Clearly, none of the justices or the lawyers thought to ask an anthropologist. Any knowledgeable anthropologist would easily have answered "yes."
Let me cite a few well-known cases (well-known to anthropologists, at least).
The Nuer of South Sudan permitted women to marry other women. Among the Nuer, marriage involved the payment of cattle as bride wealth from the husband's kin to the wife's, a payment that gave the husband paternal rights and allowed him to bequeath his livestock to his sons.
While it was relatively unusual, some women acquired substantial property and would marry other women to bear them heirs. The biological father of any such children was irrelevant.
The woman who married their mother was recognized as their legitimate father. Such woman-to-woman marriages were by no means unique to the Nuer. For example, the Igbo of Nigeria, thousands of miles away, had similar kinds of marriages.
Closer to home, there was a class of persons among the Navaho known as nadleehi, biologically male but who dressed in women's clothes and performed women's occupations. They were by no means outcasts or even socially marginal.
An important Navaho myth tells of a quarrel between First Man and First Woman, leading to the disastrous separation of the sexes and ultimately to the birth of monsters. Only the nadleehi, able to travel between the men and the women, could restore the world to normalcy. Men could marry nadleehi, who were reputed to make excellent wives. Other Native American cultures had very similar institutions.
Of course, I suspect that Scalia would object that these examples don't necessarily matter to us. After all, many cultures accept polygyny, the marriage of one man to several women, or more rarely, polyandry, the marriage of one woman to several men. This hardly means that such marriages should be legal in the United States.
But marriage between a man and more than one woman was certainly permissible in the Old Testament. Indeed, the Bible sanctioned even more exotic forms of marriage, such as the levirate.
If a married man died without a son, his brother or, if necessary, a cousin was obliged to take his wife, support her and beget an heir in his name. (This is spelled out in Genesis, chapter 38, not to mention the entire Book of Ruth.) Jacob, the ancestor of the twelve tribes of Israel, was simultaneously married to two sisters who were his first cousins on his mother's side and only slightly more distantly related on his father's side.
I am not suggesting that we should accept Biblical precedent, that if it was good enough for Jacob, it's good enough for us. But I do want to call into question Justice Anthony Kennedy's assertion that the same definition of marriage "has been with us for millennia." Even within our own religious tradition -- at least for those of us who are Jewish, Christian or Muslim -- the concept of marriage has changed radically over millennia.
The notion that a single paradigm of marriage is a human universal, or even historically constant within our own tradition, is easily refuted.
Does this mean that anything goes? Of course not.
We anthropologists have often been unfairly accused of slap-happy relativism, even though I can assure you that most of my colleagues are sensible and decent people. My point is simply that the meaning of marriage has always been culturally and historically variable, and consequently, that the legal definition should represent social consensus.
If same-sex marriage is religiously objectionable to a minority of the population, so be it. So is eating meat, but I do not think it would be right for the Supreme Court to impose vegetarianism on the American people on religious grounds.