You Dirty Vole

Why are some voles fickle, others faithful? Vole brains differ from one creature to the next. Larry Young, a neuroscientist at Emory University, has found that some animals have more receptors for oxytocin and vasopressin than others. In a recent experiment, he injected a gene into male prairie voles that permanently upped the number of vasopressin receptors in their brains. The animals paired with females even though the two hadn't mated. "Normally they have to mate for at least 24 hours to establish a bond," he says. So the number of receptors can mean the difference between sticking around and skipping out after sex. Might these differences in brain wiring influence human faithfulness? "It's too soon to tell," Young says. But it's "definitely got us very curious."


How does evolution account for the often-conflicting experiences of love and lust, which have caused no small amount of destruction in human history? Fisher speculates that the neural systems of romantic love and attachment evolved for different reasons. Romantic love, she says, evolved to allow people to distinguish between potential mating partners and "to pursue these partners until insemination has occurred." Attachment, she says, "evolved to make you tolerate this individual long enough to raise a child." Pepper Schwartz agrees: "We're biologically wired to be socially monogamous, but it's not a good evolutionary tactic to be sexually monogamous. There need to be ways to keep reproduction going if your mate dies."


Many of our marriage customs, say sociologists, derive from the need to reconcile this tension. "As much as people love passion and romantic love," Schwartz adds, "most people also want to have the bonding sense of loyalty and friendship love as well." Marriage vows are a declaration about romantic love and binding attachment, but also about the role of rational thought and the primacy of mind and mores over impulses.


Scientists hope to do more than simply decode the biochemistry of the emotions associated with love and attachment. Some, like Insel, are searching for treatments for attachment disorders such as autism, as well as pathological behaviors like stalking and violent jealousy. It is not inconceivable that someday there might be sold an attachment drug, a monogamy pill; the mind reels at the marketing possibilities.


Lowell Getz, the grandfather of all this research, couldn't be more thrilled. "I spent almost $1 million of taxpayer money trying to figure out stuff like why sisters don't make it with their brothers," he says. "I don't want to go to my grave feeling like it was a waste."


Gunjan Sinha is a freelance writer based in Frankfurt, Germany.