A zombie stalks its prey: attracted by the smell of living flesh, it follows slowly but inexorably, undeterred by damage to its rotting body, until it feasts on its victim’s still-warm brain. This is pure science fiction—right?
It turns out the idea of living dead—depending how you define both “living” and “dead”—may not be as far-fetched as it might seem. Some science fiction writers have found inspiration—and trepidation—in real-life parasites. We talked to two of them, Mira Grant and M.R. Carey, about their newest books and the concept of scientific zombies.
In M.R. Carey’s The Boy on the Bridge, the companion novel to his bestselling The Girl with All the Gifts, the living dead are called “hungries,” and they’re caused by a fungus called Cordyceps, which exists in the real world—though it typically attacks ants. “By means of fake nerve signals, the fungus takes control of the ant’s body,” Carey explains, “which it then uses to assist its own propagation. In my novels, a mutated version of Cordyceps turns humans into hungries, shutting down their higher brain functions and filling them with the irresistible urge to bite into and feed on live flesh, which of course spreads the infection.”
Carey searched for a pathogen that met his criteria for the cause of the hungry epidemic, and realized that Cordyceps fit perfectly. It was also a unique choice. “At the time nobody had ever used a fungus as the vector for a zombie plague,” he says, though the creators of a console game called The Last of Us came up with the same idea independently, around the same time.
Mira Grant is the author of the bestselling Newsflesh series, including, most recently, Feedback. There’s a key difference between the zombies of the Newsflesh series and those of most other stories about the walking dead: they’re technically alive. “They’re called ‘zombies’ because my world is set after the Romero movies were made, which means that people started getting up from fatal accidents and attacking and eating the people around them, folks went ‘it’s zombies,’ and it stuck,” she explains. “That got us past a lot of the basic biological implausibilities.”
An interesting quirk of her zombie epidemic is that animals can be infected, too. The virus “infects all mammals, but is only able to reach sufficient viral mass to cause amplification—i.e., conversion into a full zombie—in creatures of forty pounds or more.” Consequently, very few people in the Newsflesh world keep domesticated dogs or horses.
Grant reads a lot about virology and epidemics. “Viruses are amazing,” she says. “There’s a lot of real research going into the idea of modifying viruses to make them work for us.” In Feedback and the Newsflesh series, viruses intended to cure cancer and the common cold combined, causing unintended consequences.
In preparation for writing his novels, Carey read texts on parasitology and some recent scientific studies, but he cites as his most important source David Attenborough’s Planet Earth. “Attenborough’s team used time-lapse photography to show Cordyceps growing out of the bodies of infected ants, which is one of the most terrifying things I’ve ever seen.”
Besides reading, Grant also “spent a lot of time on the phone with the CDC, which was an incredible amount of fun.” Grant savored the information she gleaned that way, but her friends “had to make new rules about what I was allowed to discuss over food,” so they didn’t lose their appetites.
Both Grant and Carey admit that their zombie tales require some leaps of imagination. “Science fiction science is not the same as ‘real’ science,” Grant says. “Good science fiction science builds on real science, uses the principles of real science, but it’s allowed to make ‘suspension of disbelief’ exceptions.” Carey puts it even more bluntly: “It’s a mixture of reasonable science and impossible magic thinking.”
So zombies exactly as we imagine them in fiction aren’t likely to happen. But don’t breathe a sigh of relief just yet; both authors know enough about real-life pathogens to leave you uneasy.
“There are diseases in the world, right now, that can cause erratic and unpredictable behavior,” Grant points out. “Rabies takes over. Rabies drives the meat car wherever it wants to go. Could there be a disease that caused a slow response to pain, violent behavior, and an eventual loss of rational thought? Yeah, I’ve got a couple I could show you. Honestly, the only reason we’ve managed to dodge the bullet, as it were, for this long is that most of the diseases that really go after the brain aren’t airborne.”
Carey is no more reassuring. In a sense, “it may have happened already. Toxoplasma gondii, a bacterial parasite on cats, can successfully infect a human host—and there’s some evidence that once it’s in your system, it’s able to influence your behavior.” Toxoplasma makes mice less risk-averse, and that behavior is passed onto the cats that consume them, and can then be passed to humans. “The mouse will lose its aversion to the smell of cats. A few studies have suggested that infected humans have a similar difficulty in making good decisions about imminent risks—for example, that they’re more likely to be in automobile accidents, whether as drivers or as pedestrians. This is controversial stuff, and far from proven, but I don’t have any difficulty at all in imagining a zombie plague brought about by a parasitic fungus or bacterium.”
If you’re now feeling compelled to prepare for the zombie plague, we’ve got some reading for you. Feedback by Mira Grant and The Boy on the Bridge by M.R. Carey were both picked as best books of the month in the science fiction and fantasy category, and they are available now in print and Kindle editions.
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