Who first invented marriage?

Someone in pre-history.
It certainly wasn't the christian church.

Pagans first invented marriage.

It goes way back into the pagan past of our pre-history and has nothing tp do with any particular god.

It's a government invention, marriage is pretty much an official registered relationship recognised by the government.

Hunter gatherer societies to remove the cause of territorial squabbles with neighbours. As religions developed, they seemed to think it was their idea but it never was.

I think its origin precedes history.

God said that it is not good for man to be alone, so He created a woman, and declared that a man shall leave his father and mother and cleave to his own wife. Marriage was created (not invented) by God, FROM THE BEGINNING of mankind on earth.

It wasn't a Christian thing, it wasn't a muslim thing, it wasn't even a Jewish thing.

It is probably as old as civilization. We see a description of the betrothal in the story of Isaac and Rebeccah, so it obviously is a very elaborate set of traditions by that time.

My guess is that in early stone age times, they needed a way of telling everyone not to try to have sex with just any girl. They needed a way of saying that certain women were off limits. This isn't what you think. It was a matter of experience. Men fighting over a woman got hurt and got killed. Thus, a good hunter lost some or all of his hunting skill, and everyone starved.

This is God's concept. Formal serious business.

God
Adam and Eve
not Adam and Steve

God of the bible....

GOD DID! As the Bible teaches us!