When the Supreme Court in two separate rulings in June established a basis for state legislatures and electorates to decide whether marriage between two people of the same gender were legal  or not, all hell did not in fact break loose. Both before and after the ruling, some prominent opponents to so-called "same-sex marriage," came over to the other side.
These former opponents say that the institution of marriage is a foundational element in society dating back thousands of years, if not longer, and preserving it by extending its franchise is a better plan than forcing people to value the family unit less. Others, of course, continue to oppose same-sex marriage, often citing the same traditions and longevity.
As someone in a same-sex relationship, I followed arguments for and against the overturn of DOMA with some interest. As a medievalist, my attention was particularly caught by arguments against DOMA on Twitter and elsewhere that asserted that Christianity and history unilaterally agreed that marriage means one woman and one man and coitus. This simply isn't historically accurate even within the context of Christianity and European history.
Let me take you on a millennia-long walk down the aisle. The modern notion of marriage is connected with the historical, traditional model that those opposed to marriage equality like to cite, but it's not nearly as clean a connection as parties on either side of the same-sex marriage divide would like to claim. It is in fact, varied, changeable, and chaotic.
It's about the sacrament
In the very early history of the Christian church, the church wasn't very interested in marriage. It was, after all, existing in the midst of thriving Roman and Jewish religious beliefs, and consequently had larger concerns than marriage. Officially the church preferred a life of celibacy and virginity for all Christians.  Marriage was a compromise at best, because, as Paul put it, it was "better to marry than to burn" with passion (1 Corinthians 7:9).
For those outside of the church and non-Christians, the desire to consolidate property and find a proper work partner were driving forces behind marriage. Families took an active interest in finding spouses for their children. The paternal head of the family generally approved and selected brides and paid a bride price or dower to the bride's father, a practice that lends itself to describing this kind of marriage as a purchase marriage.
For the Romans in the early Christian era, marriage was a civil matter, based either on two free adults living together or a formal contract regarding property and inheritance. Cicero in De Oratore 3.133 provides a list of business matters in which one might consult a professional and includes purchasing a farm, best practices for agricultural success, and selecting a husband for a daughter.
For Jews, marriage was a matter of contracts and agreements between parents, and the sign of adult independence. Historically, Jewish law sanctioned fairly simple divorce and both polygyny and concubines to the extent that King Solomon is said to have 300 wives of royal birth, and 700 concubines (1 Kings 11:3). In the case of Solomon, marrying the daughters of neighboring kings was good politics, and polygyny made that possible in abundance. 
Because marriage cemented social and business connections between families, it wasn't uncommon for daughters to be married off with an eye to enhancing family connections (or making peace) without their consent, even when the participants were Christian. Since local customs often defined marriage in terms of the couple living together and engaging in sex, bridal abduction, wherein the bride to be was simply kidnapped, with or without her consent, and forcibly married, was fairly common.
For most of the middle ages, marriage was a secular, civil issue, and did not involve the church, or clergy.  It wasn't until Gratian's Decretum (ca. 1140) that canon law required both participants to verbally consent to a marriage or it would not be recognized by the church. 
By the end of the 12th century, the Western Christian (and Catholic) church established that a marriage recognized by the Church required two consenting participants and a betrothal publicly announced in advance. On the agreed upon date, the participants would be met at the church door by the priest who would verify their mutual consent, and that there was no reason to deny them marriage, and then lead the wedding party into the church for Mass and possibly, a marriage blessing. The Mass was sacred; the marriage itself took place in front of the church as an indication that it was essentially secular, a public witness of a civic ceremony. 
It wasn't until the Council of Trent in 1547 that canon law specifically named marriage unilaterally (and retroactively) as one of the seven holy sacraments in canon law. The wedding itself was still a civil and secular matter; only the sacramental nature of marriage (and the genetic relationships of the participants) were the concern of the church. 
It's about who can marry
Both religious and secular laws regarding who could and could not marry have constantly evolved. Biblical Jewish levirate laws required a brother to marry his deceased brother's childless widow, at some points making it mandatory (Deuteronomy 25:5) and slightly later, forbidding it (Leviticus 20:21). Historically marriage laws have changed based on the requirements of society. When there were lots of women and fewer men, men were encouraged to wed their brothers' widows to provide protection for the widows and an heir for the brother's property.
