Same-sex spouses, who cannot divide their labor based on preexisting gender norms, must approach marriage differently than their heterosexual peers. From sex to fighting, from child-rearing to chores, they must hammer out every last detail of domestic life without falling back on assumptions about who will do what. In this regard, they provide an example that can be enlightening to all couples. Critics warn of an institution rendered “genderless.” But if a genderless marriage is a marriage in which the wife is not automatically expected to be responsible for school forms and child care and dinner preparation and birthday parties and midnight feedings and holiday shopping, I think it’s fair to say that many heterosexual women would cry “Bring it on!”

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Gay marriage can function as a controlled experiment, helping us see which aspects of marital difficulty are truly rooted in gender and which are not. A growing body of social science has begun to compare straight and same-sex couples in an attempt to get at the question of what is female, what is male. Some of the findings are surprising.