Is There a Gene for Infidelity?

Some animals mate for life -- and others decidedly don't. Learn what researchers have discovered about cheating by studying voles and humans alike in this episode of BrainStuff.

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:02):
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

(00:22):
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

(00:43):
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

(01:05):
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,

(01:26):
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

(01:47):
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

(02:10):
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

(02:32):
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

(02:56):
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

(03:18):
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

(03:40):
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

(04:02):
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.

(04:23):
For more on this and lots of other sensational topics,
visit our home planet, how Stuff Works dot com.