The Natural History of Zombies

Zombies have eaten their way into our brains. From the halloween party at your neighbour's to the plots of major Hollywood features, they've become part of our culture. But is there some kind of reality behind the vulgar scenes of flesh-ripping re-animated corpses we are exposed to through popular media? Is there any way for scientists to create real zombies? The notorious science punk Frank Swain made it his mission to explore the science behind the walking dead, and the brain-child of his in-depth investigation is the book “How to Make a Zombie” (OneWorld 2013).

Unlike creatures like vampires and werewolves – who have inhabited western myths and fantasies for quite some time – zombies did not take their place in the western bestiary until the first half of the 20th century. In search of the origin of zombies, Swain dives into Haitian mythology. Here he is following the trail of earlier explorers who became fascinated by the darker sides of this cultural melting pot. We get to read about the first time a foreigner met with a so-called zombie, working in a field. When he tried to establish eye-contact it was like staring into the “eyes of a dead man, not blind, but staring, unfocused, unseeing”. Such reports led the zombie straight into popular culture. Their silver-screen début “The White Zombie” was released as early as 1932. But where’s the science?

Both mind control and reanimation had been the objectives of scientific endeavours, and the stories about the zombies of Haiti did not go unnoticed. Several research programmes were embarked upon, many crossing the line of what is considered ethical today. All attempts at fully controlling the mind of another person, or genuinely reanimating the body of a freshly deceased animal met with failure. So it seems like we’re safe, so far, from the possibility of a mad scientist creating an army of undead warriors. Nevertheless, the danger of falling under the influence of another organism is not nearly as remote. Other humans might not be our biggest threat in that respect, but rather parasites – and one of them might already be altering your behaviour.

We are surrounded by biological entities that make thier living by invading the bodies of others. Many have the potential to gain access to the brains of their hosts and manipulate their behaviour. Perhaps it’s because I’m a biologist by training, but I find the part of the book dealing with parasitic mind control to be the most fascinating one. Altering people’s behavior by mixing drugs and creating illusion, or by plane old mental illness, are all well and good. However, parasites have already mastered mind control. The Emerald Wasp can dictate the will of a cockroach by releasing a surgically precise volume of venom at exactly the right place in its brain. In that respect, zombies do exist: they are animals who have lost the control of their own bodies, puppets for the parasites to master.

Things get creepily close to home when Swain describes the influence of the one-celled parasite Toxoplasma gondii – because this is a parasite that might be in your head right now. Although Toxoplasma rather end up in a mouse brain than in yours, it still seems to behave in a similar way inside your head as it would in the brain of a mouse. There, it removes the mouse’s inherited scare of cats as a part of its plan to get eaten – the parasites final goal is to end up in a cat’s body where it will breed. Our sanity is such a fragile thing, easily broken not only by our own intrinsic biological processes but also by unwanted guests in our brains. Toxoplasma may not be the most vicious of parasites and its effects may be rather subtle, but it does make us more prone to risk-taking behaviour. So is the mad driving and other acts of seemlingly illogical behaviour that some of us display the result of our own conscious decisions, or is it the parasite in our brain that makes us do it? Who knows, today’s Toxoplasma infection in humans might be the first small steps on the way towards the zombie apocalypse.

• Zombie fiction in the bookshop