A colleague of mine came by my office today to ask about the Jewish position on monogramy. I told him that there is/was a dramatic difference between Sephardi and Ashkenazic Jewry, that monogamy was decreed sometime in the 11th century (I believe) by (I believe) an Eastern European rabbi, whereas polygamy remained into the 20th century in a number of Sephardi communities. Indeed, I had a friend in Israel who had two mothers-in-law, because his (now former) wife had emigrated from Yemen, and her father had two wives. I'm quite certain that Israel requires monogamy among Jews--I have no idea what the situation is with regard to Israeli Moslems--but polygamy was "grandfathered," as it were, for Jewish immigrants who were involved in plural marriages.
I hypothesized to my colleague that an obvious explanation for the difference between the two communities is that Jews in Europe felt pressures to conform to the mores of the dominant Christian community, which was monogamous, whereas there was obviously no such pressure in Moslem-dominated Sephardi areas. Similarly, I have little doubt that the Church of LDS would have maintained polygamy had the surrounding culture been more tolerant.
sandy