The science behind our monster myths

It’s not just ghosts that roam our streets trick or treating every Halloween. Vampires, werewolves and zombies are guaranteed to make an appearance. But could science explain some of our monster mythology? Katie Haylor spoke to infectious disease specialist Dr Bill Sullivan from Indiana University School of Medicine, asking firstly how a biologist becomes a monster expert...

Bill - I’ve been investigating infectious diseases for most of my career and I’ve been fascinated with how they induce behavioural changes in animals and people or the organisms they infect. These behavioural changes usually relate to how that pathogen transmits from one organism to the next.

Katie - This idea of infection seems to be one that crosses from biomedical to mythological I guess. Tell us about one of the most prolific or classic monster legends - this is the vampire.

Bill - Yes. The vampire legend originated in the 1600s. It’s a Slavic work for bloodsucker, and it originates from people believing that the undead need to continue feeding on blood in order to stay alive. There have been a number of infections that have been tied to vampirism. Rabies as you know causes aggression and it causes the infected individual to bite. There’s also a lot of foaming at the mouth because rabies causes  dramatic throat convulsions that makes it very painful to swallow. But the ties with vampirism is that vampires obviously bite to feed off the living.

There’s another interesting disease called porphyria, which is a blood disorder, in which case people have trouble making haemoglobin. Now that causes toxins to accumulate in the body; it causes the individual to look pale, they have red receding gums which kind of emphasise the fangs in their mouth (the canine teeth). And they also have a rather nasty skin condition where, if they are exposed to sunlight even for short periods of time, their skin will turn red and blister up very quickly just like in the vampire myth where vampires that are exposed to sunlight will start to melt away and die.

Katie - Gosh. Let’s move on then from one monster legend where rabies could be one of the origins to another. Tell us about werewolves?

Bill -  Oh yes. Rabies was once described as a disease that strips you of your humanity and leaves only the beast, which is precisely what you think about when you conjure up the idea of a werewolf. But there is also a genetic condition which could have, perhaps, fuelled the werewolf legend. It’s called CHL (Congenital hypertrichosis lanuginosa), and this produces excessive body hair, even hair that’ll grow on the forehead, the nose, the cheeks - it grows everywhere. Unfortunately, these individuals look very much like your stereotypical werewolf but, I hasten to add, there’s no behavioural changes that are associated with this condition. These people just have excess hair.

Katie - It’s really a case of mistaken identity, I guess, in the case of the werewolf legend. But one that really interests me is this idea, I guess kind of Victorian idea of reanimation, and this comes into play when we’re thinking about Frankenstein and Frankenstein's monster?

Bill - I think one of the key experiments was done by Galvani. He was the first person to realise, or discover, that electricity can animate the body. So what he was doing was experimenting on dead frog legs and he was dumping all sorts of chemicals and solutions onto this little frog’s dead leg and nothing ever did anything to it. But when he touched an electrode to it and put a little electricity next to those muscles, they started to quiver and shake and seemingly come back to life.

His nephew took this one step further and got fresh cadavers, criminals who were recently hanged, and put electrodes in pretty much every orifice that you can imagine. The cadaver, once it was charged with the electricity, would thrust out it’s hand; sometimes an eye would open; the body would shake a little. Of course, it wouldn’t come back to life, but you can imagine the people at the time and what they were thinking that no doubt helped inspire the story behind Frankenstein’s monster.

Katie - Frankenstein’s monster: it kind of correlates to the idea of the zombie legend in some ways, these creatures who are stumbling around and eating brains. Tell us a bit about the zombie legend.

Bill - Oh yes; that’s one of my favourites, and it gets back to some of the work that we do in my laboratory. The original zombies that stem out of Haitian religions are when a bocor, which is like, I guess, the equivalent of a priest, would zombify a victim by giving him or her a potion which actually contained paralytic agents. So they would often bury these individuals alive, and it’s been found that these toxins probably kept a person conscious, but he or she just couldn’t do or say anything about it. Then the bocor would go back a day or two later, dig the person up and, voila, they came back from the dead. The toxin had worn off and now they were very suggestive to whatever the bocor wanted to do.

That was the Haitian zombies, but there are a number of real world zombies that are basically parasites that are able to manipulate the brain, or the brain chemistry. Now a little closer to home is toxoplasma gondii: this is single cell parasite that can only complete the sexual stage of it’s life cycle in the belly of a cat, and we don’t understand the reasons for that. This parasite is well known to infiltrate the mammalian brain and, specifically in rodents (mice and rats), it changes their behaviour so that they are no longer afraid of cats and they tend to be easy prey. In other words, the parasite has altered the chemistry of the rodent brain so that it basically can get back into the cat where it can complete the sexual stage of it’s life cycle.