Phil Plait is an astronomer and major sci-fi geek. He writes the Bad Astronomy Blog for Discover Magazine and is also the host of the Discovery Channel's science show "Phil Plait's Bad Universe." You can follow him on Twitter at @BadAstronomer.
It's Halloween, and I'm a geek, which means BRRAAAAIIIINNNNSSSS ...
Pardon me [stifles a belch]. I of course meant zombies. I like all kinds of monsters (with maybe the exception of vampires, which never really appealed to me, sparkly or otherwise), but there's just something about zombies that make them truly creepy.
Their popularity is on the rise, too, and with this resurgence of shambling brain-eating walking dead comes the annoyance I get every time I start a new zombie book or movie: Are these guys going to be supernatural or scientific?
Don't get me wrong: Even as a dyed-in-the-lab-coat skeptical scientist, I'm willing to suspend my disbelief long enough to enjoy a good tale or two. But the problem is, too many zombie stories are inconsistent, wrenching me away from the fantasy and back into our sadly zombie-deficient real world.
When it comes to zombies, you really have only two choices: the dead walk the earth due to some mystical power that we cannot fathom, or through some ultimately scientifically testable manner such as a virus, cranial computer chip or radiation. But each has implications, and these routinely get ignored.
Now let me back up a sec here and ask a funny question: What exactly is a zombie, anyway?
Don't laugh! It's not all that easy to answer. Ignore all the mumbo-jumbo history of where the word came from and all that (though it's interesting and worth reading about); I mean in stories, what makes something a zombie? If it's just a body that's been reanimated, then technically Frankenstein's monster is a zombie, and I don't think that would sit well with anyone. So maybe it's a reanimated corpse that eats brains? Well, I'm not sure that fits either. The bad guys in 28 Days Later were generally thought of as zombies, but it wasn't clear they ate their victims; they just tore them apart. Same goes for I Am Legend.
I'll also spare you the shambling-versus-running slow/fast zombie wars. I think it's a cool twist that zombies—whatever they turn out to be—can run quickly. Shuffling zombies are only scary in large numbers or enclosed spaces, limiting their ability to hunt you down and eat whatever organs they happen to prefer.
Whatever they are, maybe we need to define them as "know them when we see them." Trying to nail down a definition is as hard as defining what a planet is, and don't get me started with that! Let's just say they were once people, but have been changed somehow through death or attrition or some other vector that makes them more animalistic and willing to partake of long pork.
No matter what, the important thing is how they got where they are, and what you should do if you happen to be running from one or a horde of them. And that depends on whether they're sciency or supernatural.
As an example: in the classic Night of the Living Dead, George Romero wisely avoids the science/supernatural issue, only giving oblique reference to radiation from a downed spacecraft. Since it's issued as a news report, it may be a total red herring.
His zombies move slowly, eat anything they can and die if the brain is destroyed. Sawing a Living Dead zombie in half might slow it down, but it'll still use its arms to crawl after you. And even severed heads have been known to snap at the still-living.
But does that make sense? Scientifically, well, no. Our brains are power hogs. They need a lot of energy to run: your brain uses about 20 percent of the energy budget of your entire body, despite being only 2 percent of your weight. That means a brain needs a lot of oxygen if it hopes to work at all.
Now, perhaps in a zombie the amount of power a brain consumes is lessened somewhat; it's not like they need a huge energy reserve to bumble around and mutter "brraaaaiiiinssss" and eat people. Still, a brain does need an energy source, and that comes from oxygen and nutrients in blood. No heart and no lungs makes Fido a dead zombie. Dead dead.
So if you want a scientifically viable zombie, there must be something else powering the brain. But what, exactly? It's not like there's a zombie that can run on a gas engine or solar cells. Max Brooks gets around this somewhat in his World War Z zombies, positing a virus that somehow kills the host but still animates it, mutating the brain into a new organ, but even then the details of an energy source are never clear.
Even assuming an energy source for the brain, there's still the matter of the energy needed to move, digest the ill-gotten human meat, and so on. I'll note that in a lot of zombie stories, the corpse will rot. That much, at least, is true: Without an active immune system, any number of bacteria, parasites, symbionts and such in your body will happily consume your corpus delectable. But if the story features a decaying zombie, it also tends to ignore the other implications of an inactive cardiovascular system.
I suppose, then, the only way to have a scientific zombie (and by that I mean a scientifically viable one, not a zombie in a white lab coat peering through a microscope) is for all the major organs to be working, so that the brain can get the energy it needs. In that case, a shot to the heart, or the spleen, or piercing a major artery, will bring it down as well as a head shot.
... but you may see the problem here. If all the major organs work, and the brain works, it's not really a zombie, is it? In that case, we're back to the poor things in 28 Days Later. Not really zombies, but kinda sorta resembling them. In the "brain-eating-walking-dead" category, then, I suppose there's no such thing as a science-based zombie.
So if science has abandoned us, that leaves supernatural. I'm all for that, but still. If you assume some sort of magical potion or incantation or otherworldly energy source is what gives zombies their lethargic zest for flesh, then again why the head shot to kill them? If it's really magic, they should be good without a head, just as they would without a heart or lungs or spleen.
To be fair, that's been the case in some movies. Who can forget Carl Hill's decapitated corpse in Re-Animator? I won't go into details about what it does, but the head does appear to have some, uh, earthly passions, and the body has some will of its own as well. That movie is scientific in its depiction—it's a potion that does the zombification—despite the clearly unscientific premise. We still have the same brain power issue ... not to mention the problem of how a severed head talks.
[Badly. Badda bing!]
Going through my list of books and movies, I haven't seen any that have classic reanimated-corpse-style zombies that treat them correctly and consistently. Maybe there's simply no way to do it and make a good story. Or maybe no one's tried yet.
Or, it's possible I just missed it. I can't watch and read every zombie story that comes along. If I've missed one, then please—to paraphrase Return of the Living Dead—send more ideas.
Phil Plait is an astronomer, geek and sometimes-movie-curmudgeon. If he ever writes a zombie novel, one of the characters will be named Sarah Bellum.