n science fiction, it's almost a cliché that the dead won't stay dead. Whether they're revived by the technology of mysterious elder races or uploaded into a new body, flash-cloned from skin cells and genetically encoded memories or resolidified from stored transporter patterns, the end result is the same: a perfect, smiling new version of the deceased, indistinguishable from the original. Sometimes there's a bit of amnesia or disorientation, but if so, it's usually complemented by strange new insights brought back from the other side. In their White Rider personae, the Kirks and Spocks of the world know exactly how to win the day, at least until sequel time, when it's the villains' turn come back from the dead.
In horror fiction—even comedy-horror fiction like Tim Burton's wonderful Corpse Bride—things work a little differently. Raising the dead is an act of questionable morality, because they never come fully back to life. They turn into ghouls or vampires, liches or ghosts—creatures with unnatural desires, unnatural powers and only the dimmest memory of their former selves. The ghastliest of all, and the most common in modern American lore, are the zombies: creatures with the power to see and hear and walk, but only limited powers of reason. Stripped of fear and love and even anger, trapped in bodies that continue to decompose, zombies feel nothing but an endless, burning hunger that only human flesh—especially brains—can fill.
Now, we've all heard the warnings about Abominations Against Nature and Things Man Was Not Meant to Know, but if horror movies have taught us anything at all, it's that we simply can't resist the temptation. Show us how to make a zombie, and the first thing we'll do is try the recipe to see if it really works. And if curiosity is such an integral part of human nature, can we really be held responsible for the consequences, however dire?
Mary Shelley had the right idea
The first thing to recognize here is that "zombi," a Congolese word meaning "charm" or "fetish," refers to an actual practice from the old, dark magic of the vodoun religion. Pufferfish—those piscene sea critters that swell up into a spiny ball when frightened—contain a concentrated bacterial toxin called tetrodotoxin that, even in doses as small as 0.1 mg per kilogram of body mass, causes paralysis and death in humans. Simply touching the meat of this fish can be fatal, although with years of specialized training, a Japanese sushi chef can prepare it as fugu, a tasty, euphoria-inducing side dish for culinary thrill-seekers. In the hands of a voudoun witch doctor, or houngan, though, the fish is dried, ground up into a powder and used to poison enemies.
Amazingly, though, the enemies don't always die. Sometimes they're placed into a cataleptic state where there's no measurable respiration, heartbeat, pupil dilation, pain response or other sign of life. The victim appears dead, so bereaved friends and family pack the body into a coffin and bury it. Horribly, though, the victim remains conscious throughout this time, able to see and hear and feel what's going on around him, but unable to move, speak or even breathe. Small wonder if they, too, believe themselves to be dead! Anyway, under cover of darkness the houngan digs up the coffin, awakens the "zombi" with a cocktail of drugs and a tale of dark witchcraft, and then spirits the frightened (and often brain-damaged) person away to work as a slave on a plantation somewhere. In days gone by, these zombies sometimes found their way back home to their families, only to be turned away again as unclean, undead monsters! This grisly practice continued in Haiti until surprisingly late in the 20th century, and may actually still be going on there or in parts of Africa.
So let me clarify that when I talk about zombies here, I'm not talking about vodoun medicine. I'm also not talking about sleepwalkers, pot smokers, infection with the 28-day "rage virus" or anything like that. I mean actually dead people brought back to an actual (if slightly horrid) semblance of life.
Mary Shelley may have had the right idea when, in 1817, she observed the twitching of dead, severed frog legs in response to electric shock, and then ran home to pen the novel Frankenstein. Unfortunately, while dead muscle fibers really will contract in response to a few milliamperes of current, they relax again when the juice is turned off. They don't get up and walk away. If you attached a defibrillator to a dead person's chest and kept on shocking with it, you probably could keep the heart beating even if the heart tissue itself was dead. This would pump blood through the body, and if you included some kind of respirator, you could make sure that the lungs kept this blood well oxygenated. Unfortunately, even if you get the heart and lungs working again, the tissues of a dead body have little use for oxygen. By themselves, they won't take it up and come back to life.
On the other hand, while many higher brain functions are irretrievably damaged after just minutes of cardiac arrest, most of the actual tissue remains "metabolically active and responsive" for at least 24 hours after death, and the hard wiring between neurons probably doesn't change until actual decay sets in. This raises an interesting and somewhat chilling question: What's the subjective experience inside a "dead" brain that continues showing low-level electrical activity for hours or days afterward? This is more than idle daydreaming (or idle nightmaring), because there are also neural pacemakers—intended mainly to treat epilepsy—that introduce small electrical shocks into the brain. A dozen of those would get some interesting currents flowing through the dearly departed neural tissue, and if you networked them with a bit of computing power, and connected them to electrodes on the arm and leg muscles, you might even get something that could "think" and "feel" enough to drag itself along the ground.
But that's cheating, right? In the first place, it's more of a golem than a zombie, and if you press the idea hard enough, you'll simply Borg out the corpse, replacing its missing organic functions with mechanical ones. Building a robot on top of a meat chassis, in other words. This is a cool idea, but if we're looking for actual zombies, we need to look a bit deeper.
