Every zombie movie has a terrifying underlying message. The enemy isn't supernatural or an alien from another planet. "The enemy is . . . us!" The "undead" -- mutated humans, grotesque versions of their previous selves -- are destroying everything in their path and bringing about the downfall of civilization. Even worse, they are contagious, gradually absorbing the few survivors left into the hoard. In Spiteful Mutants, evolutionary psychologist...