We have all seen the bumper stickers insisting that marriage "is between one man and one woman," but throughout most of human history, that hasn't really been the case. Anthropologists say 83 percent of societies they have studied traditionally permitted polygyny — marriage with multiple wives. (The more common term "polygamy" has the broader definition of having multiple spouses.) Just 17 percent insisted on monogamous marriage. So how did social monogamy, which has spread in the past few centuries thanks to the influence of Euro-American culture, come to be? Most evolutionary ... Read More