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Why would zombies eat humans and not any other animals? Are there any chemicals or vitamins that can only be found in human bodies and not other animals?

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closed as too broad by A Lambent Eye, Cumehtar, AndreiROM, JBH, Measure of despare. Jun 24 at 16:32

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    $\begingroup$ Do whatever you want, but I just want to point out that if you write fiction about zombies, please consider spending more thought on what zombies are. Doing hard science zombies is, well, unless you are a scientist, you can't pull that off. They've always been a metaphor for the dangers society is facing, from turning away from christianity in the middle ages to communism, consumerism, terrorism ... cats won't become consumed by communism. $\endgroup$ – Raditz_35 Jun 23 at 11:33
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    $\begingroup$ Zombies eat human braaaaaains simply because they are exceptionally yummy. And part of this complete breakfast. $\endgroup$ – user535733 Jun 23 at 13:44
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    $\begingroup$ @Raditz_35 you mean I've spent the last 40 years protecting my cats against the Red Scourge for nothing? Where's McCarthy when you need him? $\endgroup$ – JBH Jun 23 at 17:15
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    $\begingroup$ I remember for sure they were eating mice in "Something something of the Dead". Also pigs in one episode of "The Walking Dead". If, however, I would want to invent a reason for my zombies to eat humans exclusively, I would say they retain some vestiges of social instincts, yet their "social interaction" is now limited to eating. $\endgroup$ – Headcrab Jun 24 at 5:53
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    $\begingroup$ In the original, Night of the Living Dead, they ate anything that moved. There's a shot of a zombie eating a lizard at one point. It's not uncommon in zombie lore for the dead to eat animals (see Rick's horse in the Walking Dead). Non-domesticated animals wouldn't have much trouble avoiding the dead (smell, speed) and domesticated animals would fall prey quickly. Humans are different. They're wiley, so they survive longer, they're slow, so are vulnerable, and are not too hard to discover, and are numerous. That's how they end up being the most common prey. $\endgroup$ – Will Jun 24 at 12:56
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Zombies are basically human rotting bodies.

To keep them together, they need to supply spare elements taken from a human body.

Eating a human body is the most direct way to get those, considering how clumsy the zombie are for getting food and also how necessarily inefficient is their digestive system.

Since they cannot fully digest food and use those elements back to synthesize bodily components, accessing human intermediates is the best compromise.

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    $\begingroup$ I like this idea it's kind of cool and just sciencey enough to be almost reasonable. $\endgroup$ – Ash Jun 23 at 13:00
  • $\begingroup$ They can subsist for years without humans, so obviously they don't eat only humans. But humans are better and tastier so they go for them. Also, they know females are softer and easier to chew (very important when they have little teeth left). That added to the fact zombies are drawn to sharp sounds explains why they always go for the heroine first. $\endgroup$ – Mindwin Jun 24 at 12:55
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    $\begingroup$ They can subsist for years without eating humans, but it's just bare maintenance at a low baseline without any real advancement or growth. Any meaningful steps beyond that low baseline require a human diet, and without human diet they will slowly backslide to that low baseline. $\endgroup$ – WBT Jun 24 at 13:26
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    $\begingroup$ I like the idea, but it doesn't make much sense. They need to sustain their muscles using the same nutrients as all other animals, and eating a human is no more direct way to get those nutrients than eating a cow or apples. $\endgroup$ – Behacad Jun 24 at 13:50
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It's depends what kind of Zombie we're talking about:

  • Voodoo Zombies, where the word ultimately comes from, attack people because that's what their witch doctor maker/master desires.

  • The Plague Zombie popularised by the Night of the Living Dead films is more akin to the Germanic Ghoul and Umpyr, also the basis for the modern Vampire as popularised by Bram Stoker. In legend, ancient and modern, they hunt humans because they have to consume human life-force or because those humans have in some way wronged them and they're taking vengeance upon them. In film as far as I can remember the answer is pretty much "because they do" no further explanation required or given.

  • The modern Zombie of franchises like The Walking Dead owes more to Ramero than Voodoo with the idea that they attack to spread some kind of "Zombieism" (totally a word) disease that is functional similar to rabies in that it makes its hosts hostile towards other potential hosts.

As a note World War Z (the book don't bother with the movie) has Zombies that are substantially similar to many other modern Zombies but which hunt any fauna, including monkeys, moles, rabbits and at least one rather large alligator.

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    $\begingroup$ Good one for mentioning Word War Z, while discarding the movie. It is the best take on the modern zombie apocalypse of any medium, I've met so far. $\endgroup$ – Lupus Jun 24 at 2:28
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    $\begingroup$ The Walking Dead series shows many instances of zombies (walkers) eating animals (deer, dogs, horses, etc), as well as humans. Less about life force and more about voracious hunger... $\endgroup$ – ChuckCottrill Jun 24 at 4:23
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    $\begingroup$ Or Peter F Hamilton's Night's Dawn trilogy... $\endgroup$ – jwenting Jun 24 at 5:21
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    $\begingroup$ Even a little more let's say hard sci-fi-esque are the zombies in Danny Boyle's 28 Days Later. The zombies aren't even undead, they are living humans made blood-thirsty by some rabies-like virus. $\endgroup$ – nikitautiu Jun 24 at 12:24
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    $\begingroup$ @Lupus I also suggest The Zombie Survival Guide by the same author. It gets into the nuts and bolts of zombies from a practical perspective. $\endgroup$ – Andrew Brēza Jun 24 at 12:45
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Zombies are simply the vehicle by which the zombie virus spreads itself. And the zombie virus, like many viruses, only infects humans.

