The biggest cheers from the record-breaking throng at the New York Pride Parade Sunday were for the soberly T-shirted, widely grinning lobbyists and activists from the coalition Marriage Equality New York. When the state legislature passed and Gov. Andrew Cuomo signed the law authorizing same-sex marriage in New York late Friday night, the number of Americans who will be able to marry same-sex partners doubled. New York is the first state to legalize same sex marriage after a dry spell following Maine’s repeal of its marriage law a year and a half ago. Maybe for lesbian and gay people, It Gets Better after all.

And they’re not the only ones. To paraphrase the great gay songwriter Stephen Sondheim: Straight women, rise! As same-sex couples marry, things get better for us, too. Remember the scary (and since-discredited) stories about how a woman is more likely to be killed by a terrorist than to find a husband after she turns 40? Or the one about how suitors are fleeing from Maureen Dowd because they’re afraid of her Pulitzer Prize? The poll showing evangelical women in patriarchal marriages are happier than Sarah Jessica Parker? Well, same-sex marriage shows that people can make long-term, loving, sexual bonds with each other even where neither is naturally inclined to tell the other what to do. Or to be the natural homemaker or the hunter-gatherer. Same-sex marriage represents the possibility that marriage can be an equal deal after all—or at least one where inequality is not locked in at birth. The conservatives are right: Same-sex marriage will change opposite-sex marriage. And it’s a good thing, too.

The people fighting same-sex marriage know this. They’ve been fighting some variation of the battle against marriage equality—for women—probably since the early Christians argued for the equality of women’s souls. In the Anglo-American common law system, laws called “coverture” eliminated women’s civic personhood when they married men. Unequal marriage was portrayed as a bargain between naturally created opposites: Women did women’s work at home, and men took care of their public role, making contracts for them and voting in their interests. Apparently unsatisfied with this “bargain,” women pressed for equality, including marriage equality, ultimately giving rise to the suffrage movement in the 19th century and feminism in the 20th.

At each point along the road to women’s equality, conservatives defended heterosexual marriage inequality on the grounds that women were naturally suited only for certain kinds of lives. At the height of the suffrage battle in 1873, the Supreme Court rejected feminist Myra Bradwell’s plea to be allowed to practice law on the grounds that “the paramount destiny and mission of woman are to fulfill the noble and benign offices of wife and mother.” In 2001, after the second wave of feminism broke, conservative scholar William Bennett wrote in his ominously titled The Broken Hearth: Reversing the Moral Collapse of the American Family: “In the past husbands and wives had well defined roles. Today, thanks to the social and sexual revolution of our time, definitions blur, and disappointed hopes can turn rapidly into hopes abandoned.”

The naturalism argument has suffered somewhat from the fact that women have been living outside their natural boundaries for decades. So marriage-equality resisters have moved to a kind of happiness project—trying to show that women with traditional gender attitudes are happier than their counterparts in more socially egalitarian relationships. In his much-debated 2006 article “What’s Love Got To Do With It? Equality, Equity, Commitment and Women’s Marital Quality” (PDF), W. Bradford Wilcox, a sociologist at the University of Virginia and resident scholar at the Institute for American Values, argued that “women are not happier in marriages marked by egalitarian practices and beliefs.” And it’s their fault: “We suspect that higher expectations of intimacy and equality among women, especially more egalitarian-minded women, have led them to view their husbands’ emotion work more critically; we also suspect that these expectations have increased marital conflict and—in turn—dampened men’s marital emotion work.” More church attendance, higher male earnings, and lower female expectations are instead the key to family happiness, Wilcox concludes.

Opponents of heterosexual equality may have been first alerted to the dangerous possibilities of same-sex marriage by a 1993 Hawaii court decision. Writing against same-sex marriage in the Washington Post in 1996, Bennett opined “Marriage is not an arbitrary construct; it is an ‘honorable estate’ based on the different, complementary nature of men and women” (italics mine). The members of Congress who drafted the federal law rejecting same-sex marriage, the Defense of Marriage Act, dropped Bennett’s article right into the Congressional Record. Seventeen years later, when the time came for the defenders of California’s same-sex marriage prohibition, Proposition 8, to produce an expert witness on the harm such unions might produce, up popped David Blankenhorn, founder and president of Brad Wilcox’s scholarly home away from home, the Institute for American Values. Who knows what same-sex marriage might do to the rest of our marriages, Blankenhorn intoned. Who knows? It might even make them more equal.

Turnabout is fair play. As the arguments for heterosexual marriage inequality were used to fight same-sex marriage, so the success of same-sex marriage is a living refutation of the argument that marriage requires congenital natural inequality with women on the bottom. Even the campaign for same-sex marriage, consisting of a torrent of moving stories about the happy same-sex couples who want to get married, is a feminist windfall. Maybe marital equality and happiness aren’t so incompatible after all.