Overpopulation is definitely at the top of the list, when it comes to the driver of our world's ills. Regarding involuntary sterilization as a remedy that could be implemented to solve current, rapidly rising population growth, I doubt this solution would be tolerated by the peoples of the industrialized afluent nations, let alone the struggling third world citizens. And if a government or power structure tried to force this particular solution on any large populations, I think that this endeavor would create a great rebellion in the people being affected. Such is the quandry of just how to control runaway population growth. If Oil and Natural Gas do reach thier peaks of production soon, as many indications are showing, then the most intense driver ( hydrocarbon fuels ) of humanities recent population increase will begin its inexorable decline, and if alternative forms of energy are incapable of filling the gap of lost hydrocarbon energy resources, then mass dieoffs will certainly occur. A nuclear war on any level would be devestating, so hopefully humanity can avoid the senario of something like that. There are so many differant factors at play in world events that will also affect our future, like Climate Change. One way or another, population will be controlled, and I think its more than likely, that Mother Nature and/or mans propensity towards violence will do the deed.