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Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey

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Speaker 1: brain Stuff, Lauren Vogelbaum here with a classic episode from

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Speaker 1: our archives. There are lots of ways for humans to

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Speaker 1: conduct romantic or sexual relationships, be they monogamous or non monogamous,

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Speaker 1: and we are not the only animals that vary these practices.

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Speaker 1: Today's question is could part of this behavior be genetic?

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Speaker 1: Hey brain Stuff, Lauren Vogelbaum. Here, consider the humble prairie vowle.

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Speaker 1: Unlike of species, prairie voles are faithfully monogamous. Their lives

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Speaker 1: may be short, they're an easy snack for hawks and snakes,

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Speaker 1: but once two prairie voles mate, they are bonded until

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Speaker 1: the end. Not so with the prairie voles close genetic cousin,

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Speaker 1: the philandering montane vole. Montane voles form weak social bonds

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Speaker 1: and prefer the mating strategy of use them and lose them.

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Speaker 1: The stark differences in mating behavior between these two voles

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Speaker 1: species have made excellent subjects for decoding the genetic roots

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Speaker 1: of sexual monogamy and infidelity. According to a number of studies,

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Speaker 1: prairie voles have more receptors in their brains for a

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Speaker 1: hormone called vasopressin, which is believed to play a key

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Speaker 1: role in pair bonding. Not only do the faithful prairie

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Speaker 1: voles have more of these receptors than their cheating cousins,

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Speaker 1: but the receptors are located in a part of the

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Speaker 1: brain that's closer to their reward center. So when prairie

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Speaker 1: voles mate, their bodies produced vasopressin, which causes their brains

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Speaker 1: to reward the vole couple with a flood of pleasurable emotions,

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Speaker 1: sealing the social bond. The brains of montane voles, on

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Speaker 1: the other hand, have far fewer vasopressin receptors and therefore

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Speaker 1: make much weaker connections between pair bonding and pleasure. So

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Speaker 1: it's on to the next conquest. The location and sensitivity

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Speaker 1: of hormone receptors is dictated by our genes, which naturally

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Speaker 1: leads to the question could the urge to cheat on

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Speaker 1: our romantic partners be partly a product of our genes?

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Speaker 1: Are some of us walking around with prairie vole brains

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Speaker 1: while others are stuck with the wandering eye of a

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Speaker 1: montane vole. The real stories about the roots of infidelity

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Speaker 1: and monogamy are far more complicated than whether you have

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Speaker 1: a cheating gene. Human sexual behavior is the product of

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Speaker 1: countless influences and interactions, from our early relationships with our parents,

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Speaker 1: to social norms around sexuality, to yes our genetic predispositions.

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Speaker 1: We spoke with Justin Garcia, and evolutionary biologist and sex

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Speaker 1: researcher at the pioneering Kinsey Institute at Indiana University. He said,

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Speaker 1: we are never prisoners of our biology, but it does

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Speaker 1: explain why some people wake up with somewhat different motivations

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Speaker 1: in these areas than other people. The influence of these

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Speaker 1: different genetically based motivations is difficult to quantify, but study

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Speaker 1: by Australian researcher Brendan ze Each offers some intriguing clues.

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Speaker 1: Z Each surveyed these sexual habits of nearly seven thousand,

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Speaker 1: four hundred twins and siblings in Finland and found that

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Speaker 1: nine point eight percent of men and six point four

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Speaker 1: percent of women had had more than one sexual partner

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Speaker 1: in the past year. But the fascinating finding was that

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Speaker 1: these sets of identical twins with identical genomes reported the

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Speaker 1: exact same levels of fidelity, while fraternal twins and regular

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Speaker 1: siblings did not. That indicates that the variations and genes

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Speaker 1: are powerful enough to influence sexual behavior beyond other environmental factors.

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Speaker 1: In fact, each put a number on it. Our genes

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Speaker 1: account for roughly sixty three percent of infidelity in males

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Speaker 1: and four percent in females. Vasopresident isn't the only hormone

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Speaker 1: that's been linked to varying levels of monogamy and infidelity.

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Speaker 1: Oxytocin is another hormone released during sex and also during

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Speaker 1: childbirth and nursing that strengthens social bonds and female roles

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Speaker 1: with more oxytocin receptors are also more likely to mate

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Speaker 1: for life. Garcia at the Kinsey Institute conducted a landmark

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Speaker 1: study of dopamine receptors and sexual straying. It's long been

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Speaker 1: established that people with fewer or weaker dopamine receptors engage

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Speaker 1: in riskier behavior, drug and alcohol abuse, and gambling to

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Speaker 1: get the same dopamine rush that the average person might

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Speaker 1: get from eating a snickers. Garcia tested a hundred and

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Speaker 1: eighty one participants, some of whom carried the weaker D

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Speaker 1: four variant of the dopamine receptor. He found the people

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Speaker 1: with the D four receptor were more likely to report

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Speaker 1: sexual infidelity, and when he looked at all participants who

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Speaker 1: cheated in the study, those with the D four receptor

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Speaker 1: were far more likely to do it multiple times. For Garcia,

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Speaker 1: the genetic evidence points to a more nuanced understanding of

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Speaker 1: what it means when somebody cheats in a relationship. He said.

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Speaker 1: The classic explanation is that they're not really in love,

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Speaker 1: but maybe they're more motivated by other feelings of sensation, risk,

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Speaker 1: and novelty. Today's episode is based on the article good

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Speaker 1: Excuse or is there actually a cheating gene on how

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Speaker 1: stuff works dot com written by Dave Rouse. Brain Stuff

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Speaker 1: is production of I Heart Radio in partnership with how

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Speaker 1: stuff works dot Com, and it is produced by Tyler Clay.

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