When is a headshot not a kill? The curious biology of The Walking Dead

Title Pic

The Walking Dead. Copyright AMC Studios.

The scene-chewing Walkers in AMC’s The Walking Dead series are a thing of beauty – violent, grisly beauty. The makeup, special effects, and acting combine for a zombie Rembrandt of sci-fi entertainment. I figure since The Walking Dead is in full swing and we just celebrated Halloween, what better timing to sprinkle some science in with our horror stories? As much as I love the Walkers, a key aspect of their biology has been annoying me since the end of season 1. My gripe is simple: how Rick and the gang dispatch the zombies is inconsistent with the show’s “zombie biology”. Mild spoilers ahead.

Let’s be clear, I’m not here to point out everything in The Walking Dead universe that is impractical or unrealistic. We could spend an eternity on that endeavor (how do zombies walk despite lacking a functional circulatory system necessary to feed the muscles that do the walking?). No, I’m fine with whatever rules that authors want to put in their fictional universes. Your zombies are caused by a microbe (bacteria, virus, or fungus) that (Spoilers for Season 2!) already infects the living, but takes control of your brain after death? Awesome! I have no problem with any of that. I do however, have a problem with internal inconsistencies. Namely, that the Walkers do not obey the rules of their own damn made-up world!

We can find a contrasting example of internal consistency in the Game of Thrones universe, where there exist “wargs” or “skinchangers”. They are characters that can transfer their consciousness into animals and possibly humans, as is the case with Bran Stark via Hodor. The universe is internally consistent with this rule in that: 1. The warg experiences what the animal experiences. 2. The warg can transfer their consciousness to an animal when their human body dies (although the warg’s consciousness is lost when the animal dies). 3. Although the warg doesn’t die when their animal hosts do, they experience great trauma over the ordeal. These are situations that logically flow from how “warging” works in this universe.

Now what’s the problem with The Walking Dead? Well, you might have been paying attention at the end of season 1, where the gang reaches the CDC in Atlanta. Here they meet Edwin Jenner, a doctor that explains to them that the Walkers only possess reanimated activity in the brain stem. No problem! So these zombies only have a functioning brainstem….what is a brainstem?

brainstem and brain

Copyright of The Stroke Network. All rights reserved. Obtained from here.

Your brainstem is composed of separate components called the medulla, pons, and midbrain. It’s basically the conductor of your central nervous system, relaying sensory information from your brain to your body and vice versa. It also controls your heart rate and breathing. So what’s the rest of that big ol’ brain used for?

brain senses

Ask a Biologist. Funded by National Science Foundation and NSDL. Arizona State University School of Life Sciences: an academic unit of the College of Liberal Arts and Sciences. Obtained from here.

According to this figure, a lot. Do you see the issue? Everything the Walkers do in this universe – like reacting to sight, sound, and smell, or even just walking itself – is dependent on non-brainstem parts of the brain! The Walking Dead zombies shouldn’t even be walking, much less finding their victims through audio-visual cues! However, I’m willing to forego this little conundrum. Scientific knowledge is constantly changing, even in this universe. Maybe that zombie-causing pathogen found a way to re-wire the brainstem to perform these tasks, and the researchers just haven’t figured it out yet. Fine, but let’s talk about those gore-iffic zombie kills.

I’m going to pick on fan favorite Daryl Dixon for this particularly egregious example. Take note of where the arrow is going through the zombie’s skull.


The Walking Dead. Copyright AMC Studios.

By the series’ own rules, this is not a zombie kill, as the brain stem is unaffected. Daryl should still be fighting for his life against a now cartoonish arrow-through-skull walker. Let’s take a look at a more effective method.


The Walking Dead. Copyright AMC Studios.

Hell yeah! Way to go, Martinez! You bashed through that soft, nougaty center to get to that pesky brainstem inside. This would count as a true zombie kill in this universe. Other effective methods that target the brainstem include cranial skewering via sword or pickaxe, back-of-the-head shots, and decapitation (followed by eventual skewering to silence the gnashing head).

I don’t think it’s too much to ask for my escapist fantasy series to be internally consistent. Any rules a fictional universe wants to create are fine by me, but please don’t blatantly ignore them when it concerns the main characters. Shows like The Walking Dead and Game of Thrones are wildly entertaining, and such attention to detail would deliver a story that is both emotionally and intellectually satisfying.

About the author:
austen_avatarAusten is a fifth year graduate student and president of Science ACEs. His dream is to go fishing every day once he’s finished with this bacterial pathogenesis thing. You can follow him on twitter @AustenLeeT



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