We are all born atheists, religion is what someone gives to us.
You have prairie dogs that have evolved to be monogamous, others are not, their brains are wired differently, one the ocytocin receptors work differently. One is not reading the bible and the other isn't. In the case of one monogamy is part of their evolution and social structure. The other it has no baring.
What I am getting at is who is to say the marriage is necessary for humans? Or even moral??? It is so deeply engrained in us its hard to imagine it otherwise, but that is not because of GOD its because of indoctrination. I am not preaching against marriage, but honestly I believe it is as man made as the bible itself. If two people want to be together forever and not with anyone else and can do it, more power to them. It they chose a different path I don't believe they deserve eternal destruction by god.
The bible didn't even start as the "Holy Bible" it was a library of jewish writings and there was a lot more to it than just the Holy Bible you thump today. It's existence is a result of a need for a foundation myth and political social control reasons. That is as plain as day if you read it in the context of history with its lack of actual archeological backing.