They were practicing marriage in Mesopotamia and Babylon as a legal contract to “exchange goods” aka a woman between a suitor and a woman’s father. Divorce was only allowed by law in certain circumstances like if a woman could not bear children. It has no roots in any modern religion, though it was later adopted into a practice in ancient Judaism which was adopted into Christianity.

If you want to bring modern religion into it though, the Middle Ages was when the Catholic Church turned that contract between a woman’s father and a suitor into a sacrament via Canon Law. Canon Law states:

Can. 1057 “The consent of the parties, LEGITIMATELY MANIFESTED BETWEEN PERSONS QUALIFIED BY LAW, makes marriage; no human power is able to supply this consent. Matrimonial consent is an act of the will by which a man and a woman mutually give and accept each other through an irrevocable covenant in order to establish marriage.”

Can. 1058 “All persons who are not prohibited by LAW can contract marriage.”

Can. 1059 “Even if only one party is Catholic, the marriage of Catholics is GOVERNED NOT ONLY BY DIVINE LAW BUT ALSO BY CANON LAW, without prejudice to the competence of civil authority concerning the merely civil effects of the same marriage.”

Can. 1060 “MARRIAGE POSSESSES THE FAVOR OF LAW; therefore, in a case of doubt, the validity of a marriage must be upheld until the contrary is proven.”

Marriage has always been a contract officiated by laws and contracts point blank. The idea that they have been two separate things until the US government stepped in is historically incorrect and only seems to pop up when someone arguing “religious freedom” against same sex marriage is told we could give two shits less about your religion and that we care about the law. I really think you have misinterpreted what history and religion have said.