“Just as societies have advanced [and] then faded away into a state of general decrepitude, so in each of them has marriage first previously changed from a temporary affair based on mutual consent to a lifelong association of one man with one woman, and then turned back to a loose union or to polygamy. … The whole of human history does not contain a single instance of a group becoming civilized unless it has been absolutely monogamous, nor is there any example of a group retaining its culture after it has adopted less rigorous customs.”
~Oxford sociologist J.D. Unwin