The counsel arguing in support of Proposition 8 asserted that there is a public policy interest in defining marriage as between a man and a woman. That interest? procreation, he said:

the State's interest and society's interest in what we have framed as responsible procreation is vital

Justice Kagan (with an assist from Justice Breyer) pursued this in a sequence of exchanges that should resonate with every married person who has no children, has no intention to have children, cannot have children, adopted children, or imagines someday fostering or adopting children:

JUSTICE KAGAN: Mr. Cooper, could I just understand your argument. In reading the briefs, it seems as though your principal argument is that same- and opposite -- opposite-sex couples are not similarly situated because opposite-sex couples can procreate, same-sex couples cannot, and the State's principal interest in marriage is in regulating procreation. Is that basically correct? ... JUSTICE BREYER: ... What precisely is the way in which allowing gay couples to marry would interfere with the vision of marriage as procreation of children that allowing sterile couples of different sexes to marry would not?... Am I not clear? Look, you said that the problem is marriage; married who can't have children. To take a State that does allow and say -- there, what is the justification for saying no gay marriage? Certainly not that it is an institution that furthers procreation.... Now, what happens to your argument about the institution of marriage as a tool towards procreation? Given the fact that, in California, too, couples that aren't gay but can't have children get married all the time. MR. COOPER: Yes, Your Honor. The concern is that redefining marriage as a genderless institution will sever its abiding connection to its historic traditional procreative purposes, and it will refocus, refocus the purpose of marriage and the definition of marriage away from the raising of children and to the emotional needs and desires of adults, of adult couples.

At this point Justice Kagan takes over again, and pushes the pro-Prop 8 counsel to an extraordinary and biologically just plain weird point:

JUSTICE KAGAN: Well, suppose a State said, Mr. Cooper, suppose a State said that, Because we think that the focus of marriage really should be on procreation, we are not going to give marriage licenses anymore to any couple where both people are over the age of 55. Would that be constitutional?... Because that's the same State interest, I would think, you know. If you are over the age of 55, you don't help us serve the Government's interest in regulating procreation through marriage. So why is that different? MR. COOPER: Your Honor, even with respect to couples over the age of 55 it is very rare that both couples -- both parties to the couple are infertile, and the traditional -& ; ( .) JUSTICE KAGAN: No, really, because if the couple -- I can just assure you, if both the woman and the man are over the age of 55, there are not a lot of children coming out of that marriage. MR. COOPER: Your Honor, society's -­ society's interest in responsible procreation isn't just with respect to the procreative capacities of the couple itself. The marital norm, which imposes the obligations of fidelity and monogamy, Your Honor, advances the interests in responsible procreation ... It's designed, Your Honor, to make it less likely that either party to that -- to that marriage will engage in irresponsible procreative conduct outside of that marriage. Outside of that marriage. That's the marital -- that's the marital norm. Society has an interest in seeing a -year-old couple that is -- just as it has an interest of seeing any heterosexual couple that intends to engage in a prolonged period of cohabitation to reserve that until they have made a marital commitment, a marital commitment. So that, should that union produce any offspring, it would be more likely that that child or children will be raised by the mother and father who brought them into the world.

You can listen to the entire thing if you like. Or read it.

In a country where today, 48% of children are born to mothers who are not legally married, this simply seems remarkably out of step with reality.

For me the amazing thing, as ever, is the recourse to false claims that marriage has a singular, stable, history: "its abiding connection to its historic traditional procreative purposes". Back in 2012, I considered at some length the historical evidence against defining a deep history for the one man-one woman marriage form as original, universal, or in any meaningful sense "abiding". As I wrote then

"Marriage" in the U.S. today is a civil contractual relationship. That civil contractual relationship has evolved over the history of this country, from inscribing inequality between partners to a contract between equals. Even in the brief history of this country, then, marriage has not been consistently defined and has been constantly evolving...

The counsel arguing the case to uphold Proposition 8-- which would deny equal access to marriage to couples who are the same biological sex-- used the term "the age-old definition of marriage" when the justices finally let him begin his argument for the merits of the case.

