Except that the Earth isn't overpopulated yet.
What makes you say that?
IIRC if you compare the average first-world citizen and the land area he or she indirectly consumes (farmland, etc.), if you multiply it by the world population you go past the area of fertile/useful land in the world (even assuming we gut the Amazon and such more than we already have). So at the very least, we're overpopulated if we want to maintain this standard of living.
(Of course if vegetarianism took hold in a big way we'd be fine in this regard.)
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