In voles, a polymorphism in the gene that encodes vasopressin receptor 1a is associated with variations in promiscuity: monogamous prairy voles have one receptor variant, whereas polygamous montane voles have another. A study in PNAS recently reported that a polymorphism in this gene also influences how human males fare in relationships with their partners.

Women who are married to men with one particular variant of the gene reported “...lower scores on levels of marital quality than women married to men not carrying this variant...”, says study author Hasse Walum of the Karolinska Institute in Sweden ( Washington Post , 2 September 2008). Moreover, “Men with two copies of [this] allele had twice the risk of experiencing marital dysfunction, with a threat of divorce during the year [preceding the study]”, Wallum says (Washington Post).

Larry Young, a social neurobiologist at Emory University in Atlanta, USA, says: “...it's very intriguing that the same gene that is involved in pair bonding in a little rodent could be affecting our own relationships.” ( NPR , 2 September 2008.) According to George Fieldman, a psychology lecturer at Buckinghamshire New University in the UK, there could be an evolutionary benefit to carrying the polymorphism “...if the objective is to survive and spread your genes.” ( BBC News , 2 September 2008.)

Unsurprisingly, the story generated a lot of media interest, and even talk of a “divorce gene” ( Telegraph , 1 September 2008). However, Wallum made it clear that the gene effect is small and that “...it can not, with any real accuracy, be used to predict how someone will behave.” (Washington Post.) Indeed, “No one is saying biology is destiny”, says anthropologist Helen Fisher of Rutgers University, but “Knowing there are biological weak links can help you overcome them.” (Washington Post.)