The XX Factor: Slate women blog about politics, etc...

But Serially, Folks ...

All right, Tim Noah, I will bite.

"What makes married women want to have affairs?" you ask?

The same things that make married men want to have affairs (excepting, of course, the desire to "spread seed").

Monogamy is hard. For all of us. It's unrealistic for people who live as long as humans do today. We, too, crave variety. We, too, have fantasies. We, too, are busy, overworked, have too many responsibilities, and want to blow off some steam. Some of us are neglected, abused, oppressed, unloved, ignored, deprived of affection, unhappy, unfulfilled. Some of us are just bored. Some of us are just horny. Some of us are getting old and we want to feel young and sexy again.

Some of us have been brainwashed by the Jane Austen fantasy, and we are still looking for Mr. Darcy.

Some of us love our husbands, but, well, we are married, not dead. There are a lot of hot, tempting women in the world, but there are a lot of hot, tempting men, as well, and we are exposed to their hot, tempting images everywhere, every day, all the time. (Note to Jonathan Rhys Meyers: Call me!)

I suspect there are as many reasons women want to have affairs as there are women having affairs.

I find it curious that so many people still buy into the myth that pairing off and staying together forever is the only model of a successful relationship. It's hard not to acquiesce to this religion-enforced, society-sanctioned, government-rewarded "lifestyle."

But as our rates of infidelity and divorce suggest, it's not realistic. This is not to say that we should live in a sexual free-for-all. There are great rewards that come with being in an emotionally, as well as sexually, intimate relationship. We do seem to naturally pair off, for a while, and have relationships this way—but serially. I think serial monogamy is perhaps more realistic, though it is also more complicated.

The problem is, how long is "for a while"? How long should it be? Seven minutes or 70 years?