the marriage ceremony is most likely neolithic, but marriage as way of life is probably not neolithic. there are many examples in the animal world of strictly monogamous relationships and human case could be just like that. in any case there is no evidence for and against, so please indicate this is your personal opinion and not some kind of universal fact.
i agree. personally, i want security of my own life and my child's life. so, if i build a raw paleo community, i do want some family structure in that community where there will be married couple and they take care of their children sincerely. if i don't do that, than what's the difference between me and hippies?