Zombies are real – not in the walking dead sense, but there are parasites that can hack the brains of living creatures and force them to do things against their will, with the goal of spreading the infection. That relative realism is why The Last of Us hits so hard, and the launch of the second season feels like a great time to explore some of the real-world zombie stories that inspired it.
The modern zombie legend started with George Romero’s original Night of the Living Dead, where the recently deceased just wake up with a new hunger for human flesh. The Walking Dead franchise continued the idea, where dying from any cause gets you a one-way ticket to zombiedom. Neither really bothered explaining the science behind it, and they didn’t really need to.
Later zombie stories tried to frame the condition as a virus, usually created in a lab so the writers can cram some allegories for greed and pride in there. That virus could work like rabies and trigger an uncontrollable rage in infected people, like in 28 Days Later, or mutate people and animals into monstrous creatures like in Resident Evil.
But The Last of Us gave the apocalypse a natural cause, one that’s chillingly plausible. The Cordyceps fungus is not only real, but it actually turns its hosts into functional zombies to help it spread to new victims. In the fiction of the show (and the games it’s based on), all it took was one strain to evolve to jump from infecting insects to animals and finally to humans. That’s a similar route that illnesses like bird flu and COVID-19 have taken.
Here’s the horror story of its real-life counterpart.
The fungus that hijacks ants like a ghastly marionette
The humble carpenter ant is the unsuspecting victim of this nightmare. They normally live in forest canopies, but occasionally have to venture down to the ground – and that’s where the parasite strikes.
Ophiocordyceps unilateralis spores attach to the exoskeleton of the ants, eventually digging their way into the nervous system. As the fungus takes hold, the ant begins to convulse, shaking it from its canopy nest back down to the ground. Soon the bug loses control of its body completely, although its brain stays intact and uninfected, suggesting that whatever consciousness an ant has would be preserved.
The parasite basically forms its own nervous system of fungal cells, which allow it to control the ants’ muscles like a puppet. The infected ant is forced to climb the stem of a plant to the underside of a leaf, then clamp its mandibles onto the leaf vein so tight it can never unclench.
Only then does the fungus finish the job, killing the ant and consuming it from the inside for sustenance as the parasite grows. Over a few days, a stalk bursts out of the ant’s head, and eventually pops open to release new spores down to the unsuspecting ants milling around on the ground below. And the nightmarish cycle begins anew.
The flatworm that found a zombie on/off switch
Other parasites have taken more careful control of their hosts, switching zombie states on and off like a light switch.
The lancet liver fluke lives its adult life inside sheep or cows, but it doesn’t just pass its home onto its offspring for free – no, those kids have to earn it through a seriously convoluted path back to their homeland.
After the fluke mates, its eggs are pooped out by the host. If they want a chance of hatching, they have to wait until they’re eaten by a passing snail. Inside this first host, they develop into larval parasites, until the snail gets wise and ditches the freeloaders in slime balls.
Along comes host number two, an ant, who definitely gets the raw deal. After it slurps the moisture out of the infected snail slime, the parasites hole up in its gut, except for one – this martyr heads to a cluster of nerves near the ant’s neck and drives it like a horse and cart.
In a similar story to the fungus, the flatworm forces the ant to climb a stalk of grass and sit at the top, just waiting for a cow or sheep to come along and eat the grass, getting the parasite back to its chosen breeding ground.
But here’s the kicker: the fluke knows that leaving the ant out in the blazing sun all day would kill both host and parasite, so it only drives up there to watch the sunset. If nothing eats it by morning, the worm lets go of the reins. The ant snaps out of its fugue state and wanders home, probably confused and unable to explain to its colony-mates where it’s been all night.
When darkness falls though, the parasite takes control once again, like some tiny werewolf night after night, until the hapless ant finally gets eaten. The driver fluke dies along with the host, but all those taking shelter in the ant’s gut finally get to their ancestral home in the sheep or cow.
But they don’t learn from their tough upbringing, and go easy on their own kids – no, they repeat the pattern and go on to kick them out to find their own way in the world.
The wasp that uses zombie-spider labor to build its home
Other parasites use zombies to build a better life for their family. Spiders are famously handy home-builders, so Polysphincta wasps employ their services – against their will.
It starts off with an adult wasp paralyzing an orb-weaving spider and laying an egg on its back. When it hatches, the larva will bite into its gracious host and start snacking on the fluids inside – but it doesn’t kill the spider straight away.
The wasp larva starts to control the spider’s behavior, coaxing it to build a different type of web. Instead of the big, wide, insect-catching kind that it usually makes, the host will roll a little cocoon. When it’s done, the larva thanks the spider for its hard work by eating it, then curling up cosily in its new home while it grows into an adult wasp.
Studies suggest that the wasp larva hacks its host by injecting hormones that tell the spider it’s time to molt. The cocoon web does look suspiciously like the type the spiders use to protect themselves during that vulnerable molting period.
If you’re reading this, Hollywood, there’s a fun twist on the zombie trope here: imagine a world where infected humans start building houses for the zombies.
The tapeworm that makes ants lazy and coddled
This parasite functions like a real-life version of The Substance, granting eternal youth and making those around you want to wait on you hand and foot – and of course, there’s a dark downside.
The players in this piece are again ants and tapeworms. Worker ants of the species Temnothorax nylanderi normally live for a few weeks or months at most, but when they’re infected by the tapeworm Anomotaenia brevis that extends several years. They might even live as long as queens, who often reach 20 years.
They not only get the lifespan of a queen, but all the social benefits too. Uninfected workers feed, groom and even carry around infected ants, who get to just sit around all day and not chip in with any of the usual tasks.
Closer inspection shows that the tapeworms switch on certain genes in their ant hosts that “promote” them to queens, and the chemical signals they give off inspire other workers to want to look after them.
It sounds pretty sweet for the infected ants, but there’s always a catch. With multiple so-called queens to look after, the workers become more stressed and die younger than they normally would, meaning the colony as a whole suffers.
And what’s in it for the worms? It turns out that they’re playing the long game, and it’s all a ruse to get them back to their preferred breeding ground – the guts of woodpeckers. By making their host ants coddled and lazy, they won’t be able to flee like their uninfected colony-mates when a woodpecker comes knocking on the nest.
We’ll let Disney and Dreamworks fight it out over whether this story becomes a sequel to A Bug’s Life or Antz.
