Short Wave - The Zombies That Walk Among Us

Episode Date: October 31, 2019

The idea of human zombies probably seems pretty far-fetched. But there are real zombies out there in the animal kingdom. Ed Yong of The Atlantic creeps us out with a couple of examples. Hint: they involve fungus. Follow Maddie on Twitter - she's @maddie_sofia. Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Dorby. Happy Halloween, everybody. Get excited because today we are getting creepy, we're getting crawly, and we're talking zombies. Humans have been fixated on zombies for a long time. There's the Night of the Living Dead, the Walking Dead. You know about the dead people, right?

The walkers. Now, clearly we've never had a big zombie human situation. But there are zombies in the animal kingdom. For example, zombie fungus, a parasite that takes over the bodies of insects to do their bidding. Which is why we brought in Ed Yong, science reporter at the Atlantic and Halloween superfan. What's your favorite Halloween candy? I don't have any. What?

I don't do Halloween. I'm British. We hate fun. Ed's written all about the fungus that walk among us. I'm Maddie Safaya. So today? We're going to talk about parasites that take over and control the brains of their hosts. Yes. Much like a podcaster does to their audience. Okay, so we're here with Ed Yong.

He's here to talk to us about parasitic zombie fungus. All of these cases of parasites that manipulate their hosts are really about the parasites turning the animals into vehicles when making more parasites. All right, Ed, first up. You want to go cicadas? Mm-hmm. Let's do cicadas.

All right. Paint me the picture of where the zombie story starts for the cicada. Right. So cicadas spend most of their young lives underground feeding on roots, and they emerge en masse, flying around, trying to find mates, making a lot of noise. Sometimes when those cicadas emerge after 13 years feeding on roots, they'll encounter the spores of a fungus called massospora, which will grow into them and through their bodies,

sucking up all the juicy cicada nutrients that are there. And then they will make the cicadas fall off. So the bottom third of the cicada just slops off. And in its place is this ball of white fungal spores. And so the cicadas are now flying around, trying to find mate, hyperactive, really. releasing clouds of spores as they go. Matt Casson, who studies them, calls them flying salt shakers of death.

It's a great band name. Right, right. I saw them at Coachella, I think. So what about the fungus makes them do this? Okay, so Casson found that the spores are releasing a bunch of different chemicals. And one of them, to his incredible surprise, is psilocybin. Like psilocybin of the shrooms variety? Exactly that.

The hallucinogen that makes people trip when they take shrooms. So the cicadas are that running through their system. Who knows whether they're tripping or not? They also have another, the fungus is also producing a thing called kathionine, which is a type of amphetamine. And that probably explains why the cicadas are so hyperactive. And the goal of this for the fungus is to spread its spores. Right, yeah.

Okay, so cicadas aren't the only things being infected by a mind-controlling fungus, right? Like ants are very famously also getting it from the fungus. Yeah. Many ants are infected by a fungus called Ophia cordyceps unilateralis, or just cordyceps for short. This is a really famous example. It's been documented in things like planet Earth. So there a fungal spore will land on an ant and borrow into the ant and start growing throughout. So these fungal threads.

will invade the ant's bodies, they will insinuate themselves between the ant's muscles and start to take over. As a result, the ant crawls away from its nest, up a plant stem, and then when it hits a very specific height, like 25 centimetres, it goes onto a leaf,

grips the underside of the leaf with its jaws, and just stays there. And that's all it will now do. So the fungus is taking over its body, severs the muscles controlling the mandibles, so the ant is now locked into place on this leaf. And then the fungus sends a tube growing through the ant's head. And the ant is usually on the underside of the leaf now. Right.

So it falls like onto its colony. Right. Right? Exactly. Yeah. So those spores then rain down onto other ants that are walking beneath this one. It's like the fungus has turned the ant into some kind of zombie sniper for taking it. out other ants. Do we know how the fungus does this? Right. So unlike with the cicadas,

the chemicals that are going on here aren't so clear. People like David Hughes have done microscopy experiments looking at the fungus inside the ant. And we see that the fungus seems to destroy a lot of the neurons connecting the ant's brain to the rest of the body. And it also grows around the muscle cells. So here's a guess. It seems like the fungus, is cutting the ant's body off from the brain and just taking over. So maybe Hughes thinks it acts like an actual puppet master. Right. I think one of my favorite things about this fungus is it doesn't actually get into the brain, right?

Right. So that's like you would think like brain, mind control, the fungus is up in the brain. No. For sure. Yeah. Like I think one of the most amazing things about these parasites is that they achieve so much precision and such incredible control of their hosts, and they are really simple. Okay, so these are just some examples, but these are really common,

like maybe unsettlingly more common than people think. Right, yeah. So I think a lot of people think of parasites as this very niche lifestyle, that they're these obscure things that maybe are doing their weird, gruesome stuff, often some corner of the world, and we don't need to think about them very much. but they are actually one of the most prevalent lifestyles around. And the animals that are parasites are a critical part of the world around us. So, for example, a lot of the parasitic wasps control the populations of other insects.

And so do the cordyceps fungi that we talked about. So if you didn't have those, maybe populations of things like pests would run out of control. So they may be, you know, let's not just say write them off as bad. Right. I mean, they're definitely grisly, a bit gruesome, but they are as much as a part of the circle of life as anything else. So, you know, you've spent a lot of time reporting on this. Where do you think this obsession that we have with zombies comes from? Because humans are extremely into zombies and this idea of mind control.

I think with zombies, it's the fear of death. Like, zombies are the specter of our own mortality slowly. creeping up on us. But the thing about parasites is that it fuses that fear with the fear of having our own minds controlled. I think the idea that it might be the work of another organism, especially another organism that you can't see is terrifying. And, you know, it's not a coincidence, I think, that a lot of these parasites belong to groups of organisms. organisms that don't have the best reputation. So things like wasps, bacteria, and fungi.

The fact that it's those particular things, I think, adds another layer of unsettling horror to it. Well, Ed, thank you for coming by, Ed. Say goodbye to the audience, Ed. Goodbye. Okay, before you go, heads up. Tomorrow we extend Halloween for one more day. to answer a scary listener question. See you then.

And do you see how I mind controlled you there? Did you see, did you notice? I did. It was pretty subtle. I thought I would let you.