I don't usually post to these threads but this statement caught my eye.
Do you really believe that pre-Christian (or pre-Abrahamic) societies had no such thing as marriage?
I myself was married in a civil ceremony. Does this not count in your eyes?
A lot of our civil laws are taken from the laws of the Bible.
I am pretty sure that prior to these times it was natural for a man to take 1 wife and cling to her, support her and protect and care for their offspring together, it's just that in the Bible God blessed this practice and made it a covenant just like the covenant between God and Abraham.