I'm sorry religion is not actually the main cause of war so that's not even worth mentioning, as mentioned MANY times most of the "real" Modern wars (I mean ones involving whole countries and not just individual tribes fighting one another which Last i heard falls under the catagory of "Conflicts other then war)have been caused over the desire for Raw materials, land and other resources.
Banishing all religion would NOT bring peace at all, especially since nation's that have "Banned" religion have simply taken up humanistic "divinity" as their new dogma, or used the ban on religion as an excuse for promoting their own dogma.
Basically religion as the cause of all war is just an excuse atheists use to make those with religious belief look bad. (aside from the 7day war I mean point out a war now a days caused by religious beliefs? (seriously if there is a war I don't know about point it out I'm willing to listen)
A unified world government would probobly require the unification of the super powers first (AKA China and the US would have to ally) and then most likely a big nasty war to get rid of those irritating nationalist Groups that would no doubt pop up when you tried to take over their country either by economic or military preasure. Ah hell I'm going to start a thread on this
read that to see the rest of this hehe.
Oh and I probobly misunderstood the whole Chinese population growth thing I know that at one point in history their population doubled every fifty years.