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Monday, 7 September 2020

Zombies in nature

Haitian folklore tells of the zombie: a reanimated corpse. In modern day, the zombie is portrayed as parasitic, feeding on the brains of others and so infecting them
Zombie via Wikipedia Commons.
to become zombies too.

There are various parallels in nature: fungi that infect the brains of ants, the Euhaplorchis californiensis worm that infects fish, or the toxoplasma gondii parasite that infects rats (there’s more about toxoplasmosis here) – all these force their hosts to change their behaviour to help spread the fungal spores, or get themselves eaten by a bird or cat, where they can reproduce.

We don’t know how this happens, but researchers looking at some of these parasites found they excrete chemicals that alter brain chemistry. In their target host, the cocktail has a profound affect on behaviour, but doesn’t work so well in other species.

These’ve all been dubbed zombie hosts, and you can see the similarity to the modern interpretation. But this interpretation is changing – zombie, like vampires, are becoming warmer and fuzzier – and there’s an important factor missing when compared to the original, Haitian zombies: the hosts aren’t dead.

One of my novels features the execution and revival of criminals, whose brains are then studied. The longer since death, the more changes, and the more irreparable – which does make you wonder how Victor Frankenstein repaired the bodyparts he harvested. But was Frankenstein’s monster a zombie? In the days of modern medicine, isn’t anyone who’s been resuscitated or had a near death experience a zombie, then, by the same rules? At what stage does “alive again” become “reawakened from dead”?

Often, the parasite ends up killing the host, but not always, and this certainly isn’t the aim. Like the horsehair worm, which reproduces in water, and so inspires its insect hosts to dive – frequently with fatal consequences.

But seemingly suicidal behaviour isn’t even unheard of in the animal kingdom outside of parasites. The male fairy wren mysteriously mimics the call of the butcher bird that preys on it when females are nearby (and only males do this). Scientists think it may be to show bravado. However, it catches the butcher birds’ attention as well as the female fairy wrens, and results in high mortality. So I guess if passing on death is zombie-like, there’s a gene somewhere that has much to answer for.

To read more about birds, check out our article

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