The Christian Church created complicated charts and rules about marriage and consanguinity (the generational distance required for the Church to acknowledge a marriage) and affinity (which relatives by marriage could and could not marry), but revised them based on current requirements, and the needs of wealthy patrons. In the 14th century most European nations created statutes about who could marry, since marriage affected inheritance, and inheritance affected who could rule. While the church in Rome was still debating the marriageability of cousins and in-laws, the English Statutes of Kilkenny in 1366 made it illegal for any native Irish to marry an English person, no matter what the church said. This had the effect of controlling access to estates and land and keeping them out of the hands of the native Irish.
Political expediency played a part in terms of law and marriage historically; when Arthur, Prince of Wales died in 1502, his widow Catherine of Aragon was married in 1503 to her brother-in-law, Arthur's younger brother Henry, subsequently Henry VIII. The marriage required papal dispensation for violating canon law regarding consanguinity, but what's the point of being rich and powerful if you can't get special dispensation? In Henry VIII's case, once he named himself head of the English church he could marry, divorce, and behead his wives with impunity.
In the United States, many states enacted laws specifically disallowing marriages between slaves as well as forbidding so-called "mixed race" marriages. Slaves might be married to each other via a ceremony with clergy officiating or in secular fashion by "jumping the broom," but neither marriage had force in law. It wasn't uncommon for slave owners to sell family members, separating parents, children and siblings. Interracial marriage wasn't legal in all states until 1967 when the Supreme court in Loving v. Virginia made it legal for interracial couples to be married in all 50 states and the District of Columbia.  In the unanimous decision by the Supreme Court, Chief Justice Earl Warren's asserted that:
Marriage is one of the "basic civil rights of man," fundamental to our very existence and survival… To deny this fundamental freedom on so unsupportable a basis as the racial classifications embodied in these statutes, classifications so directly subversive of the principle of equality at the heart of the Fourteenth Amendment . . . The Fourteenth Amendment requires that the freedom of choice to marry not be restricted by invidious racial discrimination.
The same provisions of the 14th Amendment that necessitated declaring laws against interracial marriages unconstitutional are at play in terms of the current pending same-sex cases before the Supreme Court.
It's about the children
One of the objections against the overturn of DOMA (and California's Proposition 8), is the assertion that "marriage is about having children who need a mother and a father." The emphasis on marriage primarily as a mean of engendering children is an ahistoric assertion. For one thing, marriage is not a biological requirement for engendering offspring. There are large numbers of heterosexual couples who choose not to have children, or who can't have children for a variety of reasons.
Many children are raised by a single parent quite successfully, and in the case of abuse from a disenfranchised parent, more happily. Many children have been raised by heterosexual couples who have chosen not to marry each other. Many children have been raised quite successfully by same-sex couples. Indeed, there's research documenting the success of same-sex couples as parents. 
This particular objection to same-sex marriage in the context of children and parents is grounded in assumptions about the nature of marriage and gender roles within marriage; that is, it is as much about a father and a mother as it is about a husband and a wife and based on preconceived assumptions about the gender roles and cultural obligations of each. These too have evolved.
For instance, one of the principles concepts about marriage in medieval European law codes was the concept of coverture; on marriage a man was considered to be an independent adult. A woman, even one who had had an independent trade and property of her own before marriage, became a feme covert, a woman under coverage of a man's identity and without any legal standing of her own. She could not buy or sell in her own name or sign a contract. 
The colonists who settled America retained the concept of coverture and it remained part of U.S. law until the beginning of the twentieth century.  By the late 1700s and the American Revolution, America like France was changing its views regarding marriage. Betrothals begin to be described as "love matches," and while prospective fiancé's still inquired about the "marriage portion," an increasing emphasis began to be placed on affection, if not love, and marriage as a special privileged relationship between two people rather than the economic union of two families with the husband as the CEO.
As currency use dominated commerce instead of barter, wages became crucial. Men tended to be the wage earners after marriage, even if their wives had been wage earners previously. The amount of physical labor required to run a household meant earning a wage in addition to household work and childcare simply wasn't practical for most women. Because it didn't result in pay, "woman's work" was slowly, silently devalued. What had been valued as household management became "homemaking," perceived as a socio-cultural duty and a labor of love, rather than a positive contribution equivalent to a wage. 
By the Victorian era, the idea of the "Angel in the house" as poet Coventry Patmore described the role of the ideal wife, was firmly embedded as a cultural conceit. This mythic traditional marriage conceit flourished along with other Victorian ideas about women as the weaker sex, pure by nature and not as overtly sexual as men, with a higher moral sensibility. The extended family of the middle ages was deprecated in favor of every man as lord and master of his own home. That started to change with World War II.
