The Banning of Polygamy?

My theory is that, with the embrace of Christianity by pagan Rome, what developed was a actually more of a hybrid religion (we can also see this at work in the catholic church even today, where converts from various cultures retain certain aspects of their pagan customs , rituals etc.). So what we ended up with was more of a Romanized Christianity, rather than a Hebrew Christianity...I hope that makes sense, and I think Augustine's statements below bears this out rather well.

Augustine :

"Saint Augustine saw a conflict with Old Testament polygamy, and wrote about it in *The Good of Marriage* (chapter 15, paragraph 17), where he stated that though it "was lawful among the ancient fathers: whether it be lawful now also, I would not hastily pronounce. For there is not now necessity of begetting children, as there then was, when, even when wives bear children,
it was allowed, in order to a more numerous posterity, to marry other wives in addition, which now is certainly not lawful." He declined to judge the patriarchs, but did not deduce from their practice the ongoing acceptability of polygamy. In another place, he wrote, "Now indeed in our time, and in keeping with Roman custom, it is no longer allowed to take another wife,
so as to have more than one wife living."