Marriage has definitely existed in (almost) every culture.
But the definition and form of marriage has varied quite dramatically, along with its social and legal implications and consequences.
What has never existed before, AFAIK, is anything resembling true “gay marriage,” but the variety of marriages between men and women is quite large.
I’m afraid you’re disputing something I didn’t say. I never claimed that there wasn’t variety. In fact, I implied that there was.