Just ask yourselves, historians, when was monogamy introduced on to the face of the earth? When those buccaneers, who settled on the peninsula where Rome now stands, could not steal women enough to have two or three apiece, they passed a law that a man should have but one woman. And this started monogamy and the downfall of the plurality system. In the days of Jesus, Rome, having dominion over Jerusalem, they carried out the doctrine more or less. This was the rise, start and foundation of the doctrine of monogamy; and never till then was there a law passed, that we have any knowledge of, that a man should have but one wife.
[Source: Journal of Discourses 12:262; WikiQuotes: Brigham Young, http://en.wikiquote.org/wiki/Brigham_Young]