We can not, it was possible for us to live much longer way back hundreds of thousands of years ago, because of the earths atmosphere, people were much bigger, and animals were too. (big ass dinosaurs).
Now the atmosphere's ozone is breaking up to much due to pollution, so the sun's radiation is slowly poisoning us, so we are unable to live for aslong, or develop as we once did long time ago.
oh btw dude, dont worry about the worlds population getting bigger u will find out in a few years what the bush administration and practically every large government in the world has planned.
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