For some reason, the concept of zombies — the living dead, the undead or whatever you’d like to call them — fascinates humanity.

The attraction has garnered a considerable boost in the past 10 years or so with the popularity of shows like The Walking Dead and movies like Zombieland, Shaun of the Dead, Warm Bodies and 28 Days Later.

READ MORE: ‘The Walking Dead’ Season 6 finale may be the last straw for fans

Down deep, most of us know that there’s no such thing as zombies — or is there?

Zombies 101

First, let’s take a look at how the idea of zombies began.

Zombies first came to life in Haiti during the 17th and 18th centuries. Hundreds of slaves were taken from Africa and transported to Saint-Dominque (present-day Haiti) which was ruled by the French. Deaths among the slaves were high. Initially, it was believed that once slaves died, they would be freed from slavery and return back to Africa. But throughout time, the legends evolved into the practice of voodoo — specifically bokor — with Haitians believing that the undead were bewitched to perform evil tasks.

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And the word zombie is thought to derive from the Kongo word nzambi, meaning “spirit of a dead person.”

For the most part, stories about the undead were relegated to Haiti, but soon evolved into pop culture with the first film White Zombie (1932) and eventually the cult classic Night of the Living Dead. And it just became more popular.

Real-life zombies

Okay, down to the nitty-gritty: how could a dead body function?

If you’re a fan of The Walking Dead, you might remember that the “walkers” (zombies) were a result of neurons firing in the brain, reanimating the body and leaving not much else functioning, aside from the requirement to eat.

But could a person wander around with a shuffling gait, catatonic, focused on solely one thing: food?

Believe it or not, yes.

WATCH: Rick And Noah Escape ‘The Walking Dead’ Zombies

But nobody said a dead body could. However, there are several diseases that leave its victims with zombie-like traits.

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Take Klüver–Bucy syndrome. According to Peter Cummings, a neuropathologist at Boston University and an advisor to the Zombie Research Society (yes, there is such a thing), if one took a look at someone afflicted with this disease, it might make you think the zombie apocalypse is nigh.

“That has a whole bunch of weird stuff,” Cummings said of the syndrome. “There’s hyperorality [the desire to put inappropriate objects in your mouth], the inability to recognize objects, distractibility and dementia … in their catatonic state, they can become quite violent.”

Cummings explained that the problem lies with the amygdala, the part of the brain that is responsible for survival instincts, emotions and memory. He explained it like this:

“If I spilled coffee on you, you might want to punch me in the face. That’s due to the limbic system. But usually the frontal lobe shuts that response down,” he said. “But if you lose that connection, the amygala takes over and that response takes over.”

There’s another disease called encephalitis lethargica, an extremely rare condition. Cummings said that there was an outbreak connected with the Spanish Flu epidemic of 1918. People who suffered from this began to hallucinate, entered a stupor and became catatonic. However, if they were stimulated — with something as benign as a tap on the shoulder — they “went beserk,” said Cummings who has also written The Neuropathology of Zombies.

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. As well, they had shuffling gaits and even motor defects.

“Now, doesn’t that sound like a zombie?” said Cummings. Tweet This

Okay, so Cummings doesn’t exactly believe in zombies, but as he’s illustrated, people who are ill can enter zombie-like states that render them almost lifeless.

In the case of encephalitis lethargica, it sounds like the “rage virus” in 28 Days Later.

“There are real things out there that effect the brain to alter behaviour where you do socially unacceptable things,” he said.

Maybe chow down on someone’s arm?

WATCH: Diagnosing a zombie: Brain and body

Zombies in nature

Okay, so maybe you’re not convinced human zombies could possibly exist. But there are many examples of zombies in the natural world.

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There is a fungus from the genus Ophiocordyceps that, unbeknownst to the insect victim, invades its body, spreading, eventually taking over the host within days. This fungus essentially controls the body, forcing it to climb up high, when — straight out of Alien — it bursts out of the victim’s head and falls down below to carry on the cycle.

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This type of parasite has been around for millions of years, through various forms.

One such Ophiocordyceps fungus also makes the Camponotus leonardi travel along the grounds of the rainforests of Thailand where it clamps down on the underside of a leaf, protecting the fungus where it is allowed to thrive.

WATCH: Zombie ants

What to do in case of zombie apocalypse

So there’s probably not going to be an actual zombie apocalypse. But there could be something that could see the world come to a standstill, such as a viral pandemic or a major solar flare that disrupts communication and other necessities of the western world.

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And perhaps it’s the fear of such things that has lent itself to the zombie obsession.

The 2003 blackout of the northeast including Ontario and Quebec that left some 55 million people in the dark made people realize just how much they could be left disconnected and unprepared for any large-scale issue.

“Zombies have two things that touch on us, and I think one of those is we’re afraid of a viral pandemic, but we’re also afraid of each other,” Cummings said. That might explain the mostly human-on-human violence in both the comic book and television incarnations of The Walking Dead.

Now, if you’re worried about a potential zombie apocalypse, who better to prepare you than the U.S. Centers for Disease Control and Prevention. Here are their tips to making sure you survive the undead. Or maybe just a widespread blackout.

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