Hey, Thoughty2 here.
One of the greatest myths of childhood is that when we grow up, we’ll finally be in charge.
But while it’s true that reaching adulthood means you get to choose our own bedtime and
eat pizza for dinner every night, the idea that we suddenly become masters of our own
destinies is simply an illusion - whether it’s paying taxes or staying at home during lockdown,
sometimes we all have to do things we don’t want to do. Still, aside from the rules and
regulations passed down by the government, our employers, (...and our partners),
we like to believe that our decisions are ours - and ours alone - to make.
But even that’s far from a sure thing - philosophers and thinkers have been
debating whether or not we truly have free will ever since some guy in a toga
first wondered why on earth he drank that third flagon of wine last night.
Don’t worry, I’m not going to open that philosophical can of worms here - I have
another whole video dedicated to the topic of free will - but suffice to say humans are quite
attached to the notion of being autonomous beings that get to choose their path in life,
and it’s not hard to see why. To believe the opposite is to accept that our futures have
already been laid out before us, and that we’re mere NPCs rather than active players.
You might even say we’d be no better than zombies, which would actually be quite
handy because then I could casually segue into the topic of today’s video, real-life zombies.
Now, if you’re going to be a scientific wet blanket and declare that there are no such
things as zombies, I suggest you visit Ikea on a Saturday afternoon and see for yourself.
Pay close attention to the faces of men aimlessly pushing trolleys, nodding and smiling when asked
whether they prefer the SKOGSKORN scatter cushion or the TUVSÄV. Notice the emptiness in their eyes,
their vacant expressions, and the way they follow the arrows of flatpack doom as if slaves to some
unseen force. Admittedly that force is probably the promise of Swedish meatballs and a slice of
Daim cake rather than the chance to feast on the brains of the living, but still.
Of course, it isn’t just really big Scandinavian furniture shops that have the power to turn
living beings into mindless zombies - that utter sadist Mother Nature is pretty good
at it too. Because real life zombies are surprisingly common in the natural world.
Take, for example, Plesiometa argyra.
This poor spider is routinely chosen to play an unwitting and unhappy support role raising the
young of a certain parasitic wasp who’s breeding habits read like something out of a horror film.
The wasp starts by paralysing the spider with a single sting before laying her larvae
on the surface of its body. Along with the unwanted babysitting gig,
the spider receives another sinister surprise - brand-new biological coding.
The wasp’s larvae begin to grow, sucking on the spider’s bodily fluids through tiny puncture
holes they make in its abdomen. To begin with, the spider basically just goes about its regular
spidery business as if a host of tiny parasites aren’t making milkshake out of its insides.
But after two weeks, something changes. Through a mechanism we still don’t understand,
the spider will suddenly stop tending to its large circular web,
and will instead feel compelled to craft a small, sturdy platform unlike any web it’s
ever woven. The spider will spend the last night of its life on this crazed construction project,
and its reward for finishing is to be eaten alive by the hungry larvae hanging out on its abdomen.
With that final nutritious meal in their bellies, the larvae will begin spinning
their cocoons, which they neatly hang from their bespoke spiderweb scaffold.
Another real-life zombie is the woodlouse, also known as the pill bug, a common household critter
with a fatal fetish for faeces. This little poo nibbler has a particular thing for bird droppings,
including those deposited by starlings. Unfortunately for the pill bug, starling
digestive tracts often carry a parasite that’s far more dangerous to the bug than it is to the bird.
Once safely ensconced inside the pill bug, the parasite seizes control. To complete its life
cycle, it needs to make its way back inside a starling, and so it compels the woodlouse to seek
out the most exposed location it can find. Nothing is as tantalising to starling tastebuds as a pill
bug out in the open dancing the macarena, so the insect is soon gobbled up, and the parasite goes
back to colonising the gut of its original host. Clever. Disgusting and horrifying, but clever.
The green-banded broodsac, uses similar poo-based tactics, only this time it’s a species of snail
that eats the bird’s faeces. It’s well known that snails are absolutely terrible at the macarena,
so the broodsac has another way of attracting the interest of the local bird population - it
grows directly into the snail’s eyestalks, where it begins to throb and pulsate,
doing a surprisingly good impression of a catapilar. Before you can say ‘Simple
Simon,’ in swoops a bird to gobble up the snail… and the broodsac along with it.
As horrific as all these examples are, nothing strikes as much undead fear as fungi.
