Under these conditions, it made no sense for men or women whose affections inclined to their own sex to complain that it was unfair not to allow them to marry for love. They were more likely to do what so many heterosexuals did—marry for convenience and keep their loved one on the side.

For millennia, heterosexual marriage was also much more about enforcing social and gender hierarchies than protecting children and nourishing the well-being of all family members. Marriage was an authority relationship rather than a love one. In medieval Europe, and in the New England colonies of America, disobedience by wives or children was conceptualized as a lesser form of treason.

Throughout the pre-modern period, European and American husbands had the right to physically restrain, imprison, and "punish" their wives as well as their children. Not until the 1860s did several state courts in the United States begin to rule that a man did not have the right to physically discipline his wife. Only in 1897 did the highest court in Britain rule that a man did not have the right to deprive another British citizen of her liberty by locking her up, even if she was his wife.

English common law, which was adopted in America and regulated marriage law until the late 19th century, held that a woman's identity was subsumed in her husband's upon marriage. Marriage gave the husband sole ownership over all property a wife brought to marriage and any income she earned while in it.  A man could make no contract with his wife, nor cede her anything, said the jurists, "for that would presume her independent existence." As late as 1863, a New York court warned that giving wives independent property rights would "sow the seeds of perpetual discord," potentially dooming marriage.    

Even after legislators rejected the doctrine that a wife's existence was subsumed in the person of her husband, the principle that marriage was a hierarchical relationship was retained in the "head and master" laws that remained on the books in many European countries and American states until the 1970s. These gave the husband the right to determine the use of community property, to decide whether his wife could take a job, and to choose the couple's place of residence.

Marriage and Children

Opponents of same-sex marriage often claim that marriage was invented "to make sure that every child had the protection of a father and a mother," and that legalizing same sex marriage would undermine this traditional function of marriage. But in every past society that had a strong institution of marriage, the flip side was an equally strong tradition of illegitimacy, which allowed family patriarchs and political authorities to deny many children access to family property and parental protection.

In Anglo-American law, a child born outside an approved marriage was a "fillius nullius"—a child of no one, entitled to nothing. Each year, thousands of such children were abandoned—often to death—in towns and villages in every country of Europe.

If a well-to-do father could be identified, he was seldom obliged to support his child. Even the relationship between mother and child was tenuous. In the United States, until the late 1960s, a child born out of wedlock was not entitled to collect debts owed to his mother or to inherit from his mother's parents if she predeceased them.

Throughout most of the past, even legally-recognized wives and children received few of the protections we now associate with marriage. Parents put their children to work to accumulate resources for their own old age, enforcing their will by periodic beatings. They had the right to disinherit a disobedient child.

Making Marriage Modern:  Love, Sex, Rights, and Gender Roles

The first step in the process of overturning traditional heterosexual marriage came just 250 years ago, when the idea emerged during the Enlightenment and the Age of Revolution that free choice based on love and compatibility should be the basis for mate selection. As the Declaration of Independence famously put it, people were now supposed to have a right to "the pursuit of happiness."

Social conservatives were appalled by the radical notion that young people should be able to choose their own mates, and should do so on the basis of sentiment rather than practicality. They warned that all sorts of unintended consequences could ensue if happiness and love were to become part of the definition of marriage.

And they were right. As soon as love became a central purpose of marriage, individuals began to agitate for the right to leave a loveless marriage, or to refuse to enter one. And although no one yet demanded same-sex marriage, many began to object to the criminalization of same-sex love. Revolutionary France and two other nations repealed their anti-sodomy laws on the basis that the state should not penalize the private choices of consenting adults.

But it did not occur to most people that individuals who loved someone of the same sex should be allowed to marry, because the gendered definition of marriage remained intact. Husbands and wives continued to be assigned very separate and distinct roles by law and cultural pressure.

Indeed, the emergence of the love match in the late 18th century actually increased the differences between husbands and wives. Marriage was redefined as a union of two people whose love was based on the fact that they were opposites. Men and women were increasingly described as having entirely different social roles, physical capacities, and emotional orientations. By the 19th century, males were defined more strictly as breadwinners than in the past, while females were redefined as domestic and largely asexual beings.

The Victorian version of the love marriage inhibited gays and lesbians from demanding access to the institution because sexual desire was not considered to be a primary motive for marriage or even an important part of marital satisfaction.

But in the early 20th century a new ideal developed that marriage should be based not just on love but on mutual sexual attraction and satisfaction. Contradicting Victorian conventions, marital advisors now argued that "a satisfying sex life" was "essential" to a good marriage.

This validation of sexuality as a major component of a successful marriage was the second stage of the revolution in traditional marriage. Some people began to argue that if love was based on sexual attraction and satisfaction, the laws and prejudices against homosexual relationships should be rethought. Homosexual subcultures blossomed in the 1920s, as people came to see sexual desire as a central part of a person's identity. Lesbians in Harlem even organized huge mass weddings.

