In mounting their defense, advocates of same-sex marriage have argued that gays and lesbians who wish to marry are committed to family well-being; that concern for children’s welfare is a chief reason many do want to marry; that gay people are being discriminated against, as a class, in being denied rights readily available to any heterosexual. And to the charge that same-sex marriage will change marriage, they tend to argue that it will not—that married gays and lesbians will blend seamlessly with the millions of married straight Americans. “The notion that this group can somehow fundamentally change the institution of marriage—I find it difficult to wrap my head around,” says Gary Gates, a demographer with the Williams Institute, a research center affiliated with the UCLA School of Law.

But what if the critics are correct, just not in the way they suppose? What if same-sex marriage does change marriage, but primarily for the better? For one thing, there is reason to think that, rather than making marriage more fragile, the boom of publicity around same-sex weddings could awaken among heterosexuals a new interest in the institution, at least for a time. But the larger change might be this: by providing a new model of how two people can live together equitably, same-sex marriage could help haul matrimony more fully into the 21st century. Although marriage is in many ways fairer and more pleasurable for both men and women than it once was, it hasn’t entirely thrown off old notions and habits. As a result, many men and women enter into it burdened with assumptions and stereotypes that create stress and resentment. Others, confronted with these increasingly anachronistic expectations—expectations at odds with the economic and practical realities of their own lives—don’t enter into it at all.

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!”

Beyond that, 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. For instance: we know that heterosexual wives are more likely than husbands to initiate divorce. Social scientists have struggled to explain the discrepancy, variously attributing it to the sexual revolution; to women’s financial independence; to men’s failure to keep modern wives happy. Intriguingly, in Norway and Sweden, where registered partnerships for same-sex couples have been in place for about two decades (full-fledged marriage was introduced several years ago), research has found that lesbians are twice as likely as gay men to split up. If women become dissatisfied even when married to other women, maybe the problem with marriage isn’t men. Maybe women are too particular. Maybe even women don’t know what women want. These are the kinds of things that we will be able to tease out.