In Utah, women used to marry young. In particular they married Brigham Young, leader of the Mormon Church. The religious leader had 55 wives by whom he had 56 children before he died, aged 76, in 1877. His followers had similar polygamous marriages.

But scientists have now uncovered an odd fact about 19th-century Mormons: the more women in a household, the lower the average birthrate. In other words, the more sister-wives a Mormon woman had, the fewer children she was likely to produce.

"Although it is great in terms of numbers of children for successful males to have harems, the data show that, for every new woman added to a male's household, the number of children that each wife produced goes down by one," said biologist Dr Michael Wade, of Indiana University.

http://www.guardian.co.uk/science/2011/feb/27/mormon-polygamists-fruit-fly

Plus, the odds of the children surviving and thriving go down as well. The speculation is that Daddy is more concerned with adding to his harem than he is to providing for and safeguarding his offspring. The result? Daddy's genes have a better chance of being successful but Mommy's don't.

Pay attention, women -- polygamy is counter-intuitive to your genetic survival. ;)

My husband cannot understand why a man would choose to have more than one wife...He says one is enough trouble :)

Polygamists don't. It's all about THEM baby. ;)