When it comes to zombies, there are three varieties, and of these three we can attribute their existence to one of two common origins. The three types of zombies are as follows:
TYPE ONE: The real-world zombies. These are living human beings, brain-damaged, the kind like Clarvius Narcisse, the kind investigated by botanist Wade Davis, an investigation that served as the basis for his nonfiction book THE SERPENT AND THE RAINBOW, which then served as the inspiration for the fictitious (and underrated) Wes Craven film of the same name. Alternately, they can be the flakka-crazed cannibals of recent headlines. The point being, they are living human beings and they really exist in our world.
TYPE TWO: The NIGHT OF THE LIVING DEAD variety.
TYPE THREE: The EVIL DEAD variety.
Types one and two share the same origin: Science. For the real-world zombie, it is a potent drug that “creates” them. For the zombies in Romero’s classic, it is radiation from a returning space probe, or perhaps an alien pathogen. There is a scientific, logical explanation for them.
Type three zombies are supernatural in origin, motivated by some unseen spiritual force.
Which do you prefer? Science or Supernatural?