There is no debate. If someone were to point out a written record of an actual marriage that is using equivalent rites to a heterosexual marriage with exact legal recognition of that contract plus additionally rights over children, I will relent. This is not some ideological position. It's simply an absence of any such thing. For example, it should not be controversial to say that surrogacy is a modern day thing and that there is no historic record prior to it of a woman being considered the biological mother of a child she didn't bear. People are having their feelings about gay marriage override simple historical fact.

The Wikipedia page on the history of gay marriage makes the exact same point I've made. My statement is not controversial and is the accepted view. There are countless examples of gay people considering themselves married, but without societal recognition equivalent to heterosexual marriage. You cannot consider this the same as gay marriage because gay rights activists said that similar arrangements in the modern day were not enough and they needed to be married in an equivalent fashion: https://en.wikipedia.org/wiki/History_of_same-sex_unions