Zombies of course have a never ending hunger for human flesh. But its not because they need delicious brains to survive. Rather, that craving to sink their teeth into the soft, tasty goodness of a living person is instilled by the virus as a means of ensuring it survives and spreads by infecting others. In a sense, the zombies are seeking out new hosts for the virus. And that host is humans. They don't attack animals (mostly, some may get confused) because biting a cow or horse does not spread the virus.

So yes, zombies will capture and devour terrified humans, ripping their innards apart as they feast upon their screaming victims. But some humans will evade the attack with merely a scratch or bite... and that ensures the virus is passed on.

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    $\begingroup$ So actual "eating" (or at least mauling to death) of humans is an emergent consequence of the zombie's desire to bite. If the target of the bite doesn't escape, it just gets bitten, and bitten, and bitten - possibly by multiple zombies - until, well, maybe until it stops moving and cools down...? : ) Best answer here. IMO. $\endgroup$ – Grimm The Opiner Jun 24 at 11:51
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    $\begingroup$ the human brain is really good at identifying humans by sights, smell, and sound so it is not even that hard to exploit. $\endgroup$ – John Jun 24 at 14:01
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    $\begingroup$ This is the correct answer, far superior to the currently marked one. $\endgroup$ – Muuski Jun 24 at 21:01
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Human brains are easier to convert into human stem cells then deer brains.

The human stem cells are used to repair the zombie body.

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    $\begingroup$ What? How? Why? $\endgroup$ – Raditz_35 Jun 23 at 11:33
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    $\begingroup$ +1 - It makes even more sense than a walking corpse eating. $\endgroup$ – Pere Jun 23 at 20:30
  • $\begingroup$ Finally, a viable explanation for that "braaaains" fixation. That calls for a research project ;) $\endgroup$ – jvb Jun 24 at 20:07
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From the point of view of the storytelling, the cannibalism taboo is one of the stronger and most basic taboos for the people of most of the cultures. If one wants to show the total breakdown of the society and lack of any culture and order (Warhammer Chaos style), the easiest way to depict it is to show cannibalism, necrophilia and incest in whatever order. The second component of the zombie myth is actual reanimation of the body - and that is also one of the oldest, most basic and most widespread fear we can see in the lot of human cultures. So, purely from the storytelling perspective, the cannibalistic undead is one of the easiest trope you can use to evoke dread and disgust to significant degree for the humans of the most known cultures.

If we are looking for the in-story explanation of cannibalism, I see two different explanation strategies.

The first one has less to do with feeding itself. It is a more archaic one, more similar to the traditional vampire stories - by whatever mechanism, the reanimated bodies retain some of the memories and the ability to recognize people. They would attack the people they remember feeling resentment to. Or, more horribly, the ones they felt attachment towards. As in Eastern European vampire stories, such zombies would shamble back towards their home and family, then start tracking and hunting all the people they knew. Such explanation would work well in the low-tech worlds to explain why zombies may walk across the wilderness to the nearest human habitation.

The second explanation is exactly about feeding and presumes that there is a cannibalism taboo. A thing reanimating the body is some sort of a parasite - a biological, psychic or magical one. And unlike the original inhabitant of the body, it sees humans as a possible source of meat. In the modern setting, with the contemporary population density, this parasite doesn't even need to see humans as the only food. A hungry zombie waking in the modern major population center would see hundreds of people around, much more then any other sources of recognizable food.

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Mainly because of these reasons:

  1. Density of population.

    Humans will voluntarily pack more densely than most other animals... they even are known to build cities with high-rise buildings, providing only narrow escape routes, while at the same time reaching a higher meat-per-area ratio than other wildlife. For example Hong Kong has approximately 6,300 people per square kilometre (source).

  2. Nutritional value.

    A human provides 12% of mass in lipides (fat) and 20% of mass in proteins (see composition of human body), resulting in a whopping approx. 155.000kcal (see here). And those are only average values: deviations in body-mass index occur - accompanied by decreased mobility coming along with increased nutritional value.

  3. Almost no defense, easy prey.

    No horns, tusks, protective leathery skin, only insignificant claws and teeth. Bad eyesight, worse at night. Humans often are in need of corrective lenses. Humans are known to utilize tools, but access to more efficient lethal tools is regulated and restricted in most societies.

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    $\begingroup$ Humans have pretty good eyesight compared to other animals. (Certainly better than zombie eyesight, which are just decaying humans) Even with bad vision, they're still pretty decent. bbc.com/future/story/20131101-could-humans-see-like-animals $\endgroup$ – user169179 Jun 24 at 16:56
  • $\begingroup$ @user169179 my cat (cf. my profile pic) may have a different/reduced color perception, but otherwise is literally mocking me when it comes to stalking and making prey (when I walk, she loves sneaking up from behind and just touching my calf, as if I were a zebra - she even does that to the mailman). I learnt 360° situational awareness the hard way (=in the army), but the horse I'm occasionally riding can do that routinely with much less neck action :) Zombie eyesight is probably not better than human eyesight; but I guess humans would be easier prey than deer to both humans and zombies ;) $\endgroup$ – jvb Jun 24 at 20:03
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Wonderful reasons, accurate and informative. I think the true reason over the top of all of these is that eating humans makes it an existential problem for humans. Especially the humans in the story. If zombies were happy with dogs or dog food then the problem is just one of management. Where can we get enough for the zombies to eat that they will leave us alone.

In the (always) post apocalyptic world of modern drama you need a current real threat that requires constant attention.

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  • $\begingroup$ Welcome to Worldbuilding Eliot, when you have time perhaps, you could take the tour and read-up in our help center about how to How to Answer. Your reply to the question is more of a comment on the question than an answer, I know that you don't posses sufficient "reputation" to comment yet, but we would appreciate answer to be answers rather than comments. (From review). $\endgroup$ – Measure of despare. Jun 24 at 16:40

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