“In the morning, I’ve got kid duty; Amy doesn’t even see the kids,” says Isabelle Dikland. “She does pickup and makes dinner every night.” (Gail Albert Halaban)

It is more than a little ironic that gay marriage has emerged as the era’s defining civil-rights struggle even as marriage itself seems more endangered every day. Americans are waiting longer to marry: according to the U.S. Census Bureau, the median age of first marriage is 28 for men and 26 for women, up from 23 and 20, respectively, in 1950. Rates of cohabitation have risen swiftly and sharply, and more people than ever are living single. Most Americans still marry at some point, but many of those marriages end in divorce. (Although the U.S. divorce rate has declined from its all-time high in the late ’70s and early ’80s, it has remained higher than those of most European countries.) All told, this has created an unstable system of what the UCLA sociologist Suzanne Bianchi calls “partnering and repartnering,” a relentless emotional and domestic churn that sometimes results in people forgoing the institution altogether.

Though people may be waiting to marry, they are not necessarily waiting to have children. The National Center for Family and Marriage Research has produced a startling analysis of data from the Census Bureau and the Centers for Disease Control and Prevention showing that women’s median age when they have their first child is lower than their median age at first marriage. In other words, having children before you marry has become normal. College graduates enjoy relatively stable unions, but for every other group, marriage is collapsing. Among “middle American” women (those with a high-school degree or some college), an astonishing 58 percent of first-time mothers are unmarried. The old Groucho Marx joke—“I don’t care to belong to any club that will have me as a member”—applies a little differently in this context: you might well ask why gays and lesbians want to join an institution that keeps dithering about whether to admit them even as the repo men are coming for the furniture and the fire marshal is about to close down the clubhouse.

Against this backdrop, gay-marriage opponents have argued that allowing same-sex couples to wed will pretty much finish matrimony off. This point was advanced in briefs and oral arguments before the Supreme Court in March, in two major same-sex-marriage cases. One of these is a constitutional challenge to a key section of the Defense of Marriage Act, the 1996 law that defines marriage as a union between a man and a woman, and bars the federal government from recognizing same-sex marriages. The other involves California’s Proposition 8, a same-sex-marriage ban passed by voters in 2008 but overturned by a federal judge in 2010. Appearing before the high court in March, Charles J. Cooper, the lawyer defending the California ban, predicted that same-sex marriage would undermine traditional marriage by eroding “marital norms.”

The belief that gay marriage will harm marriage has roots in both religious beliefs about matrimony and secular conservative concerns about broader shifts in American life. One prominent line of thinking holds that men and women have distinct roles to play in family life; that children need both a mother and a father, preferably biologically related to them; and that a central purpose of marriage is abetting heterosexual procreation. During the Supreme Court arguments over Proposition 8, Justice Elena Kagan asked Cooper whether the essence of his argument against gay marriage was that opposite-sex couples can procreate while same-sex ones cannot. “That’s the essential thrust of our position, yes,” replied Cooper. He also warned that “redefining marriage as a genderless institution could well lead over time to harms to that institution.”

Threaded through this thinking is a related conviction that mothers and fathers should treat their union as “permanent and exclusive,” as the Princeton professor Robert P. George and his co-authors write in the new book What Is Marriage? Man and Woman: A Defense. Marriage, seen this way, is a rigid institution that exists primarily for the rearing of children and that powerfully constrains the behavior of adults (one is tempted to call this the “long slog ’til death” view of marriage), rather than an emotional union entered into for pleasure and companionship between adults. These critics of gay marriage are, quite validly, worried that too many American children are being raised in unstable homes, either by struggling single parents or by a transient succession of live-in adults. They fear that the spread of gay marriage could help finally sever the increasingly tenuous link between children and marriage, confirming that it’s okay for dads, or moms, to be deleted from family life as hedonic fulfillment dictates.

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.

