The conservative case against gay marriage is often based in large part on the idea that there is and has always been only a single valid form of marriage: that between a single man and a single woman who live together and raise children together. Guess what? The conservative opponents of gay marriage are wrong. Indeed, they couldn't be more wrong - which suggests that they either never bothered to research the topic before coming to their conclusions or they did and are deliberately trying to deceive people.

John Borneman and Laurie Kain Hart write in the Washington Post:

In the 1860s New York lawyer and anthropologist Louis Henry Morgan attempted a systematic cross-cultural study of the institution of marriage. Morgan's data were imperfect, but he was able to demonstrate that the record of human societies showed a startling diversity of socially approved forms of marriage. All societies had some form of regularized partnership, but no single standard human form could be identified. Generally, even within a society, there was a certain elasticity of marriage forms.

Marriage generally functioned to provide a "legitimate" identity 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. Only in post-classical Western societies do we find high numbers of unmarried people. Unlike other peoples, we consider marriage -- however desirable or undesirable -- optional. ... 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.

Borneman and Hart argue that everywhere marriage occurs, it conforms to certain ethical standards that apply widely in that society. What are the ethical standards for marriage in America? We can understand them better by looking at what sorts of marriages might be legally valid but are considered "wrong" by most people. A marriage which is contracted simply so that the husband can have an unpaid domestic servant, for example, would be wrong even if legally valid. Why? Because it undermine's the spouse's individual human rights.

That, then, is the basic standard for marriages in America. Marriage laws which enhance and defend individual rights (like the right of women to leave an abusive marriage) and proper; those which undermine people's rights (like denying gay couples the ability to marry) are improper. Where a person stands on this says not so much about how they view marriage but how they view civil rights.

Read More:

• Ethics of Gay Marriage
• Separation of Church and State 101
• Religious Right
• Evangelical Christianity & Homosexuality