© Getty Images

What are zombies? -

As you probably know, the more common understanding of zombies is that they are creatures reanimated from dead corpses that lack the inherent consciousness, intelligence, and free will that we attribute to humanity.

© Shutterstock

History -

Zombies as we know them have very largely been the product of science fiction and fantasy. The 'Epic of Gilgamesh,' a poem from ancient Mesopotamia, is one of the oldest references to zombies, dating to the 7th century BCE.

© Public Domain

Biological plausibility -

While it is accepted that zombie infections as portrayed in the media are fictional, some aspects of zombies could theoretically arise from real-world phenomena. Let’s take a look at them now.

© Getty Images

Pathogens -

Certain viruses or parasites could cause symptoms resembling zombie behavior by affecting a person’s cognitive function or inducing aggressive behavior.

© Getty Images

Siberia zombie virus -

In 2022, a team of European scientists revived a 48,500-year-old 'zombie' virus that was retrieved from the permafrost in Siberia. Although the internet was aflame with fear about a potential outbreak, you can rest assured that the virus is no threat to humans and it can only infect amoeba.

© Shutterstock

Mutation -

There is also the theory that an existing pathogen could mutate and potentially lead to a contagious condition that alters human behavior.

© Shutterstock

Neurological disorders -

Diseases affecting the brain could induce zombie-like symptoms, though not to the extent of an apocalypse. An existing brain disease known as kuru is the closest humans have come to a zombie outbreak; it creates simple mood changes and an inability to speak. But if you don’t eat human brains, then you don’t have to worry, since that’s how it spreads!

© Getty Images

Neurotoxins -

Certain toxins, such as snake venom and human-made chemicals, could induce zombie-like symptoms. But widespread exposure is incredibly unlikely.

© Getty Images

Zoonotic diseases -

Another way that humans could potentially fall to widespread illness is through zoonotic diseases, which are transmitted from animals to humans. But while this could lead to catastrophic effects in civilization, these diseases would not take control of humans like you see in zombie films.

© Getty Images

Psychological phenomena -

Mass hysteria or even psychological disorders could lead to behaviors that are reminiscent of a zombie outbreak from movies, though not in the literal sense.

© Shutterstock

Environmental factors -

Environmental changes or disasters could create conditions that are conducive to a breakdown of society. This could potentially resemble an apocalypse, but not in the way that corpses are reanimated into undead creatures.

© Getty Images

Cordyceps -

In the video game and series 'The Last of Us,' a zombie outbreak is caused by a fungus known as Cordyceps. While this fungus does exist in the real world, its ability to overpower a host is limited only to insects, seeing as most fungi cannot thrive in our relatively high body temperatures.

© Getty Images

Climate change -

Environmental changes could lead to shifts in existing diseases. As the Earth warms, there may be viruses and fungi that adapt to increased temperatures, and so they might thrive in the human body. But scientists believe that, whatever happens, humans wouldn’t be infected to the extent of resembling zombies.

© Shutterstock

Biological warfare -

Theoretically, biological weapons could be engineered to induce zombie-like symptoms in humans, but this remains highly speculative and no proof has been provided that such weapons could ever exist.

© Shutterstock

Genetic engineering -

Advances in genetic engineering could theoretically create organisms with zombie-like traits, but ethical concerns and global treaties make this scenario highly unlikely.

© Shutterstock

Societal collapse -

While this doesn’t exactly fall into the realm of zombies, societal collapse due to various factors could create conditions similar to those depicted in zombie fiction. In fact, this is the primary theme that tends to be used in literature and the media when it comes to apocalyptic stories.

© Getty Images

Technological dependency -

Overreliance on technology could make society vulnerable to widespread disruption, but this once again touches on an apocalypse that doesn’t really take over actual human consciousness.

© Getty Images

Cyber threats -

Cyber attacks on critical infrastructure could disrupt society, but this would be very far from creating zombies. Cyber security around the world is constantly taking strides to address potential concerns that could destabilize society.

© Shutterstock

Technological threats -

Rogue artificial intelligence or technology gone awry could also potentially cause widespread chaos that resembles a zombie outbreak. Some tech companies, such as Elon Musk’s Neuralink, have even been attempting to create neural implants, causing people to question whether such technology can control brain activity.

© Shutterstock

Resource scarcity -

Competition over dwindling resources could lead to violent or erratic behavior reminiscent of an apocalyptic event. But we’re quite certain that this would not be in a zombie-like manner.

© Getty Images

Pandemics -

While pandemics are a real threat, they typically don't result in the rapid reanimation of the dead as depicted in zombie lore. Indeed, modern science has increasingly limited the spread of diseases, which means that global pandemics are rare (but clearly not impossible).

© Getty Images

Social decay -

If social structures were to hypothetically deteriorate for whatever reason, then we would most likely see society become lawless and violent, akin to some aspects of zombie fiction.

© Getty Images

Military experiments -

Some speculative scenarios involve military experimentation gone wrong, which could theoretically result in a zombie-like outbreak. After all, many real-life experiments have been conducted on people in the past, especially by military entities.

© Getty Images

Environmental contamination -

Although this is very readily a theme of science fiction, water supplies and agriculture could be contaminated by hazardous chemical spills, radiation leaks, or other environmental catastrophes. Humans would be exposed to the toxic substance, and their physiology would theoretically turn into a zombie-like state.

© Shutterstock

Psychotropic warfare -

A psychotropic drug or a mind-altering substance could induce hallucinations and violent behavior in susceptible individuals. Such an outbreak would spread rapidly as people succumb to the effects of the substance or collective hysteria.

© Getty Images

Supernatural -

Although this is entirely speculative and heavily fictional, there is the theory that supernatural or paranormal forces could reanimate the dead and create an outbreak that defies scientific explanation.

© Shutterstock

Unintended consequences -

Human actions have been known to have adverse effects on the environment, and this could be no different. Unforeseen consequences could arise from humanity that cause an outbreak like this, but it is incredibly speculative.

© Shutterstock

Preparedness -

Even though a zombie apocalypse itself is highly unlikely, the idea has prompted many global discussions about disaster preparedness, particularly regarding contagious diseases and unknown pathogens.

Sources: (National Geographic) (New York Post) (Daily Nexus) (National Center for Biotechnology Information) (Newsweek)

See also: What is zombie deer disease?

© Getty Images