According to Psychology Today, there are three basic reasons why humans choose practicing polygamy. They are as follows:
1- A scarcity of adult males, which could be caused by war or disease.
2- Women in disease prone countries may prefer men that are disease resistant such as healthy attractive males to father their offspring, leaving less desirable men without mates.
3- Males having economic resources and the wherewithal to defend their breeding territory, such as in countries where men could monopolize wealth whether in terms of earned income or farmland.
In the case of the Mormons, some of the leaders were allegedly practicing polygamy prior to the trek across the plains. The trek across the plains in the dread of winter, pushing handcarts and having a scarcity of food and cover depleted many of the male population. In many cases the males gave their share of food to feed their wives and children and their clothing to protect their families from the extreme cold. With nothing much more than a handcart and some blankets the pioneers trekked on, leaving many of the men and some children buried or laid out on the frozen turf. Those of the men who could financially and physically take care of the widows and their children took them into their families. After these pioneers settled in the Salt Lake Valley and surrounding areas one woman was heard to say that she would never watch a pioneer day parade because she hated the sight of handcars. Eventually the Government forced the Mormons to give up the practice of polygamy or have their temples and other properties confiscated by the Federal Government.
Practicing polygamy is out of place in the modern world as developed countries are highly urbanized. As a result it is very difficult to raise large families in cities, because children are a huge drain on finances that can last for twenty years. Polygamy works best in an agricultural society as the children defray the cost of raising them by contributing labor as farmhands or house maidens. In developed countries serial polygamy is common where a man divorces his first wife and marries another.
Plural marriage is much more common in the poor countries and in countries near the equator. Cultures that practice polygamy have a better chance in underdeveloped tropical countries, but not so well in the developed highly urbanized high latitude countries such as the USA and Europe. Why? Three factors are raised. First, instead of a scarcity of males developed countries have an excess thanks to better public health programs that save more men than women. Second, colder winters which make it impossible for mothers to raise children without a good deal of help from their husbands. Third, developed countries are highly urbanized making it extremely difficult to raise large families in cities, because children are a drain on finances making it almost impossible for most men to raise multiple families. Contrary to popular opinions, polygamy has nothing to do with poverty or backwardness.
Because Mormon Polygamy took place within the past 150 years and dissidents or Fundamentalists still practice polygamy today, I have referenced this practice as an example of modern day polygamy. It is this writers opinion that the Mormons would eventually have had to question the practice of polygamy, should the Government had not forced the issue. As the State of Utah became industrialized and urbanized, the agricultural society would have shrunk substantially. Thus large and multiple families would have become a drain on the finances of the polygamist families as children became liabilities rather than laborers on the farm. Also their would not be a scarcity of males giving the woman choices in finding husbands.
Although polygamy is banned and hated in developed countries, it is surprisingly common and popular elsewhere. Polygamy may be detested in developed countries, but it is practiced to some degree in many societies. As Christians believing in the Bible we find that some of our greatest prophets were polygamists. Abraham was promised by God that his seed would be greater than the sands on a sea shore.
The Mormon Fundamentalists or dissidents are isolated living in desert areas away from population or urbanized cities. Thus in the case of Warren Jeffs he can control the followers even from jail. Because of the lack of marriageable women the men prey on underage girls. To rid the colony of competition for the girls many of the boys are excommunicated from the colony for minor religious infractions. There are over 400 boys that have been left out in the desert to find their own way. These boys lack formal education and are unfamiliar with the outside world and as a result many are exposed to drugs and prostitution.