Zombochondria can be contagious
"Death" is really just another word for the start of an irreversible process, and the first major change that occurs seems to be in the cells' power plants, or mitochondria, whose membranes quickly come apart like Humpty Dumpty and can't be put back together again. Without mitochondria, the cells can't consume oxygen or produce ATP, the chemical fuel used by the rest of the cell, and without ATP, the cell can't perform its normal functions. The game isn't over, but it's locked in a permanent pause that lets other, more sinister forms of decomposition set in over a period of hours and days.
If we could somehow get a jolt of ATP into every cell in the body within the first few hours after death, then the cells should start right back up and the body should "live" again. Unfortunately, the cells would use up their ATP within minutes and we'd be right back where we started. What we need is a way to replenish that ATP on an ongoing basis. What we need, in fact, is something that acts exactly like a mitochondrion but doesn't die when its oxygen supply is temporarily interrupted. This is actually easier than it sounds, because there are pathogenic bacteria that produce ATP for their own use in both aerobic (oxygenated) and anaerobic (oxygen-free) environments. Some, like the "rickettsia" that cause Rocky Mountain spotted fever, are also capable of invading a living human cell and setting up shop there as parasites, so all we'd need is a minor mutation to force the microbes to overproduce ATP.
This is a promising avenue for zombie research, because Rocky Mountain spotted fever, like zombieosis, is not an airborne pathogen; it can survive only when transmitted by bite. If our zombie bug invaded healthy tissue, it could slowly poison the mitochondria (causing death within a few hours) and then take over their function once respiration stopped. If it invaded already-dead tissue, its job would be even easier because there'd be no immune system to fight off the infection. Actually, while these "zombochondria" were reactivating various systems in the body, they'd quickly deadlock the immune system, because as immune cells came back to life they'd try to kill off the very organisms that were keeping them alive! Thus, the zombie would have no immunity and would slowly rot like any other dead meat.
Now, zombies are clearly capable of breathing, because they can groan, screech and sometimes even speak, so presumably there'd be some oxygen coursing through the system for the zombochondria to use (though probably a lot less than in a living person). However, according to Return of the Living Dead, Part II, zombies have no heartbeat and can survive indefinitely underwater, and according to Dawn of the Dead they can continue attacking even if all their blood is drained out. This implies a very robust anaerobic metabolism, probably powered by the fermentation of fat. (This would also explain the particular hunger for brains, which are 60 percent fat by volume.) Zombochondria would be a lot harder to kill than mitochondria! We should expect a bloodless, breathless zombie to get tired more easily than its oxygenated brothers, but that's OK. Slow and steady wins the fight if numbers are on our side.
Zombochondria don't even need to be as efficient as mitochondria. Walking requires balance, and balance requires the brain to translate sensor readings from the inner ear into muscle commands for the feet and legs and torso. This operation happens about 20 times a second in a highly trained athlete, although five times per second is sufficient for a toddler, a clumsy robot or a staggering, shambling zombie. So restoring 25 percent of brain activity, and probably a comparable amount of muscle function, should be sufficient to get our first zombie on its feet. As for higher brain functions, hey, when all you do is eat, the mental capacity of a grasshopper is all you'll ever need. Just remember, the zombie will last only a week or so before going bad like the leftovers in your fridge, so if we want to get a global zombie plague rolling, we need to set him loose right away.
Do I personally know how to mutate Rocky Mountain spotted fever bugs into zombochondria and use them to raise the dead? Sadly, no. But Science Fiction Weekly's readers are numerous and clever, and with a bit of luck I can maybe point a few of you in the right direction, just in time for Halloween. If you succeed, don't bother emailing us; just shamble on by and say "Uuuuuughhh!"
Sources:
Wikipedia: ("tetrodotoxin,, "zombies," "Frankenstein"): en.wikipedia.org
Interview: Richard M. Powers, Ph.D.
Interview: Virginia Bush, M.D.
Cronin, Joe, et al.: "Control of a Heavy Weight Biped Robot in the Frontal Plane," School of Mechanical and Manufacturing Engineering, The University of New South Wales
"Rocky Mountain Spotted Fever," www.cdc.gov/ncidod/dvrd/rmsf/Organism.htm
Merkle, Ralph C.: "The Molecular Repair of the Brain," Cryonics magazine, Vol. 15 #1 & 2, January and April 1994
Peter R. Dodd, John W. Hambley, Richard F. Cowburn and John A. Hardy: "A Comparison of Methodologies for the Study of Functional Transmitter Neurochemistry in Human Brain," Journal of Neurochemistry, 1988
"Brain Pacemaker May Prevent Epileptic Seizures," www.cnn.com/HEALTH/9908/25/brain.pacemaker/
The American Heritage Dictionary of the English Language, 1980 edition
Davis, Wade: The Serpent and the Rainbow, Simon and Schuster, 1985
The Encyclopedia Britannica Ultimate Reference Suite, 2004 Edition ("Iceland")
Wil McCarthy is a rocket guidance engineer, robot designer, nanotechnologist, science-fiction author and occasional aquanaut. He has contributed to three interplanetary spacecraft, five communication and weather satellites, a line of landmine-clearing robots and some other "really cool stuff" he can't tell us about. His short writings have graced the pages of Analog, Asimov's, Wired, Nature and other major publications, and his book-length works include the New York Times notable Bloom, Amazon "Best of Y2K" The Collapsium and most recently, To Crush the Moonn. His acclaimed nonfiction book, Hacking Matter, is now available in paperback.
