More adventures in the "My genes made me do it" department, this time, marital infidelity. Researchers at the Karolinska Institute, in Stockholm, have concluded that men with that men with two copies of a particular gene variant are less likely than men without it to be engaged in happy monogamous relationships. Just over one-third of the men with two copies of the gene variant had marital difficulties, but only 15% of the men with no copies exhibited such difficulties. The gene in question regulates levels of the hormone vasopressin. Studies have shown that this turns highly promiscuous male meadow voles into model monogamous husbands.

The researchers reached the cautious conclusion that "previous studies on the influence of the gene coding for the vasopressin receptor on pair-bonding in voles are probably of relevance also for humans."

The media always find news of an "infidelity gene" exciting. In 2004, a British researcher claimed that some women may be genetically programmed to stray in their relationships. In a study of twins, he found that if one had a history of infidelity, the chances her sister would also stray were about 55%.

However, Erik Parens, of The Hastings Center, an American bioethics institute poured cold water on these suggestions. "First, it's possible to have the gene variant but to have no marital difficulties. (66 percent of the men with two copies of the variant had no marital trouble.) Second, it's possible to have marital difficulties but not have the gene variant. (Again, 15 percent of the men with no copies of the variant did have trouble.)" The weak results of this study, he argues, show that the One-Gene-One-Disorder (or O GOD) model of human behavior has been discredited. ~ San Francisco Chronicle, Sept 10; London Times, Sept 2