While it’s true that marriage is in serious trouble in the United States, it’s not because of the gay and lesbian couples seeking to achieve it. If my own research telegraphs future marriage trends, the real peril may come from an increasing number of straight folks who have had their fill of traditional marriage. Instead of fretting about how gay couples are redefining marriage, maybe we should start talking about why straight couples are rejecting it.

At least that’s the conclusion I’m reaching in considering the fallout from Illinois’ first-in-the-nation experiment with civil unions for opposite-sex couples, which went into effect June 1 of last year. When asked during a long Skype interview why she and her partner, Justin Gates, chose to enter a civil union rather than marry, Leah Whitesel, who identifies as queer despite her current relationship, framed the question this way: “Gay marriage doesn’t seem like the right discussion to me. Because it should be: ‘What is this institution of marriage and does it still need to be defined the way it has been?’ ” For Whitesel and Gates, the answer is no.

Many of the other straight civil union pioneers have also said no to marriage—for themselves and as an institution. The evidence is in a report that the Cook County Clerk’s Office recently issued on the nation’s first opposite-sex couples who civilly united. It found dissatisfaction with the institution of marriage because of concerns with its historical assignment of roles, its connection to religion, and its unfairness to gay and lesbian couples. My own interviews with some of these same couples, who have rejected marriage and plunged into the shallower, murkier pool of the civil union, reflect a cohort prepared to take the wrecking ball to marriage itself.

To be sure, the numbers of people entering opposite-sex civil unions in Illinois still represents a very small share of the total. As of Dec. 29, 2011, only 148 of the 1,993 civil union licenses had gone to opposite-sex couples. That’s not surprising, because—as is the case in the other states that have recognized civil unions—the Illinois measure was primarily intended to grant same-sex couples the benefits of marriage without the name. The law can’t achieve equality for them, so there’s very little about these clever creatures of compromise to attract opposite-sex couples. Civil unions aren’t recognized on the federal level, and hardly anyone understands what they are in the first place. For many same-sex couples, a civil-union law is much better than nothing. The expectation was that for opposite-sex couples, it would still be worse than the alternative. That’s why most states haven’t bothered extending the option to straight couples. And why it’s striking that some straight couples in Illinois have nevertheless opted in.

Those 148 couples might portend something big. The clerk’s office was able to survey one partner from more than half (46 of 87) of the opposite-sex couples who had civilly united as of Sept. 19. And their reasons for entering into civil unions rather than marriage should worry marriage traditionalists. For instance, by more than three-to-one, respondents cited “personal or religious convictions against marriage” as a reason for choosing the civil union. And when asked an open-ended question—“Why did you decide to obtain a civil union instead of getting married?” the most frequently proffered response fell into the political/ideological category. The report provides a few specifics behind that political objection to marriage, including statements of “solidarity with the gay community and/or support of equality, fairness, and inclusiveness.” Some respondents cited commitment/label issues, which included those who did not want a “husband” or a “wife,” or even the “marriage” label itself. And 9 percent of respondents cited religious issues. (Even though religion need not be a part of a marriage ceremony, for many the two are inextricably linked).

Almost half the respondents’ objections are loosely about their perceived objections to the institution of marriage. And only four of the 46 admitted choosing civil union status in order to preserve social security or other benefits from a previous spouse that would be lost through remarriage—but not through entering into a civil union, which isn’t federally recognized.

My own interviews were even more revealing. The couples who agreed to chat had clearly spent some time thinking about the meaning of marriage, and decided they wanted nothing to do with it. In most other ways they were fairly mainstream—even Whitesel, 32, the most politically radical of the group, isn’t exactly throwing fireballs. A non-practicing lawyer, she teaches high school civics. Gates, 30, is a computer guy and comes from what he described as a conservative religious background. The civil union status, he said, “keeps me from falling into any preconditioned behavior that I might have picked up. Calling [Leah] my partner, not my wife, helps me not to have any assumptions” or buy into traditional patterns.

Both supported the rights of gays and lesbians to marry, and their civil union was meant to express solidarity with their friends who can’t.

Toward the end of the conversation, Whitesel revealed that she’s pregnant. The same revelation came during my discussion with Alex Rifman, 32, and Jennifer Tweeton, 35. Rifman is an engineer with AT&T, who was born in Moscow and emigrated with his family to the U.S. at age 9. Tweeton, like Whitesel, has a law degree and works for the Chicago Mercantile Exchange. The couple is raising the 15-year-old son of Tweeton’s from an early marriage.

Their civil union ceremony, Tweeton said, “taught everyone there something” about the law, and the couple see themselves as involved in a teaching mission in other ways, too: “I feel like we don’t value the families that choose to be families without being married. The civil union was a way to honor that … a way to demonstrate to others” that these other family structures deserve respect, too. And Rifman, like Whitesel and Gates, thought that the civil union choice expressed solidarity with his gay and lesbian friends: “Until marriage is an option for everyone, it shouldn’t be an option for us.”

Pioneer status has its costs, though; costs familiar to many same-sex couples, who will see their own experiences reflected in the stories these couples tell. Tweeton said that her family, traditional Lutherans, didn’t see her union as “real”; they don’t treat it like a marriage. And no one’s yet mustered the courage to come out about the civil union to Tweeton’s grandmother, who’s 100 years old and “very conservative.” Even the clerk who processed their application tried to dissuade them, urging that they “should just get married,” and reminding them that “the license cost was the same.” She also insisted that Alex, as the male, be “Partner A,” even though nothing in the civil union license form contains any such requirement.

Jeff Moyers, 44, and Melissa Mizwa, 32, had a similar experience with the judge who performed the ceremony. (“Wait a minute. A civil union? This can’t be right.”) Jeff, who described himself as “the world’s worst wine salesman,” said he objected to what he perceived as the built-in religious aspect of marriage, but added, that “if push came to shove, solidarity with gays is the biggest reason” for his choosing civil union status.

Civil unions, once seen as a way station between nonrecognition of gay and lesbian relationships and full marriage equality, may turn out to be more interesting than their origin in compromise might have predicted. In the case of same-sex couples, civil unions end up underscoring the point that committed gay and lesbian relationships are less than straight ones. As the Massachusetts Supreme Court stated in a 2004 opinion, calling gay and lesbian unions civil unions rather than marriage is a “considered choice of language that reflects a demonstrable assigning of same-sex, largely homosexual, couples to second-class status.”

And now opposite-sex couples in Illinois (and soon Hawaii, where a similar law went into effect on Sunday) who choose civil union are furthering the project of marriage deconstruction. For now, their numbers will probably remain small. But their impact could be much greater, by expanding the already lively national conversation about what marriage really means and whether it’s something we need to be fighting to preserve.