Zombies are our monsters. We are modern and we are secular, so our monsters will be just the sort of creature that would terrorize a modern, secular audience. Because we believe in a strictly material reality, zombies can’t suggest any transcendent meaning; we really don’t go for that sort of thing.
Another one of the main features of movies in the zombie genre is that the origin of the zombie infestation is unclear. We simply do not know where they come from. The reason is that if they have a cause they would also have a meaning.
If they are clearly caused by scientific hubris, then the zombies are a warning to not be scientifically hubristic. If it is discovered that the dead have animated because of environmental degradation, then they mean we should stop driving SUVs. If it is discovered that the infestation is a disease, the zombie would represent the perpetual struggle of man against a hostile world. If they are the minions of an evil genius bent on world domination or created by aliens they symbolize an internal or external political threat, respectively.
Zombies refuse to explain their origin.
This motif was established in Romero’s Night of the Living Dead, and it is true of almost all the stories of the undead that follow. Within the story, various theories as to why corpses have re-animated are sometimes suggested: “human error might be the cause, so might the space program, extra-terrestrial forces, ‘natural’ conditions in outer space, and so on” (Waller 275-6). But the cause is almost never certain.
And that’s because it’s not important, nor is the plausibility of that cause, since the movies are really always about the effects, not the causes, of the zombie infestation.
To offer some rational cause for the walking dead would give meaning to the calamity.
In fact, Italian director Lucio Fulci is “not afraid to throw aside logic or narrative.” In his film Zombie 2, for instance, the cause of the zombie infestation changes from a pagan curse early in the story to some form of contagious disease later in the film. This disregard for consistency shows that “the central concern of zombie films has nothing to do with . . . discovering the ultimate cause of the catastrophe”(Zani [Better off Dead] 108).
To offer some determinate cause for the walking dead would give meaning to the calamity. The search for the cause would end up being a search for the meaning of the zombie within the context of the film, and this is precisely what the zombie film will not do—the lack of meaning is at the heart of zombie narratives.
A consistent ambiguity surrounding the cause of the zombie infestation, both within or between movies of this genre, places the attention on the immanent struggle of the human protagonists and away from a cause for which even transcendent explanations would have to be too seriously considered. When we stopped living in a world enchanted by the supernatural, we lost supernatural purpose and meaning. Meaning, if it is to be found, will be found inside oneself. But that means there are as many meanings as there are people, or at least groups of people. It’s as if, out of respect for our unwillingness to impose some universal truth on anyone, zombies refuse to mean anything.
I would argue that if we do know the source of the zombie infestation in a particular movie, then it has broken from a significant marker of zombie narratives.