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How The Brain Falls in Love


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In his lab at Yerkes, Young studies rodents called prairie voles. Unlike 95 percent of mammals, prairie voles mate for life.

“They form a lifelong bond,” Young said. “They nest together, they raise a family together, they have another litter. So they have this really intense bond between them.”

In a series of studies, Young found that the hormones that produce that bond are the same ones that promote parent-child bonding in many other species.

For females, that hormone is oxytocin.

“We can take a prairie vole female, inject her with oxytocin, and she’ll bond with whatever male is around,” Young said.

For males, a related hormone called vasopressin promotes both pair bonding and fatherly behaviors like grooming young voles.

But like humans, some voles are more suited for monogamy than others. In one recent study, Young found that male voles with a particular variant of a gene called AVPR1A that codes for vasopressin receptors in the brain had fewer of those receptors than usual. And so, perhaps not surprisingly, voles with that gene variant were less likely to bond with females than voles without it.

In another study, Young found that implanting a version of the AVPR1A gene in meadow voles — a related species that does not mate for life — produced never-before-seen monogamous meadow voles.

Recently, Swedish researcher Hasse Walum of the Karolinska Institute in Stockholm found that a related gene in human males has similar effects.

In a study published in September in the Proceedings of the National Academies of Science, Walum studied a version of the AVPR1A gene that codes for vasopressin receptors in men. He studied more than 1,000 Swedish men, and found that men who carried a particular variant of the gene were less likely to be married than men without the variant, were more likely to report a recent crisis in their marriage, and ranked lower on a scale of partner bonding that asked questions such as “how often do you kiss your mate?”

So if I understand correctly, the reason some humans are more prone to monogamy -- and others are less prone -- has to do with hormone quantities?

Yes, hormone quantities, specifically oxytocin and vasopressin.  How much you have activated, depends on how many receptors you have, for the the one specific to your gender.  How many receptors depends on your genetics.   I guess some of us are just not wired for monogamy, maybe those labeled as commitment-phobes just lack the receptors, so they just don't feel any connection/bonding.

That's a profound thought that calls into question free will, given genetic predispositions.

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