During the second World War, a great many women were employed in jobs related to the war effort, jobs that had previously been seen as "men's work." Many women found that they liked working for a wage, and that they liked their jobs. With the advent of washing machines, electricity and modern refrigeration, there was less time-consuming physical labor associated with keeping house. Nonetheless, when the troops returned, there was tremendous social pressure to replace women employees with men. There was economic pressure as well; the tax code was changed in 1948 to favor households with a single wage earner, a provision referred to as the "marriage tax" or marriage penalty since two-earner households with a married couple filing jointly often pay more tax than they would filing separately. 
It's About the Sex
Another ahistoric assertion about the history of marriage in the context of the challenge to same-sex marriage is that marriage is about reproducing sexually via coitus. Even the strictest definitions in Canon law would not accept this as a definition of marriage. As Peter Lombard, the Bishop of Paris, noted in the middle of the twelfth century, if coitus were necessary to establish a marriage Mary and Joseph would not be perceived as married when Christ was born. 
If marriage is about sexual reproduction, are heterosexual couples who do not engage in coitus no longer married? Many heterosexul couples can't conceive via coitus; are they no longer married? What about couples who adopt; do adopted children "count?" What does the association of children as inherent in marriage mean for couples or singles who have children outside of marriage? What does it mean for their children? What does that mean for the states that allow singles or same-sex couples to adopt children? What does that mean for their children?
By the middle of the twentieth century in the U. S., children born out of wedlock were able to inherit on equal terms with those born within wedlock. At the same time as illegitimacy was increasingly not considered of interest to the state, increasingly effective birth and conception control meant that women could choose to be active sexually without being married, or married without having children.
In 1965, Griswold v. Connecticut, a case in which the Executive Director of Planned Parenthood of Connecticut, and a licensed MD were previously convicted of giving a married couple information and prescribing a contraceptive for the wife's use was overturned when Justice Douglas struck Connecticut's ban on birth control as violating the privacy of the marital bedroom and a violation of "fundamental" rights of privacy, marital choice, and family creation implied in the Constitution.
Seven years later in 1972 the Supreme court struck down a Massachusetts law that forbade the sale or prescription of birth control to unmarried people. SCOTUS ruled that under the principle of equal protection under the law, Massachusetts could not prohibit contraception to unmarried adults while permitting it for married adults. Eisenstadt v. Baird effectively tied the right to bear or beget a child to the individual, rather than the couple.
If Federal law sees preventing conception as a private matter for individuals, then that applies to choosing to conceive children as much as choosing not to. Choosing to conceive a child out of wedlock, choosing to adopt, choosing to conceive via artificial insemination; these are all matters of individual decision, independent of sexual orientation. Women in heterosexual relationships and women in same-sex relationships may rely on artificial insemination, or on conceiving in vitro or via coitus. If women and men in heterosexual relationships may conceive and parent children via methods other than coitus, equal protection under the law suggests that women and men in same-sex relationships and their children deserve the same rights.
The emphasis on coitus as a privileged sex act is telling; this objection to same-sex marriage it isn't really about children, it's about sex. It is at least partially based on ignorance regarding human sexuality. It's not as if heterosexual people don't engage in the same wide array of sexual behaviors that people in same-sex relationships engage in. Are heterosexual couples who engage in anything but penis-in-vagina sex consequently not married?
I suspect that part of the obsession about coitus and reproduction is a desire to prohibit what many think of as "transgressive sex," vaguely wrapped up under the heading of sodomy. In various SCOTUS decisions related to homosexuality the court is surprisingly vague about the specific sex act being referred to as sodomy. The American Heritage Dictionary defines sodomy as "Any of various forms of sexual acts regarded as perverted, especially anal intercourse, oral-anal contact, or sexual intercourse with an animal," that is, anal sex, cunnilingus, fellatio and bestiality. 
If heterosexual couples can engage in sexual behaviors other than coitus, it is unreasonable to deny that right to same-sex couples; this was essentially the majority decision in Lawrence v. Texas when the Supreme ruled in a six-to-three decision in 2003 that anti-sodomy laws were unconstitutional.  In the opinion delivered by Justice Kennedy, the Justice observed that "When sexuality finds overt expression in intimate conduct with another person, the conduct can be but one element in a personal bond that is more enduring" (p. 567). Justice Sandra Day O'Connor filed a concurring opinion in which she argued that because the Texas law prohibited homosexual sodomy and not heterosexual sodomy, it was a violation of the Equal Protection Clause of the Fourteenth Amendment. The Court's decision in Lawrence v. Texas notes that "It was not until the 1970's that any State singled out same-sex relations for criminal prosecution, and only nine States have done so" (570).
