Since you mention food supply, this doesn't have to do with human populations, but it's an interesting point nonetheless.
A while back someone pointed out that after the flood the predator/prey ratios would be way out of whack. The usual situation is that prey far outnumber predators. But after the flood, for unclean species there would be just one pair of each predator species and one pair of each prey species. The predators have to eat, and each they did they'd wipe out a prey species.
--Percy