infidelity in males and four percent in females. Vasopresident isn't the only hormone that's been linked to varying levels of
monogamy and infidelity. Oxytocin is another hormone released during sex and also during childbirth and nursing that strengthens social bonds, and female voles with more oxytocin receptors are also more likely to mate for life. Garcia at the Kinsey Institute conducted a landmark study of dopamine receptors and sexual straying.
It's long been established that people with fewer or weaker dopamine receptors engage in riskier behavior a drug and alcohol abuse, and gambling to get the same dopamine rush that the average person might get from eating a Snickers. Garcia tested a hundred and eighty one participants, some of whom carried
the weaker DE four variant of the dopamine receptor. He found the people with the DE four receptor were fifty more likely to report sexual infidelity, and when he looked at all participants who cheated in the study, those with the defour receptor were far more likely to do it multiple times. For Garcia, the genetic evidence points to a more nuanced understanding of what it means when somebody cheats.
In a relationship. He said, the classic explanation is that they're not really in love, but maybe they're more motivated by other feelings of sensation, risk, and novelty. Today's episode was written by Dave Ruse and produced by Tyler Clang. For more on this and lots of other sensational topics, visit our home planet, how Stuff Works dot com.