In the game and the series The last of us a zombie invasion is engulfing the world. These infected individuals are controlled by group fungi Cordyceps. The parasites really exist (although they are called Ophiocordyceps) and turn ants into zombie slaves. How do they do that and could they dominate people like this?
For example, the fungus Ophiocordyceps uses ants as puppets
If an ant contracts this fungus, you won’t see it at first, says assistant professor Charissa de Bekker of Utrecht University. She studies the interaction between the fungus Ophiocordyceps and ants. ‘Slowly the behavior changes, the ant no longer looks for food properly, communicates less with other ants and becomes hyperactive.’
After two to three weeks, the mold work really starts. Then the ant climbs up like a zombie and bites itself into, for example, a stick of moss. De Bekker: ‘The insect dies there, because the fungus eats the animal from the inside.’ After that, a stalk and a fruiting body grow from the ant. ‘That is the mushroom of this fungus,’ explains the biologist.
That mushroom releases spores, allowing the fungus to end up with new ants. For millions of years, fungi have used ants as a means of transport, food snack and nursery. A leaf fossil of more than forty million years old has even been found that contains the specific bite holes of such a zombie ant.
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Does the parasite just let its zombieized ant climb up anywhere? No: ‘There are signs that the animals choose a place where the fungus grows well, such as at a certain temperature, humidity and amount of light. ‘
How does the fungus control ants?
Controlling an ant as a puppet sounds complicated. How does the fungus pull the strings? ‘You might think that a fungus eats brain tissue and that this leads to behavioral changes,’ says De Bekker, ‘but that is not what we see. The cells of fungi do not penetrate the brain.’
What may enter the ant brain are substances that the fungus excretes. ‘We have indications that some of these proteins bind to areas in the brain where substances such as dopamine or serotonin normally bind’, says De Bekker. This could change the behavior of the ants.
And all those molecules are very interesting to De Bekker: ‘Perhaps we can use them to combat insects that attack our crops. Or do we find new medical applications for the substances. Antibiotics such as penicillin, for example, also come from fungi.’
The chance of human zombies is nil
Back to the zombies van The last of us. In the series, a large part of the world’s population is infected in no time because they ingest spores through food. According to De Bekker, this is not possible from an evolutionary point of view: ‘Something like that is absolutely not possible.’ The zombie behavior of the ants is the result of millions of years of changes in the fungus and the ants.
‘We think that the parasites were initially unable to change the behavior of their hosts, but that certain fungi had more offspring if they could interact better with their host and spread better through small adjustments. If this continues for millions of years, you will get very complex solutions for the spreading of traces,’ says De Bekker.
Such a process would also take millions of years in humans and fungi. Could there be zombies in the year 50,002,023? De Bekker: ‘No, the chance of fungi infecting us and changing our behavior in this way is really very small, our nervous system is much more complex than that of insects, we have a different immune system and this specific group of fungi does not like our body temperature.’
In short, you don’t have to fear a zombie pandemic caused by fungi even in the distant future.
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Human zombies will therefore not quickly arise via fungi. But just to be sure, you can test here how long you can live in a zombie apocalypse, should an invasion of brain chewers come to life in a different way.