I was reading this article on polygamy in the Maasai of Kenya (as well as among other traditional east African groups). The article appeared to suggest that polygamy is quite common amongst the residents of the Rift Valley, and I've heard other accounts of polygamy across Africa in traditional communities. For example, South Africa's president Jacob Zuma has multiple wives in accordance with Zulu tradition.
My question is: how do these societies where polygamy is common sustain the cultural practice? Simple math would appear to indicate that if a significant proportion of men regularly take multiple wives, there will soon be a large population of (presumably) angry single men who would resent and fight against the system, given that humans are born in roughly even birthrates? (Indeed, the natural human birthrate tends towards more males. Yet, I've seen nothing to suggest this being a problem for traditional polygamous societies. Do these societies kick out or kill young men? Is there simply a high death rate for men? How can polygamous society avoid massive social rifts between those with wives and those without?
There is evidence that in the US, this practice exists in the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS), an offshoot of the of the Mormon Church, or LDS. Men (or boys actually) are kicked out of the community so they do not compete with other males who are "chosen" by the leaders to have multiple wives. They are called "the lost boys".
There are multiple websites about this practice. Here is one article, here is another, and here is one from the National Geographic where an official of the FLDS admits the practice did exist but claim it has been stopped.