I had a great question from a colleague last week and, since I have been admittedly negligent in dealing with the issue of zombies, I'd like to take some time to discuss this important subject.
The question: Wouldn't zombies decay rapidly in the heat of summer or freeze solid in the winter for easy killin'?
Basically, most zombies are re-animated corpses. They can be roughly divided into two categories based on the type of re-animation, those of supernatural origin and those of scientific origin.
The original zombies come from African folklore and are the former type, re-animated by witchcraft and, therefore, not really worthy of scientific discussion. A puppet master, such as a witch doctor, controls this type of zombie so it is entirely possible it could be imbued with other unscientific characteristics such as the inability to naturally decompose.
Today, zombies have proliferated in modern pop culture largely because of George A. Romero's seminal 1969 film Night of the Living Dead. Like Romero, some makers of zombie flicks ignore origin and details such as decomposition giving them complete freedom to imbue their monsters with plot-convenient characteristics. Even so, some movie zombies of unknown origin-Dawn of the Dead (2004), Zombieland (2009)-decompose at normal rates, and would presumably freeze as well. In this case, the obvious strategy for the uninfected is to be prepared and wait out the zombies, but more on zombie apocalypse preparedness later.
More recently, it has become popular to give zombies scientific origins, usually some kind of virus. I personally think bacteria are more likely culprits. Some bacteria species in the real world are known to act as single organisms, so if there is a chance for some foreign parasite to re-animate a corpse, this makes more sense to me. I digress.
The short answer to the question at hand is: it depends on the type of zombie.
That leaves the problem of re-animation. Is a human zombie scientifically plausible?
For the answer to that question, we turn to nature, specifically the life cycle of Euhaplorchis californiensis, a tiny parasitic worm that lives in the saltwater marshes of southern California.
This little badass relies on three different hosts to complete its lifecycle. Adult E. californiensis live in the bellies of shorebirds where they lay eggs. The eggs are transmitted to the marsh through the birds' droppings, which are consumed by snails.
In the snail, the eggs hatch into larvae that swim out into the water and catch a ride on the gills of killfish. The larvae then make their way along a nerve to the brain cavity of the fish where they form a layer on the brain effectively turning the fish into zombies.
The parasite forces its host to swim to the surface and thrash around making it easy prey for birds. Infected killfish are 30 times more likely to be eaten than their un-zombified counterparts.
Of course, the killfish is still alive when it exhibits its zombie-like behaviour. Real human zombies would likely follow a similar pattern.
Nevertheless, one could postulate a scenario under which re-animation of a corpse could take place, however implausible. The human body relies on commands from the brain transmitted via motor neurons in the spinal cord to move its muscles. If a person were dead, she would require an alternate mechanism to achieve movement.
As I mentioned before, scientists are starting to unravel the secrets of certain species of bacteria that appear to be able to communicate and work cooperatively. Could such an organism infect a dead host and mimic its body functions? I don't know, but it could certainly make good science fiction.
And, I suspect such a zombie would likely move spastically and slowly. It would also very likely decompose at a normal, if not elevated, rate so the parasite would need to find new hosts. However far-fetched, sounds like a recipe for zombie apocalypse to me.
It doesn't hurt to be prepared.
In 2011, anticipating the upcoming hurricane season for that year, Rear Admiral Ali S. Khan, director of the Office of Public Health Preparedness and Response for the U.S. Centre for Disease Control and Prevention (CDC), wrote a blog post entitled "Preparedness 101: Zombie Apocalypse."
"Take a zombie apocalypse for example," Khan wrote. "You may laugh now, but when it happens you'll be happy you read this, and hey, maybe you'll even learn a thing or two about how to prepare for a real emergency."
It started out as a tongue-in-cheek blog post, but was so effective in reaching new audiences, the CDC has since turned it into full public awareness campaign. This year, the organization even published a graphic novel with the same title as the director's original blog.
Says Khan: "If you are generally well equipped to deal with a zombie apocalypse you will be prepared for a hurricane, pandemic, earthquake, or terrorist attack."