The final objection to same-sex marriage is the assertion that, roughly, religious freedom means that we can't allow same-sex marriages because some members of some religions oppose it. This is a bit silly, historically as well as contemporaneously. We have no state religion in the U. S. The Constitution guarantees religious freedom. No one is going to force any clergy to officiate at same-sex weddings. No one is going to force any church or temple to allow a same-sex wedding to be held in their edifice. Churches and clergy refuse to marry couples on a regular basis for all sorts of reasons, including religious reasons, concern about the couple's compatibility, or even personal dislike.
As it stands now in all 50 states and the District of Columbia, marriage depends on a license issued by the state. The state determines who may be married and who may witness, and the state authorizes various people to officiate and sign the marriage license as the presiding official. It's a state license; not a religious license, which means that all marriages are secular at heart. The difference between a same-sex marriage and a heterosexual marriage is that DOMA denied the Federal protections (as well as the responsibilities) to same-sex couples that heterosexual couples enjoy, even if same-sex couples are legally married in one of the states or countries that allow same-sex marriage. Post the overturn of DOMA, the status of individual same-sex marriages depends on where they were married and where they live and where they work.
For my part, I don't think any church or state can authenticate or create a marriage for any couple; the couple do that themselves in the ways they care for each other and build their lives. I don't need the state's blessing on my marriage; what I need is the reassurance that should I be hospitalized again, my partner can make important decisions about my care when I can't speak for myself. Despite some small protections in Federal law, some states and hospitals still tend to do what they want.
I want to know that when we buy a house together, should I die (as the older of us, that's likely) first, she won't be saddled with thousands in estate tax on a property we have purchased and cared for together. I'd be delighted to pay the marriage tax penalty, instead of the thousands of dollars in legal fees for documents that don't work in every state that we're stuck with now. I'd be especially happy if we could both contribute to various Federal investment programs as a couple, instead of individually, based on who has what sort of benefit at work.
Most of all though, I want the same kind of recognition that we are a couple that other couples have; I want a spouse. As Justice Ruth Bader Ginsburg observed to Paul Clement, the lawyer arguing for the preservation of DOMA before the Supreme Court, "if we are totally for the States' decision that there is a marriage between two people, for the federal government then to come in to say no joint return, no marital deduction, no Social Security benefits; your spouse is very sick but you can't get leave; people— . . . one might well ask, What kind of marriage is this?" As Ginsburg subsequently noted "There are two kinds of marriage," under DOMA, there are "Full marriage and the skim-milk marriage."  Despite the recent decision by SCOTUS, because of state statutes there are still two (or more) varieties of marriage depending on where you were married, where you live, and where you work.
I'm not willing to settle; I'm especially not willing to settle for skim milk based on inaccurate assumptions about history. History doesn't have a unanimous takes on what marriage is or who may be married; we can decide that for ourselves as a nation.
Illustration courtesy of shutterstock.
 On Tuesday, March 26, 2013 SCOTUS heard arguments in Dennis Hollingsworth, et al. v. Kristin M. Perry, et al, the case to overturn California's Proposition 8 and on Wednesday, March 27, 2013 they heard arguments in United States v. Edith Schlain Windsor, the case to overturn the Federal Defense Of Marriage Act (DOMA). Both cases were decided on June 26, 2013.Back
 For the first fifteen hundred years or so the church made much of Luke 20: 35 "But they which shall be accounted worthy to obtain that world, and the resurrection from the dead, neither marry, nor are given in marriage."Back
 Polygyny (one man with multiple wives) is not at all unknown in the U. S. history. There were the so-called "free lovers" of the 1850s, followed shortly after by the Oneida community in upstate New York. Polygyny became an issue for the statehood of Utah after the Church of the Latter Day Saints founder Joseph Smith's 1843 vision regarding "plural marriage" as a basic principle of the church. The Supreme Court determined in Reynolds v. U.S. "as a law of the organization of society under the exclusive dominion of the United States, it is provided that plural marriages shall not be allowed. Can a man excuse his practices to the contrary because of his religious belief? The permit this would be to make the professed doctrines of religious belief superior to the law of the