The Last of Us - The Cordyceps Fungus

The developer Naughty Dog is imprinted on a generation of gamers, not least because their name blared out of our TVs every time we booted up Crash Bandicoot 3. They are the minds behind Crash, Jak and Daxter (one of my personal favourite game series of all time), and more recently, Nathan Drake of the Uncharted series.

Now, however, the studio are working on a brand new game, The Last of Us. Due to be release in May of next year, it's a post apocalyptic zombie story, only without the zombies. Naughty Dog have taken a genre that's considered a little tired, and given it an exciting new twist. Let's have a closer look.

The Set-Up:

You play as Joel, a black market dealer under the heel of the oppressive United States governmental regime. Two decades before the events of the game, a fungus known as cordyceps killed millions of people, resulting in the collapse of society. Those infected with the fungus today are inventively known as the Infected, and have giant fungal growths coming out of their bodies. The Infected are controlled by the fungus to spread spores as far as possible. It's not nice for anyone involved.

The Science:

Fortunately, cordyceps fungus is completely not a real thing, so there's nothing to fear.

Wait... What's that? OH DEAR GOD

Yes. It's true. The fungus that causes a mass extinction of humanity and a plague of not-zombies in a video game actually exists in the real world.

Wasn't that a scary sentence?

Luckily, fungi of the Cordyceps genus only infect insects, so we're safe for now. There's around 400 different identified species of the fungus, with each one infecting a different species of insect. It's actually a brilliant example of nature balancing out; if one species of insect becomes numerous, it is more likely to be infected and the numbers reduced.

So how does a Cordyceps fungi work? Free floating spores of the fungi will infect an insect by passing through its endoskeleton, using enzymes. It then infects the non-vital tissues and begins consuming them. The fungus spreads through the cells body, and then does something very clever.

In The Last Of Us, the Infected are controlled by the fungus to act in such a way that spreads more spores as far as possible. In the real world, the fungus does exactly the same thing. Whilst entomologists are unsure of the exact processes that takes place, the fungus most likely secretes specific chemicals that affect the insects brain function. This causes several things to happen.

Firstly, the insect will have convulsions. This makes it fall from whatever branch or leaf it might be on. Next, the insect is forced to climb to a select height on a plant, which varies between different cordyceps species. Then the insect will bite down excessively hard into the leaf it is on, and anchor itself in place. At this point, the fungus finally kills the insect, and moves into its fruiting stage. As you saw in the video, the fruiting body of the fungus erupts out the head of the unfortunate victim, ready to release more spores to infect more insects.

The reason for this mind control exercise is that it gets the insect into the optimal position for the fungus to fruit. Cordyceps often require a specific temperature and humidity to fruit, so they use the insects as their unwilling vehicles to achieve that.

The control that Cordyceps exerts over the insects it infects is quite astounding. In fact, ants that have been infected are often referred to as "Zombie Ants" because of their behaviour. 

It seems then that Naughty Dog have actually got the science pretty spot on with The Last of Us, even if Cordyceps doesn't infect humans. As you can see in the picture below, the fungus even fruits out of the top of the Infected's heads...

...which is actually really gross.