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Why Men Cheat: A Surprising Lesson in Love And Brain Chemistry From the Animal Kingdom

Take a lesson from our furry friends: Cheating may be more chemical than emotional.

While humans and animals have differences in their mating strategies, scientists have observed some curious similarities. One of the most colorful examples of animal tactics is provided by the side-blotched lizard (Uta stansburiana).  Conveniently, the males come with three different colored throats that match their mating-styles. Males with orange throats use the alpha-male harem strategy. They guard a group of females and mate with all of them. The males with yellow throats are called “sneakers” because they cheat; they slip into the harem of the orange throat and mate with his females whenever they can get away with it. The males with brilliant blue throats – my personal favorites — use the one-and-only-strategy. They mate with one female and guard her 24-7. From a biological perspective, the approaches of the orange-throated harem leader, the yellow-throated sneaker and the blue-throated one-female type are all successful mating strategies for lizards and for human males too. I affectionately call my husband a “blue-throat.”

The Monogamy Hormone:

So, women may be anxiously asking, “How can I pick a blue-throat?”  We have no sure-fire answer yet on what makes for a monogamous human male mate, but the research on furry little mammals called voles might provide some clues. Scientists have found that male prairie voles are monogamous and share equally in parenting their offspring. But their cousin — the montane vole— is strictly promiscuous, seeks sexual variety, and specializes in one-night stands that last less than a minute. The difference between the mating strategies of these vole cousins originates in the brain. When the prairie vole finds his partner, he mates with her over and over in a 24-hour sexual marathon. This sexual activity changes his brain forever. An area of his brain called the AH — the anterior hypothalamus– memorizes his partner’s smell and touch, leading him to aggressively reject all other females.   This blissful day in the new vole couple’s relationship is not only unforgettable, but biologically necessary. Memorizing her and thus merging the so-called love and lust circuits in his brain will initiate a lifelong preference for this one female.

During sex, both prairie and montane voles release vasopressin and dopamine, but only the prairie vole has the type of vasopressin receptors in his brain needed to make him monogamous.  And when scientists experimentally blocked these monogamy-inducing vasopressin receptors in the prairie voles’ brains, they didn’t bond with their sexual partners.  The love and lust circuits in their brains couldn’t merge.  What makes the difference between the vasopressin receptors in the prairie vole brain and the montane vole brain is their differing genes. The monogamous vole’s vasopressin receptor gene is a longer version and the promiscuous vole’s is a shorter version. When scientists inserted the long version of the gene into the promiscuous montane vole, he too became monogamous.

Although the brain biology in men may turn out to be more complicated than it is in voles, humans have this vasopressin receptor gene too.  Some men have the long version while others have the short one. A study in Sweden found that men with the long version of the vasopressin receptor gene were twice as likely to leave bachelorhood behind and commit to one woman for life.   A ‘good man’ just became easier to find.



Photo Credit: Shutterstock

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