"The age-old definition of marriage".

To an anthropologist, that sounds remarkably quaint. Whose age-old definition? Globally, the cultural tradition being argued is one among many, and as the American Anthropological Association said in 2004 in a statement inspired by a call for a constitutional amendment to enshrine that definition,

The results of more than a century of anthropological research on households, kinship relationships, and families, across cultures and through time, provide no support whatsoever for the view that either civilization or viable social orders depend upon marriage as an exclusively heterosexual institution. Rather, anthropological research supports the conclusion that a vast array of family types, including families built upon same-sex partnerships, can contribute to stable and humane societies.

That's right. Stable societies have been based on many different kinds of social relations that provide for the birth, care, and of children, as well as the many other activities that marriage covers in modern US society: joint property ownership, joint medical and end of life care, joint taxation, none of which-- contrary to the somewhat bizarre, reductive view of marriage argued before the Supreme Court-- are about "procreation".

The counsel for the Prop 8 supporters got himself in trouble-- from an anthropological perspective-- every time he made a statement about inherent characteristics of marriage. He should have asked an anthropologist.

As cultural anthropologist Robert Myers wrote in 2004,

Although marriage's form, duration and meaning vary from time to time and culture to culture, most Americans frown on anything other than familiar monogamy.

Myers goes on to describe some other aspects of marriage that don't fit the definition of marriage that the counsel in the current Supreme Court case advanced:

Most Americans find marriage to a first cousin repulsive, although a strong preference for a marriage partner who is your first cousin on your father's side is the rule in dozens of traditional societies. In France, it's even possible to marry your deceased fiancé.

But wait, there's more; Myers notes that the 'traditional' concepts of marriage in the US

monogamy between a man and a woman, and reject societies that allow polygamy or , the marriage of one woman to several males, often brothers. But we will allow marriage to any number of partners, as long as it is to only one at a time.

If you are getting the impression that anthropologists have a lot to say about marriage: well, yes. Kinship is, after all, one of our historic, signature issues. And that gives us something to say about the core claim by counsel for Prop 8. As John Borneman and Laurie Kain Hart wrote in the Washington Post in 2004,

Marriage generally functioned to provide a "legitimate" to children -- a kind of "last name." Yet, the structure of these arrangements was extraordinarily diverse: Biological paternity was not universally the basis of identity -- as, indeed, it is not in the case of adoption in America. In many cases, the biological father (the Latin term is genitor) was distinct from the legal father (pater) produced by the marriage contract and ceremony. Alternatively, it could be the mother's family and not the father that bestowed identity on a child.... But marriage has not been solely about children. In most societies known to us, everyone marries; it is an expected rite of passage and part of the normal life course of all adults.

Their conclusion is as relevant today as it was then:

Marriage is, then, foundational because it provides a recognized form of identity and security for children in society. Its function is not universally to produce children but to provide legitimate forms for their care. And marriage's primary accomplishment is not to regulate sex (as a quick glance at American society would tell us). The institution survives despite , and sex does not by itself create marriage.... What, then, about restriction of the legal bond of marriage to a man and a woman? Does marriage have to be heterosexual? The human record tells us otherwise. While the model of marriage is arguably heterosexual, the practice of marriage is not. In a broad spectrum of societies in Africa, for example, when a woman's husband dies, she may take on his legal role in the family, and acquire a legal "wife" to help manage the domestic establishment. This role of wife is above all social, and not contingent on her sexual relations. These societies, which practice heterosexuality, take this woman-woman marriage as commonsensical; they recognize that above all marriage functions socially to extend and stabilize the network of care. As for marriage as a legal institution, the ethnographic record makes clear that law expresses the dominant of the group. Our history reflects the evolution of our values, and we as Americans are most proud of our deepening tradition of civil rights. To deny marriage to same-sex couples... expresses a rejection of this civil rights tradition and a to a of exclusion.

If you are going to make a claim about universal human relations-- ask an anthropologist.