Just reporting not supporting:
http://www.gotquestions.org/polygamy.html
Question: "Why did God allow polygamy / bigamy in the Bible?"
Answer: The question of polygamy is an interesting one in that most people today view polygamy as immoral while the Bible nowhere explicitly condemns it. The first instance of polygamy/bigamy in the Bible was that of Lamech in Genesis 4:19 : “Lamech married two women.” Several prominent men in the Old Testament were polygamists. Abraham, Jacob, David, Solomon, and others all had multiple wives. In 2 Samuel 12:8 , God, speaking through the prophet Nathan, said that if David’s wives and concubines were not enough, He would have given David even more. Solomon had 700 wives and 300 concubines (essentially wives of a lower status), according to 1 Kings 11:3 . What are we to do with these instances of polygamy in the Old Testament? There are three questions that need to be answered: 1) Why did God allow polygamy in the Old Testament? 2) How does God view polygamy today? 3) Why did it change?
1) Why did God allow polygamy in the Old Testament? The Bible does not specifically say why God allowed polygamy. As we speculate about God’s silence, there are a few key factors to consider. First, there have always been more women in the world than men. Current statistics show that approximately 50.5 percent of the world population are women, with men being 49.5 percent. Assuming the same percentages in ancient times, and multiplied by millions of people, there would be tens of thousands more women than men. Second, warfare in ancient times was especially brutal, with an incredibly high rate of fatality. This would have resulted in an even greater percentage of women to men. Third, due to patriarchal societies, it was nearly impossible for an unmarried woman to provide for herself. Women were often uneducated and untrained. Women relied on their fathers, brothers, and husbands for provision and protection. Unmarried women were often subjected to prostitution and slavery. The significant difference between the number of women and men would have left many, many women in an undesirable situation.
So, it seems that God may have allowed polygamy to protect and provide for the women who could not find a husband otherwise. A man would take multiple wives and serve as the provider and protector of all of them. While definitely not ideal, living in a polygamist household was far better than the alternatives: prostitution, slavery, or starvation. In addition to the protection/provision factor, polygamy enabled a much faster expansion of humanity, fulfilling God’s command to “be fruitful and increase in number; multiply on the earth” ( Genesis 9:7 ). Men are capable of impregnating multiple women in the same time period, causing humanity to grow much faster than if each man was only producing one child each year.