Quoting the bible only proves my point. Marriage was set up by religion. You have not shown that anything in Genesis 2 is historical. Second, by making a distinction between polygamy and open marriage you are saying that it is perfectly fine for a man to cheat on his wife by marrying another wife. Would this be the same God being worshiped that established one man and one woman from Genesis 2? If open marriage is a sin then why did the God of Genesis 2 decide that polygamy is not a sin? Is it possible that your God is a misogynist? Then later did that same God decide he made a mistake and change his mind by the time the New Testament came along?
So your choices are there is more than one god represented in the bible. In which case, which god said what? Or the bible's God can't make up his mind. In which case, is your no longer perfect? Or is the bible just the creation of several Mideastern men and thus just the work of a religion?
Not looking to debate you on this, (especially in a thread about a man that I wish to expose as the lying and cheating jerk that he is) but if you were honest at all, you can see how flawed your position is by using the bible. Marriage is a construct of religion and is not unique to modern Jewish and Christian faiths. Now if you would like to argue that ALL religions are equally inspired by God, then feel free to make that case.