A study of those who engaged in polygamy in the Old Testament reveals that they all paid dearly in fractured families. It is illogical to assume that since the Bible records people behaving in a particular way or manner that God is recommending it. As mentioned above, God gave the first man only one wife. A great opportunity, if he wanted us all to have multiple partners, to teach us this lesson. But he did not.
Birth records throughout time demonstrate that births of males and females are about equal.
As stated above, the picture of the relationship between Christ and the church is monogamy. Many examples in the Bible are available. God does not change. The fact that He allows or permits humans to make choices does not mean He agrees with those choices He feels exactly the same way about wrong choices as He always has.