But most early proponents of gay and lesbian rights still did not demand legal access to marriage, partly because many rejected the gender conventions on which heterosexual marriage was based, and also partly because few people yet believed that there was such a thing as an individual right to marry, even for heterosexuals.

In the 1920s, 38 states had laws prohibiting whites from marrying Blacks, Mulattos, Japanese, Chinese, Indians, Mongolians, Malays, or Filipinos. Twelve states forbade marriage to a "drunk" or a "mental defective."  Prisoners did not have a right to marry, and some employers routinely fired workers who got married.

Individual choice was even more limited when it came to leaving a marriage. The state still held fast to its prerogative to define the acceptable grounds for divorce. In fact, the laws allowed judges to refuse a couple's petition for divorce even if both partners desired it.

So a third stage in the revolutionizing of heterosexual marriage came when courts began to uphold marriage as an individual right, equal access to which could not be prohibited by government or employers.

In 1967 the Supreme Court ruled that states could not forbid interracial marriage. Soon thereafter, it struck down provisions preventing prisoners from marrying and denied employers such as airlines the right to fire employees when they married. By the late 1960s, legislatures and courts had also begun to support the right of couples to decide whether or not they wanted to divorce, regardless of what authorities might deem a valid or moral reason for parting.

Almost immediately, some gays and lesbians suggested that if society was going to grant heterosexuals the right to make marital decisions, even when a majority of the population disapproved of those choices—as was still true of interracial marriage—the same right ought to be extended to them.

Simultaneously, heterosexual marriage was becoming increasingly separated from the goal of procreation. In 1965, the Supreme Court ruled that the government could not deny a married couple the right to practice birth control. By the 1970s, many heterosexual couples were stating openly that they were "childless by choice," and even claiming that their marriages were all the better for it.

On the other side of the coin, advances in assisted reproduction from the 1970s further undermined the procreative conception of marriage, allowing two people who were physically incapable of reproducing through having sex together to do so by other means, with the offspring counted as legitimate.

During the 1950s and the 1960s, these changes gradually encouraged more members of the gay and lesbian community to demand access to marriage. If marriage was supposed to be based on love, sexuality, and human rights—and if procreation was not essential to marriage—what prevented gays and lesbians from marrying? If every child needed a father and mother, how come society now allowed couples with children to divorce, and no longer penalized unwed motherhood?

Only one cultural assumption now stood in the way of the claim that same-sex couples should be entitled to marry. This was the belief that marriage had to be based on a division of labor by gender. On May 18, 1970, two men in Minnesota filed for a marriage license and several other couples around the country soon followed suit. As the Minnesota couple was leaving the county clerk's office, a reporter asked them which one was going to be the wife. "We don't play those kinds of roles" was the reply. Few heterosexual Americans could then imagine how marriage could exist if no one played the role of a husband or a wife.

During the 1970s, courts continued to rule—and most Americans continued to believe—that husbands and wives had different duties within marriage. The husband, but not the wife, was required to support the family financially. The wife, but not the husband, was supposed to provide services in and around the home. That is why a man could sue for loss of consortium if his wife were killed or incapacitated, but a wife could not. It is also why the concept of marital rape was considered a contradiction in terms.

But toward the end of the 1970s and during the 1980s, another revolutionary innovation in marriage—as momentous as the acceptance of the love-based marriage 250 years ago—was instituted. American states and European countries repealed their "head and master" laws and rewrote legal codes so that they no longer ascribed different responsibilities and rights to husband and wife.

This final change, eliminating prescribed gender roles, made heterosexual marriage fairer and more egalitarian than ever before. But it also made marriage an institution that gays and lesbians could feel free to claim as their own—particularly since marriage still involved important economic aspects (such as inheritance, health benefits, taxation benefits, etc.) from which same-sex couples were excluded.

The Marriage Revolution

Thus, it was heterosexuals who turned marriage into a voluntary love relationship rather than a mandatory economic and political institution. Heterosexuals were the ones who made procreation voluntary, so that some couples could choose childlessness. Heterosexuals also pioneered and legalized the turn to assisted reproduction, so that even couples who could not "naturally" have kids could become parents. And finally, heterosexuals subverted the long-standing rule that every marriage had to have a husband who played one role in the family and a wife who played a completely different one.

In their demand to be married, gays and lesbians have simply looked at the revolution wrought by heterosexuals and pointed out that these new norms of marriage now apply to them too.

More about the author

For more on the history of marriage by Stephanie Coontz, please see Marriage, A History: From Obedience to Intimacy, or How Love Conquered Marriage, (Viking Press, 2005), The Way We Never Were: American Families and the Nostalgia Trap (1992 and 2000, Basic Books).