In the past few years, as support for same-sex marriage has gained momentum, advocates have been able to shift their strategy away from fighting bans on it (on the books in 38 states as of this writing) and toward orchestrating popular votes in its favor. In 2012, voters in Maine, Maryland, and Washington state passed measures legalizing same-sex marriage, joining the District of Columbia and the six states that had already legalized gay marriage via legislatures or courts. Similar measures are moving forward in four other states. In the coming weeks, the high court is expected to issue its rulings on gay marriage. After oral arguments in the two cases concluded, many Court observers predicted that the part of DOMA in question might well be struck down as a federal intrusion on states’ ability to decide family law, thereby forcing the federal government to recognize the marriages of same-sex couples. As for Prop 8, any number of outcomes seem possible. The Court could decide that the case should not have been heard in the first place, given that the ban isn’t being defended by California state officials but instead by the original supporters of the initiative. Such dismissal on “standing” could have the effect of legalizing same-sex marriage in California. Alternatively, the Court could deliver a narrow ruling (whether upholding or overturning the ban) that does not apply to every state. Among other feasible, if less likely, outcomes: the Court could use Prop 8 to declare all such bans unconstitutional, legalizing gay marriage everywhere.

Whatever happens with the high court, it seems likely that gay marriage will continue its spread through the land. So what happens, then, to the institution of marriage? The impact is likely to be felt near and far, both fleetingly and more permanently, in ways confounding to partisans on both sides.

RULES FOR A MORE PERFECT UNION

Not all is broken within modern marriage, of course. On the contrary: the institution is far more flexible and forgiving than it used to be. In the wake of women’s large-scale entry into the workplace, men are less likely than they once were to be saddled with being a family’s sole breadwinner, and can carve out a life that includes the close companionship of their children. Meanwhile, women are less likely to be saddled with the sole responsibility for child care and housework, and can envision a life beyond the stove top and laundry basket.

And yet for many couples, as Bianchi, the UCLA sociologist, has pointed out, the modern ideal of egalitarianism has proved “quite difficult to realize.” Though men are carrying more of a domestic workload than in the past, women still bear the brunt of the second shift. Among couples with children, when both spouses work full-time, women do 32 hours a week of housework, child care, shopping, and other family-related services, compared with the 21 hours men put in. Men do more paid work—45 hours, compared with 39 for women—but still have more free time: 31 hours, compared with 25 for women. Betsey Stevenson and Justin Wolfers, economists and professors of public policy at the University of Michigan, have shown that happiness rates among women have dropped even as women have acquired more life options. One possible cause is the lingering inequity in male-female marriage: women’s at-home workload can become so burdensome that wives opt out of the paid workforce—or sit at the office making mental lists of the chores they do versus the chores their husbands do, and bang their heads on their desks in despair.

Not that everything is easy for fathers in dual-earner couples, who now feel afflicted by work-life conflict in even greater numbers than their wives (60 percent of men in such couples say they experience this conflict, versus 47 percent of women, according to a 2008 study by the Families and Work Institute). And men face a set of unfair expectations all their own: the Pew Research Center found in 2010 that 67 percent of Americans still believe it’s “very important” that a man be ready to support a family before getting married, while only 33 percent believe the same about women.

This burden, exacerbated by the economic realities facing many men today, has undoubtedly contributed to marriage’s recent decline. As our economy has transitioned away from manufacturing and industry, men with a high-school education can no longer expect the steady, well-paying union jobs that formerly enabled many to support their families. Outdated assumptions that men should bring something to the table, and that this something should be money, don’t help. Surveying their prospects, many working-class mothers reject marriage altogether, perhaps reasoning that they can support a child, but don’t want a dependent husband.

It’s not that people don’t want to marry. Most never-married Americans say they still aspire to marriage, but many of them see it as something grand and out of reach. Getting married is no longer something you do when you are young and foolish and starting out; prosperity is not something spouses build together. Rather, marriage has become a “marker of prestige,” as the sociologist Andrew Cherlin puts it—a capstone of a successful life, rather than its cornerstone. But while many couples have concluded that they are not ready for marriage, they have things backwards. It’s not that they aren’t ready for marriage; it’s that marriage isn’t ready for the realities of 21st-century life. Particularly for less affluent, less educated Americans, changing economic and gender realities have dismantled the old institution, without constructing any sort of replacement.

