There’s a fascinating anthropological study in support of gay marriage in today’s Washington Post. Here’s the key graf:
Our society no longer approves of treating women as incompetent minors and the wards of their husbands within the structure of a patriarchal union. We do not approve, generally, of plural marriages — the basis of our disapproval being that they abrogate the rights of women and especially of young girls. We no longer generally feel that the sole function of women in society is to produce children and serve men as domestic labor. In other words, when we censure certain types of marriage, the basis on which we do so is our defense of individual human rights. This is our ethical standard.
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 infidelity, and sex does not by itself create marriage.
I suggest you read the whole thing.