“Virginia Attorney General abandons natural marriage,” reads a Liberty Counsel press release. “Marriage was not created by religion or government and is ontologically a union of one man and one woman.”

Really? What is so natural about exclusively one-man-one-woman marriage, as opposed to polygamy, or, more precisely, social acceptance of either monogamy or polygamy?

Polygamy has been common throughout human history, present in a vast range of cultures — according to the Ethnographic Atlas count, many more than practiced solely monogamy (though of course with such counts much depends on how you separate or group together cultures). The Old Testament of course reports this as to the ancient Jews, and on this point I suspect it is historically accurate. Many American Indian tribes have practiced polygamy. The Muslim world of course still allows polygamy, and my sense is that this reflects continuous practice in many areas from the pre-Muslim era.

To be sure, nature also provides roughly equal numbers of male and female babies, and historically nature has made it hard for men to support more than one wife. Still, very many societies throughout human history have allowed polygamy for those men who had the wealth or social status to attract multiple women at once.

I’m certainly open to arguments that certain behavior patterns are “natural” for humans. It’s natural, I strongly suspect, to love your children. It’s probably natural to exhibit at least certain forms of sexual jealousy. It may well be natural to practice either monogamous or polygynous — one-man, many-women marriage — and not polyandrous marriage (one woman, many men) or many-woman many-man marriages; there certainly are very few societies that have exhibited that. It seems likely that it’s natural for some people to prefer homosexuality (not to say that homosexuality or heterosexuality is completely genetically determined), just as it’s natural for some people to be born left-handed or redheaded, though for obvious reasons it’s not natural for this to be the norm in a society.

Just as certain mating behavior patterns in animals must be natural, so certain behavior patterns in humans must be natural, though of course there is more opportunity for more arbitrarily chosen overlays on top of that in humans. But I see no evidence, given the long and broad history of polygamy, that “natural marriage” is solely or even overwhelmingly “a union of one man and one woman,” whether ontologically, biologically, or any other way.

This having been said, one can certainly argue that a union of one man and one woman is better for society or for the parties involved (or for that matter that it is more God’s will, if you believe in God), and should therefore be preferentially treated by the law. One can likewise argue, as I have, that one-one pairings, whether opposite-sex or same-sex are better for society than polygamous relationships, so that same-sex two-person marriage should be recognized but polygamous marriages should not be. But the important point is that choosing what sorts of relationships to legally recognize as “marriage” is a matter of social choice, not a “natural” or “ontological” matter.

(I set aside in this post the possibility that everything humans do should be treated as definitionally natural, on the theory that anything that humans do stems indirectly from our nature; if you accept that possibility, then it becomes even less sensible to call monogamy and only monogamy “natural marriage.”)