"The monogamy gene"?

Maybe you've seen the breathless news coverage of the "monogamy gene" that researchers in Sweden have supposedly found. The gene affects receptors of vasopressin in the brain. Vasopressin is one of the famous hormones (along with dopamine, oxytocin, and phenylethylamine, PEA) that are involved in falling in love, limerence, NRE, and bonding behavior in both humans and animals. In a sample of 552 Swedish couples, men who had the genetic culprit were more likely to have colder, conflict-prone marriages and to show other signs of poor relationship behavior.

What the reseachers actually seem to have found is a gene that affects bonding, not necessarily a "monogamy gene." It's being called that because monogamy is the only type of intimate, committed sexual bonding that the news media grasp.

Here's a hypothesis: Test people living in triads and quads for the gene, and I have a hunch that they'll score unusually low for the problem genetic trait, rather than unusually high as people might naively expect.

Hey researchers, here's a project! Not just because it might tell interesting things about polys, but because it would refine the actual effect of the gene and its vasopressin mechanism. Does lack of the gene promote successful monogamy directly? Or does it merely promote intimate connections generally?...including the polyamorous generalization of couple-love into something wider. Polys would be a tool to split that difference in the gene's effect.

Here's a good, clear article on the findings from the Washington Post:

Men are more likely to be devoted and loyal husbands when they lack a particular variant of a gene that influences brain activity, researchers announced yesterday — the first time that science has shown a direct link between a man's genes and his aptitude for monogamy.

The finding is striking because it not only links the gene variant — which is present in two of every five men — with the risk of marital discord and divorce, but also appears to predict whether women involved with these men are likely to say their partners are emotionally close and available, or distant and disagreeable. The presence of the gene variant, or allele, also seems predictive of whether men get married or live with women without getting married.

"Men with two copies of the allele had twice the risk of experiencing marital dysfunction, with a threat of divorce during the last year, compared to men carrying one or no copies," said Hasse Walum, a behavioral geneticist at the Karolinska Institute in Stockholm who led the study. "Women married to men with one or two copies of the allele scored lower on average on how satisfied they were with the relationship compared to women married to men with no copies."

The scientists studied men because the hormone being examined is known to play a larger role in their brains than in women's brains....

Walum said that... the study is the latest piece of evidence to show that biology — down to the level of individual genes — can play a powerful role in shaping complex human behavior.

The allele... regulates the activity of a hormone in the brain known as vasopressin. It dictates how and where vasopressin receptors are situated in the brain. Effectively, said Larry J. Young, a psychiatrist who studies the genetics of social behavior at Emory University, brain receptors act like locks, and vasopressin acts like a key. The key works only when there is a lock; in the absence of a receptor, vasopressin cannot act.

All the scientists emphasized that more work needs to be done to replicate the finding, and to explore possible interactions between multiple genes and environmental factors....

Read the whole article (Sept. 2, 2008; free registration required). If it becomes unavailable, you can read the text here.

Here's New Scientist magazine's story:

There has been speculation about the role of the hormone vasopressin in humans ever since we discovered that variations in where receptors for the hormone are expressed makes prairie voles strictly monogamous but meadow voles promiscuous; vasopressin is related to the "cuddle chemical" oxytocin. Now it seems variations in a section of the gene coding for a vasopressin receptor in people help to determine whether men are serial commitment-phobes or devoted husbands.

...Given that everyone surveyed had been in their relationship for at least five years, the team suggests that having multiple copies somehow contributes to commitment problems in men. Because the results were collected for a different study the team couldn't quiz the men on whether they were faithful, says Walum.

...Walum's colleague Paul Lichtenstein says the team's next task is to test how a nasal vasopressin spray affects altruism and jealousy.

Read the whole article (Sept. 1, 2008).

Not so fast, says Wired:

...Journalists rushed headlong into the "divorce gene." "Whether a man has one type of gene versus another could help decide whether he's good 'husband material,'" announces HealthDay News. "Marriage problems? Husband's genes may be to blame," says a Reuters headline writer. "Marital woes can often be attributed to men's genetic make-up," declares Agence-France Press....

Taking the prize for carelessness is the [London] Telegraph, who coined the term "divorce gene"....

...NPR's All Things Considered also parrots the "new excuse" line, but qualifies it well: bioethicist Erik Parens... [notes] that "it's possible to have the gene variant but not have the marital difficulties," and vice versa. "Human relationships are so complicated," Parens is paraphrased as saying, "that the effect of any one gene would be very small."

Furthermore, the study's fine print notes a previously observed and tentative link between the genetic variation and autism. Men with "bad" genes — or "bad" neural networks — might not be two-timing gigolos, but people who are bad at communicating and social interaction.

Read the whole article.

The reseachers' actual paper appears in the Proceedings of the National Academy of Sciences for Sept. 2, 2008. (To get the whole thing you have to be a subscriber or pay $10.) Here are the title, authors, and abstract:

Genetic variation in the vasopressin receptor 1a gene (AVPR1A) associates with pair-bonding behavior in humans

Hasse Walum, Lars Westberg, Susanne Henningsson, Jenae M. Neiderhiser, David Reiss, Wilmar Igl, Jody M. Ganiban, Erica L. Spotts, Nancy L. Pedersen, Elias Eriksson, and Paul Lichtenstein.

Pair-bonding has been suggested to be a critical factor in the evolutionary development of the social brain. The brain neuropeptide arginine vasopressin (AVP) exerts an important influence on pair-bonding behavior in voles. There is a strong association between a polymorphic repeat sequence in the 5′ flanking region of the gene (avpr1a) encoding one of the AVP receptor subtypes (V1aR), and proneness for monogamous behavior in males of this species. It is not yet known whether similar mechanisms are important also for human pair-bonding. Here, we report an association between one of the human AVPR1A repeat polymorphisms (RS3) and traits reflecting pair-bonding behavior in men, including partner bonding, perceived marital problems, and marital status, and show that the RS3 genotype of the males also affects marital quality as perceived by their spouses. These results suggest an association between a single gene and pair-bonding behavior in humans, and indicate that the well characterized influence of AVP on pair-bonding in voles may be of relevance also for humans.

Update Sept. 9: So it turns out that, according to recent research, the gene in question affects a whole spectrum of other human traits and behaviors — autism, memory, musical memory, eating, cooperative behavior, strategies in playing The Dictator Game, and creative dance. Here are a bunch of papers about this collected at the Gene Expression blog.

Creative dance? I dance like a crippled giraffe; is that why I'm a good poly-mono switch? Don't tell the media about this....

More update: Mark Liberman takes apart the bad science reporting and puts this interesting study into perspective here.

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