Of course you’re right about these things, but we’re still in the emotionless realm of the hypothetical, remember, and all else being equal, if you’re simply trying to minimize the chances of landing an adulterous partner, you might as well stack the deck in your favor by marrying the woman who “knows” that God would get really mad at her if she misappropriated her genitalia. There really is evidence from controlled experiments showing that religious thinking and church attendance leads to moral behavior.
Still, I concede that the irreducible alchemy of romance makes my cold logic rather difficult to apply to individual marriages.
Making a positive first impression on a potential mate can be as easy as dropping the words "zombie" or "atheist" into your opening salvo when using an online dating site.
Making spelling errors, being too forward, slipping into sloppy internet slang or simply mentioning "God" can doom your chances for making that crucial first connection.
A shoulder-shrugging agnostic or lukewarm “spiritual but not religious” person, for instance, would probably be able to tolerate an atheist spouse better than a dead-set Muslim could ever hope to do.
In the long run, though, such betrayal would have a negligible effect on our genetic success.
This rule of thumb, that behaviors are motivated by beliefs independent of whether or not those beliefs are true, works just as well for atheist women seeking nonphilandering husbands, and probably also for gay people looking for monogamous partners.
In the case of gays, however—and this is why I rendered myself straight in the example—the evolutionary stakes of infidelity are much lower than they are for heterosexual cheating.
If, unlike hypothetical me, it’s terribly important for your partner to share your rigorously rational worldview, then you might find a match made in heaven at one of several online dating sites catering to single atheists: Atheist Passions.com, Freethinker Match.com, and Atheist Dating (which promises you a “deity-free romance”).
Because we don't have any real data on the relative success of atheist marriages or rates of infidelity, and only a few surveys that include marriages between nonbelievers and believers as part of a much larger pool of “interfaith” couplings, we’re stuck in the land of speculation.
She may well be suffering a very bad case of the dreaded God delusion, but perhaps this isn’t such a bad thing for her atheist husband.