The natural world is made up of multiple kingdoms, with the most well-known being Plants,
Animals and Narnia. Fungi, which include yeasts, moulds, and mushrooms, have a kingdom all to
themselves and judging by the name, it’s where you want to go to have a good time.
There are, of course, many different types of fungi that do many different things,
including entomopathogenic fungi, that infect (and often kill) insects.
One such fungus is Beauveria bassiana that can be found growing in soils all over the
world. It infects insects and other arthropods by penetrating their exoskeletons and growing inside
them, killing them within a few days. If that was all this fatal fungus did I’d consider it to be
pretty bloody rude, but no. Beauveria bassiana then proceeds to colonise the poor insect’s
corpse, its spores appearing all over the dead body before drifting off into the air in search
of more stuff to murder. Beauveria bassiana is so good at wiping out certain types of insects
it’s actually used as a biological insecticide to control bugs like termites, aphids, and beetles.
It’s safe to say Beauveria bassiana behaves brutally, but as far as Entomopathogenic fungi
go it’s arguably one of the friendlier ones. A particular genus of fungi known
as cordyceps found worldwide in tropical and temperate regions has a very particular skill:
it doesn’t just kill its hosts, it first releases chemicals into their brains, taking control of
their bodies and turning them into automatons. No wonder it’s known as ‘zombie fungi’. No one
knows exactly how many cordyceps species there are, but there are at least 600, and most target
a single species of insect - anything from butterflies to dragonflies and cockroaches.
Ophiocordyceps curculionum attacks weevils in Central and South America. Ophiocordyceps sinensis
kills caterpillars up in the Himalayas. And ophiocordyceps humbertii infects wasps in Brazil,
causing them to land on a leaf or branch and bite down into it before passing away.
This peculiar behaviour is also seen in the effects of the ophiocordyceps unilateralis,
probably the most famous of the cordyceps fungi and scourge of ants across the globe.
Like its fellow zombie fungi, unilateralis gets inside its victim using special enzymes
that dissolve chitin, the fibrous substance that makes up most arthropod exoskeletons.
Once inside, the fungus takes control of the ant’s brain, making it climb high into a tree
where it bites down on a leaf and pops its six tiny clogs. Soon, the fungus begins to bloom,
growing out through the ant’s exoskeleton into balls of spores that burst and shower down on
all the ants scurrying across the forest floor below, starting the process all over again.
It’s a terrifying mode of operation, but it’s also very successful,
because cordyceps have been playing this game for a very very long time. Fossil records show zombie
ants controlled by cordyceps-like fungus were taking their last bite into a leaf at least 48
million years ago. Other researchers have found a fungus-infected insect stuck in amber that
goes back more than 100 million years. Part of the reason for this success is fungi’s adaptability.
Scientists recently discovered that ants are sometimes colonised by more than one species of
cordyceps. Originally it looked like the two different parasites were living in harmony,
but further research suggests that this is probably an example of hyperparasitism,
a situation in which one parasite becomes infected by another. Remember I said earlier that fungi eat
into insect’s bodies by dissolving the chitin in their exoskeletons? Well, guess what also
contains plenty of chitin? Fungi! So, in another weird turn, fungi are practically designed to
infect each other, which is why some cordyceps cannibals specialise in attacking other cordyceps.
So, we’re talking about a hyper-adaptable organism that can colonise something thousands
of times bigger than it, taking over its mind and forcing it into some form of ritualistic suicide.
By now there should only be one question on your mind…
but don’t worry, there’s no reason to believe humans can be infected by an as
yet undiscovered fungus and turned into real life Clickers from The Last of Us.
In fact, it’s kind of the opposite - we may be able to use these fatal fungi to our advantage.
Cordyceps fungi contain a chemical called cordycepin that, in biological organisms,
switches on a cellular protein called AMPK. And it turns out AMPK is pretty powerful stuff.
Initial tests suggest drugs that trigger AMPK production in our bodies are able to reverse
some types of diabetes and cancer, limit heart disease, and even make us live longer.
Now scientists think they’ve found a way to grow cordyceps fungi effectively in laboratories,
potentially opening up the way for new anti-viral and cancer-fighting wonder
drugs based on cordycepin. Of course, it might be a hard pill to swallow when you know the
medicine you’re taking is made from a zombie fungus. Then again, maybe it’ll grow on you.
Thanks for watching.