I came across an interesting newspaper article linking a gene variant in men to  their level of maritial faithfulness.

(Segments as quoted from The Washington Post, Sept. 2, 2008)
It says men are more likely to be devoted and loyal husbands when they lack a particular variant of a gene that influences brain activity. 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.

The finding sets off a debate about whether people should conduct genetic tests to find out whether potential mates are bad marriage prospects. Several independent scientists called the discovery remarkable and elegant but disagreed over whether such information ought to be used in making personal decisions about love and marriage.

The studies focused on two species that look nearly alike: prairie voles and montane voles. The first time a male prairie vole mates with a female, he forms a bond with her for life, breeding and raising successive litters. Male montane voles think of sex as a series of one-night stands; they are loners and do not bond with females or help raise offspring.

No one knows for sure whether the same mechanism is at work in humans. Although humans are evolutionarily distant from voles, there are many examples in nature that show that the action of genes is conserved across distantly related species.

I had to look up what a vole is:
The adult prairie vole is a small rodent with a stocky and stubby body, short tail, and four short legs. The eyes and ears are small.

Is your man a prairie vole or montane vole?

Amazing. What happened to the gene that says we can intelligently reason and make a choice to remain faithful in marriage?