As we attempt to come up with a more functional model, research on same-sex unions can provide what Gary Gates of the Williams Institute calls an “important counterfactual.” Although gays and lesbians cannot solve all that ails marriage, they seem to be working certain things out in ways straight couples might do well to emulate, chief among them a back-to-the-drawing-board approach to divvying up marital duties. A growing body of scholarship on household division of labor shows that in many ways, same-sex couples do it better.

This scholarship got its start in the late 1960s, with a brilliant insight by the sociologist Pepper Schwartz, then a doctoral candidate at Yale. Against a backdrop of cultural upheaval—including changes at the university, which had just begun to admit female undergraduates—gender was, Schwartz says, “all we thought about.” Like many of her peers, she was keen to figure out what women were and what men were: which traits were biological and which social, and where there might be potential for transformational change. “It occurred to me,” she says, that “a naturally occurring experiment” could shed light on these issues. Actually, two experiments: the rise of unmarried heterosexual cohabitation, and the growing visibility of gay and lesbian couples. If she surveyed people in three kinds of relationships—married; straight and cohabiting; and gay and cohabiting—and all showed similarity on some measures, maybe this would say something about both men and women. If the findings didn’t line up, maybe this would say something about marriage.

After taking a teaching position at the University of Washington (where she remains a faculty member), Schwartz teamed up with a gay colleague, the late Philip Blumstein, to conduct just such a survey, zeroing in on the greater San Francisco, New York City, and Seattle metropolitan areas. It was a huge effort. Unmarried cohabiting couples were not yet easy to find, and gays and lesbians were so leery of being outed that when Schwartz asked a woman who belonged to a lesbian bridge group whether she could interview the other players about their relationships, the woman said, “We don’t even talk about it ourselves.” Schwartz and Blumstein collected responses to 12,000 questionnaires and conducted hundreds of interviews; at one point, they had 20 graduate students helping tabulate data. The project took about a decade, and resulted in a groundbreaking piece of sociology, the book American Couples: Money, Work, Sex.

What Schwartz and Blumstein found is that gay and lesbian couples were fairer in their dealings with one another than straight couples, both in intent and in practice. The lesbians in the study were almost painfully egalitarian—in some cases putting money in jars and splitting everything down to the penny in a way, Schwartz says, that “would have driven me crazy.” Many unmarried heterosexual cohabitators were also careful about divvying things up, but lesbian couples seemed to take the practice to extremes: “It was almost like ‘my kitty, your litter.’ ” Gay men, like lesbians, were more likely than straight couples to share cooking and chores. Many had been in heterosexual marriages, and when asked whether they had helped their wives with the housework in those prior unions, they usually said they had not. “You can imagine,” Schwartz says, “how irritating I found this.”

There were still some inequities: in all couples, the person with the higher income had more authority and decision-making power. This was least true for lesbians; truer for heterosexuals; and most true for gay men. Somehow, putting two men together seemed to intensify the sense that “money talks,” as Schwartz and Blumstein put it. They could not hope to determine whether this tendency was innate or social—were men naturally inclined to equate resources with power, or had our culture ingrained that idea in them?—but one way or another, the finding suggested that money was a way men competed with other men, and not just a way for husbands to compete with their wives. Among lesbians, the contested terrain lay elsewhere: for instance, interacting more with the children could be, Schwartz says, a “power move.”

Lesbians also tended to discuss things endlessly, achieving a degree of closeness unmatched by the other types of couples. Schwartz wondered whether this might account for another finding: over time, sex in lesbian relationships dwindled—a state of affairs she has described as “lesbian bed death.” (The coinage ended up on Schwartz’s Wikipedia page, to her exasperation: “There are other things that I wish I were famous around.”) She posits that lesbians may have had so much intimacy already that they didn’t need sex to get it; by contrast, heterosexual women, whose spouses were less likely to be chatty, found that “sex is a highway to intimacy.” As for men, she eventually concluded that whether they were straight or gay, they approached sex as they might a sandwich: good, bad, or mediocre, they were likely to grab it.