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.

"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."