Sadly, the Undead Can't Exist

There's a mathematical argument for why vampires and zombies are impossible. Essentially, the speed with which they would need to feed and reproduce would outstrip human's ability to reproduce, so the number of zombies or vampires (or maybe zombies and vampires, 'cause then we could have undead wars, which would be awesome) would rapidly overwhelm and wipe out the human population. (For details, click through here.)

I think we can know safely divide the world into four groups:

1. those who find this convincing evidence that the undead cannot exist,
2. those who are not convinced by the mathematical proof,
3. those who find it silly to engage is such proof, and
4. those who say, "What about werewolves?!"