Yahtzee Croshaw said:
Extra Punctuation: Why We Love Zombies
Yahtzee's got four good reasons why we love any book, movie or game that has zombies in it.
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I think it goes beyond the "wish fulfillment" aspect, though. Mostly, I think reasons center around #4, our tendency to be interested in all things apocalyptic.
Zombies are the ultimate doomsday scenario. Robots, aliens, disease, meteor, nukes, all of these have a lot of pull... but zombies combine their best (worst) elements and add a few of their own:
1) The zombie apocalypse is longer and more trying on the human spirit. Unlike robots, meteors, or nukes, zombies aren't a one-off event resulting in sudden and catastrophic destruction. After the nukes, survivors rebuild in the ashes (or a safe distance from them)--the world is set back to the stone age, but hey!, the nukes are gone. The zombie problem only gets
bigger with each person that dies. The fallout never stops, and it has legs and teeth.
2) The zombie war is a losing battle. Each one we kill is just one less zombie. Each man we lose
makes their side bigger. The tighter we band together, the greater the chance that a single case could explode again through the densely-packed populace.
3) The zombie world is a hopeless one. The dead, despite every religion's beliefs and sacred rites, are rising and feeding on the living. Every religion just got proven wrong. So now, with things so bleak, people can't even hide in the folds of God's robe. They have to face it alone and in the stark knowledge of their mortality and insignificance.
Beyond this, there's also the hope that every geek can prove himself useful in the zombie apocalypse by having encyclopedic knowledge of the problem, but it still won't get them laid much because all the hot women will have been eaten.