Zombies, à la the walking dead, don't exist in the real world, but they have been a big part of pop culture and show up time and again in history and folklore.

As portrayed in the classic 1968 film "Night of the Living Dead," zombies are lumbering, flesh-eating corpses. Some say this film reinvented zombies, who were shown in earlier films such as 1932's "White Zombie" as "beings whose brains had been zapped by some 'master' who was then able to control their actions," according to the University of Michigan website.

Zombies are even mentioned in Haitian folklore, with the Haitian word "zombi" meaning "spirit of the dead." These tales showed voodoo priests who had the ability to resurrect the deceased through the administration of a magic powder. And according to legend, "In Haiti a zombi is someone who has annoyed his or her family and community to the degree that they can no longer stand to live with this person. They respond by hiring a Bokor, a vodoun priest who practices black magic and sorcery, to turn them into a zombi," according to the Florida Museum of Natural History.

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Even the Centers for Disease Control and Prevention (CDC) has jumped on the zombie bandwagon, with a post on their website in May 2011 entitled "Preparedness 101: Zombie Apocalypse." The post, a tongue-in-check way to promote real disaster preparedness, went viral that week.

Of course, the CDC was not suggesting we need to worry about zombies. "If you're prepared for the zombie apocalypse, you're also prepared for hurricanes and flooding," said CDC spokesperson Dave Daigle at the time. Another scientific endeavor, by the Oxford Internet Institute, visualized in map form the global distribution of Google Maps references to "zombies."

While no scientific evidence suggests human zombies exist, there are plenty of zombies in the animal kingdom.

Recent research in a Thai rain forest showed how a parasitic fungi, a species of Ophiocordyceps, forces an infected ant to wander drunkenly over the forest's low leaves before clamping its jaws around the main vein on the underside of a leaf in an ant-zombie graveyard. [Mind Control: Gallery of Zombie Ants]

By watching 16 infected ants bite down, the researchers, who describe their findings in the journal BMC Ecology, found that the ants' last bites took place around Noon, indicating they are synchronized to either the sun or a related cue, like temperature or humidity. Another study found the fungus not only guided timing of death but also the zombie ant's whereabouts, on the undersides of leaves sprouting from the northwest side of plants that grow on the forest floor. That's where temperature, humidity and sunlight are ideal for the fungus to grow and reproduce and infect more ants.

Zombie caterpillars have also been spotted by scientists, with one study revealing the mastermind behind the gypsy moth caterpillar's zombie-like run for treetops once infected with a virus. Turns out, a single gene in the virus turns the caterpillars into tree-climbing zombies. Once up high in the trees, the caterpillars die and their bodies liquefy, raining deadly "zombie" virus onto their brothers and sisters below.

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