June 16, 2004 -- Imagine turning a bed-hopping lothario into a dedicated, monogamous mate with the flip of a genetic switch. A new study shows it may be possible, at least for the notoriously promiscuous meadow mole.
Accomplishing the same feat in humans may be a bit more complicated, but researchers say they've found a gene that appears to have a profound effect on the social behavior of animals.
The gene, known as the vasopressin receptor, is located in the brain's reward center and may also be involved in drug addiction.
Researchers say the findings may help explain the neurobiology behind romantic love as well as disorders such as autism that affect how people form social bonds.
The Monogamy Gene
In the study, researchers used a harmless virus to transfer the gene from monogamous male prairie voles, who are known to form lifelong bonds with a single mate, into the brain of meadow voles, who mate with multiple partners and lack vasopressin receptors in their brain's reward center.
A few days later, the meadow voles had vasopressin receptors levels similar to those found in the prairie voles.
Researchers paired the animals with sexually receptive mates and allowed them a day to get to know each other before the males were given a fidelity test.
Each vole was allowed to wander between his first partner and a new potential mate. The study showed that both the prairie voles and the genetically modified meadow moles huddled close to their original partner while the untreated meadow voles behaved like loners and spent time by themselves.
The results appear published in the June 17 issue of Nature.
Are Animals Addicted to Love?
Researchers say previous research has shown that these vasopressin receptors may play a role in social disorders, such as autism, that make it difficult to form social bonds.
Studies in humans have also suggested that the same brain pathways involved in forming romantic relationships may also be involved in drug addiction.
"The brain process of bonding with one's partner may be similar to becoming addicted to drugs: both activate reward circuits in the brain," says researcher Miranda Lim, a postdoctoral fellow at Emory University, in a news release.
Pair bonding in humans is a much more complex process than in moles, and researchers say social, economic, historic, and individual differences all play a role.
"Our study, however, provides evidence, in a comparatively simple animal model, that changes in the activity of a single gene profoundly can change a fundamental social behavior of animals within a species," says researcher Larry J. Young, PhD, of Emory University's School of Medicine, in the release.
"It is intriguing," says Young, "to consider that individual differences in vasopressin receptors in humans might play a role in how differently people form relationships."
Researchers say fewer than 5% of mammals are monogamous by nature, and these findings may offer new clues to the genetic and biological processes behind monogamy and how humans form lifelong social bonds.
In a related essay published in the same journal, Melvin Konner, of the department of anthropology at Emory University in Atlanta, writes, "We do not yet know if a similar system helps explain male attachment in non-human primates, much less humans, but a medicine that might someday be offered to certain men is an interesting prospect.
"We are a long way from a commitment pill, but perhaps closer to a neurology of romance," writes Konner.