Mankind has spent a healthy amount of its history trying to make its place in the natural world a comfortable one. In World War Z, a couple brain-craving zombies show up and undo all that hard, hard work. Like a hurricane or plague, the zombies knock us out of our civilized trappings, forcing us to confront the natural world on a level playing field. To make matters worse, our survival instinct has dulled so much that we're horribly, horribly out of practice dealing with nature in our day-to-day existence. Add to that those zombies we mentioned, and things aren't looking so good for us.