land, and in effect to permit every citizen to become a law unto himself.") that polygamy was not protected by the first amendment. In 1881 Congress passed the Edmunds act criminalizing bigamous "unlawful cohabitation" and requiring men and women to swear that they were not polygamist/wed to a polygamist before being able to vote. In 1887, Congress passed the Edmunds-Tucker act which made it possible to seize church property, assigned jurisdiction over the crimes of adultery and incest to the Federal court in Utah In 1890 a Latter Day Saints Church "Manifesto" reversed the church's stance regarding polygyny publicly. Polygamy is still not legal in the United States. Cott, Nancy F. Public Vows: A History of Marriage and the Nation. Harvard University Press: Cambridge, Massachusetts, 2000. 117–120. Subsequently identified as Cott. Elsewhere in the world, polygyny is at least culturally accepted, and under Sharia law, legal (Surah 4 verse 3 of the Quaran). Back
 There doesn't appear to even be a Christian marriage ceremony or ritual before the 4th century. See Philip Lyndon Reynolds. Marriage in the Western Church: The Christianization of Marriage during the Patristic and Early Medieval Periods. Boston: Brill Academic, 2001. 62. Historian John Boswell presents convincing arguments for same-sex weddings and marriages conducted in Orthodox and Roman Catholic churches in the early Middle Ages; see John Boswell. Same-Sex Unions in Premodern Europe. especially pp. 162–261.Back
 Gratian's requirement that marriage requires mutual consent is still part of standard marriage ceremonies secular or sacred in the form of a question asked of the would-be spouses "do you . . . "Back
 In 1215 the Church established canon law about the conditions of marriage at the Fourth Lateran Council (see especially Canons 50–52). The Council also established clearer rules regarding consanguinity, affinity (marrying in-laws, or step children) and incest, and required banns announcing the betrothal before the marriage. A marriage was valid only if both participants consented and consummated their relationship sexually. Marriage didn't require a priest or a church and it wasn't a sacrament. Back
 It was another four hundred years or so before the church formally declared that weddings must be performed in public, by a priest, and before witnesses. Back
 Various states prohibited marriages between "white" and Native American including Inuit, various definitions of Asian (some states referred to Mongolians) as well as African Americans, and East Asians, including Indians. Back
 See also "The Science on Same-Sex Marriage. Back
 Coontz, Stephanie. Marriage, a History: How Love Conquered Marriage. Penguin Books (February, 2006). 115, 186. Subsequently identified as Coontz. Coverture is the equivalent of the Roman concept of cum manu, in which a woman was "under the hand" of a man whether a father, brother or spouse. The 1887 Edmonds-Tucker act designed to curtail the Church of Latter Day Saints' plural marriages denied the principle of coverture to plural wives or polygamous husbands, which meant that wives could testify against their husbands (Cott 120). Back
 Coontz 186. England overturned the principle of coverture via the Married Women's Property Act of 1870 and 1882 in which women with any property of any sort had to give up all rights to it to their husbands on marriage. Back
 Historian Stephanie Coontz associates this late eighteenth and early nineteenth century change in marriage roles with the creation of the "marriage myth" of a protective male breadwinner and a stay-at-home female spouse (Coontz 154 ff). Back
 Cott 191–94. There's a certain irony that DOMA, by denying same-sex marriages Federal status may be costing both the nation and the couples in question, a lot. Back
 Lombard states this in his fourth book of Sentences or distinctions regarding the sacraments. Finn, Thomas. "The Sacramental World In The Sentences Of Peter Lombard." Theological Studies 69 (2008): 557–582. 575. Back
 The meaning of sodomy at various times has been whatever current custom considered "unnatural," whether it was oral sex, any position other than the "missionary" for coitus or masturbation, alone or with a partner. As the Lawrence v. Texas amicus brief from historians George Chauncey, Nancy F. Cott, John D'Emilio, Estelle B. Freedman, Thomas C. Holt, John Howard, Lynn Hunt, Mark D. Jordan, Elizabeth Lapovsky Kennedy, and Linda P. Kerber notes "sodomy prohibitions have varied enormously in the last millennium (and even since our own colonial era) in their definition of the offense and in their rationalization of its prohibition . . . Prohibitions against sodomy are rooted in the teachings of Western Christianity, but those teachings have always been strikingly inconsistent in their definition of the acts encompassed by the term." Back
 The decision in Lawrence v. Texas overturned the earlier 1986 decision in Bowers v. Hardwick. Dale Carpenter in Flagrant Conduct: The Story of Lawrence v. Texas. W. W. Norton: New York, 2012 covers the history of Lawrence v. Texas, including the conflicting testimony of the witnesses. Back