WEBVTT -  Is There a Gene for Infidelity?

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<v Speaker 1>Welcome to brain stuff from how stuff works, Hey, brain

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<v Speaker 1>stuff luring vogel bomb. Here, consider the humble prairie vole.

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<v Speaker 1>Unlike of species, prairie voles are faithfully monogamous. Their lives

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<v Speaker 1>may be short. They're an easy snack for hawks and snakes,

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<v Speaker 1>but once two prairie voles mate, they are bonded until

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<v Speaker 1>the end. Not so at the prairie voles close genetic cousin,

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<v Speaker 1>the philandering montane vole. Montane voles form weak social bonds

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<v Speaker 1>and prefer the mating strategy of use them and lose them.

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<v Speaker 1>The stark differences in mating behavior between these two voles

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<v Speaker 1>species have made them excellent subjects for decoding the genetic

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<v Speaker 1>roots of sexual monogamy and infidelity. According to a number

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<v Speaker 1>of studies, prairie voles have more receptors in their brains

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<v Speaker 1>for a hormone called vasopressin, which is believed to play

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<v Speaker 1>a key role in pair bonding. Not only do the

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<v Speaker 1>faithful prairie voles have more of these receptors than they're

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<v Speaker 1>cheating cousins, but the receptors are located in a part

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<v Speaker 1>of the brain that's closer to the reward center, so

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<v Speaker 1>When prairie voles mate, their bodies produce vasopressin, which causes

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<v Speaker 1>their brains to reward the vole couple with a flood

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<v Speaker 1>of pleasurable emotions, sealing the social bond. The brains of

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<v Speaker 1>montane voles, on the other hand, have far fewer vasopressin

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<v Speaker 1>receptors and therefore make much weaker connections between pair bonding

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<v Speaker 1>and pleasure. So it's on to the next conquest. The

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<v Speaker 1>location and sensitivity of hormone receptors is dictated by our genes,

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<v Speaker 1>which naturally leads to the question could the urge to

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<v Speaker 1>cheat on our romantic partners be partly a product of

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<v Speaker 1>our genes? Are some of us walking around with prairie

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<v Speaker 1>vole brains while others are stuck with the wandering eye

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<v Speaker 1>of a montane vole. The real stories about the roots

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<v Speaker 1>of infidelity and monogamy are far more complicated than whether

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<v Speaker 1>you have a cheating gene. Human sexual behavior is the

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<v Speaker 1>product of countless influences and interactions, from our early relationships

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<v Speaker 1>with our parents, to social norms around sexuality, to yes

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<v Speaker 1>our genetic predispositions. We spoke with Justin Garcia, and volutionary

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<v Speaker 1>biologist and sex researcher at the pioneering at Kinsey Institute

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<v Speaker 1>at Indiana University. He said, we are never prisoners of

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<v Speaker 1>our biology, but it does explain why some people wake

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<v Speaker 1>up with somewhat different motivations in these areas than other people.

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<v Speaker 1>The influence of these different genetically based motivations is difficult

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<v Speaker 1>to quantify, but study by Australian researcher Brendan z Each

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<v Speaker 1>offers some intriguing clues. Z Each surveyed these sexual habits

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<v Speaker 1>of nearly seven thousand, four hundred twins and siblings in

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<v Speaker 1>Finland and found that nine point eight percent of men

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<v Speaker 1>and six point four percent of women had had more

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<v Speaker 1>than one sexual partner in the past year. But the

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<v Speaker 1>fascinating finding was that these sets of identical twins with

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<v Speaker 1>identical genomes reported the exact same levels of fidelity, while

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<v Speaker 1>fraternal twins and regular siblings did not. That indicates that

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<v Speaker 1>the variations and genes are powerful enough to influence sexual

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<v Speaker 1>behavior beyond other environmental factors. In fact, z Each put

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<v Speaker 1>a number on it. Our genes account for roughly sixty

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<v Speaker 1>infidelity in males and four percent in females. Vasopresident isn't

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<v Speaker 1>the only hormone that's been linked to varying levels of

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<v Speaker 1>monogamy and infidelity. Oxytocin is another hormone released during sex

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<v Speaker 1>and also during childbirth and nursing that strengthens social bonds,

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<v Speaker 1>and female voles with more oxytocin receptors are also more

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<v Speaker 1>likely to mate for life. Garcia at the Kinsey Institute

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<v Speaker 1>conducted a landmark study of dopamine receptors and sexual straying.

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<v Speaker 1>It's long been established that people with fewer or weaker

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<v Speaker 1>dopamine receptors engage in riskier behavior a drug and alcohol abuse,

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<v Speaker 1>and gambling to get the same dopamine rush that the

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<v Speaker 1>average person might get from eating a Snickers. Garcia tested

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<v Speaker 1>a hundred and eighty one participants, some of whom carried

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<v Speaker 1>the weaker DE four variant of the dopamine receptor. He

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<v Speaker 1>found the people with the DE four receptor were fifty

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<v Speaker 1>more likely to report sexual infidelity, and when he looked

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<v Speaker 1>at all participants who cheated in the study, those with

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<v Speaker 1>the defour receptor were far more likely to do it

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<v Speaker 1>multiple times. For Garcia, the genetic evidence points to a

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<v Speaker 1>more nuanced understanding of what it means when somebody cheats.

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<v Speaker 1>In a relationship. He said, the classic explanation is that

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<v Speaker 1>they're not really in love, but maybe they're more motivated

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<v Speaker 1>by other feelings of sensation, risk, and novelty. Today's episode

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<v Speaker 1>was written by Dave Ruse and produced by Tyler Clang.

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<v Speaker 1>For more on this and lots of other sensational topics,

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<v Speaker 1>visit our home planet, how Stuff Works dot com.