The Biology of Zombies: A Primer

Part 1

Zombies have been around for quite some time. But over the years, we have seen an evolution in zombie biology. What I have noticed is that as we begin to better understand science, our zombies change. In many cases, our zombies reflect what we don’t understand about biology. As you will learn or already know, coming back from the dead is pretty hard to do. In this primer, I simply want to inform my readers as to the basic science behind our evolving zombies.


Of course we must start here. Introduced in Night of the Living Dead, George Romero gave us a ghoul that originated with radiation from a crashed satellite.  During that time, radiation was something horrible, something to be feared. It played well to create this undead creature that attacked us.

Radiation is pretty nasty stuff, at least some of it. There are two classifications: ionizing and non-ionizing radiation. Ionizing radiation is what we should be concerned with because it does the most damage. This type of radiation has such high energy that it knocks off electrons from atoms. As you might have guessed, this is not good. This can alter DNA, rather it can destroy DNA. This is why high radiation exposure leads to cancer and sometime immediate death.

There are a few hypotheses as to how radiation could create a zombie. Because of the high energy that radiation releases, this energy would somehow reanimate the dead on a cellular level.  Some would say that radiation would affect parts of the brain that would cause a living person to become a zombie.  By destroying parts of the brain, leaving other parts intact, we could get the characters for attacking and killing others.

Probability: There are a few problems with radiation being something that creates zombies.  Because if its destructive nature, it would affect the whole body, not just the brain and that person would probably die quickly. This could, however, explain why a zombie looks the way it does. Radiation could cause burns, sloughing flesh, and hemorrhaging.  It could even be the answer as to why zombies don’t decay as quickly as a humans.  Decay is attributed to bacteria decomposing tissue, but radiation could kill those bacteria, slowing decomposition. But the biggest problem: the bite. Radiation zombies couldn’t make other zombies through a bite. And I don’t know about you, but I like my zombies, like I like my women: biters.


There are things that we know and there are things we don’t know about parasites so there are many possibilities here. Most of us have had a parasite at one time. It might not have caused any issues, so you probably didn’t know. There are many different organisms that act as parasites: Fungi, protist, roundworms, flatworms.  Most parasites need more than one host to complete their life cycle. For those that infect humans, we are almost always the final host in which they reach maturity and have sex in our body. Yeah, kinda gross and kinky.  We then shed the eggs  or infective stages to the environment to infect their next host. Many of our parasites live in or around our gut. Some hang out in our lungs or liver, others live in our intestines where we feed them when we eat. The really cool thing about parasites is that they are adapted to our bodies and are able to sneak past our body’s defense system. Our body tends to catch those parasites not meant for us, however that can sometimes be bad as our body can overreact causing tremendous illness.

Humans have some pretty crazy parasites, but other organisms, usually invertebrates, take the cake.  I’m sure you have heard of zombie ants, or zombie snails.  All are very cool. I’m saving the zombie ant for the next article on fungi, so be patient.  These parasites are able to take control of some aspect of behavior in these organisms. It’s  a lesson in how brain chemistry alters behavior, which as humans, we do that now without parasites. However, parasites usually can’t make a switch to a different host. At best they might can jump to related organisms, but not to a completely different host like humans.

Probability: For a parasite to make us a zombie, it has to be a very specific type of parasite to affect our brain.  And getting into and surviving our body is a tricky thing. Controlling our brain is another big deal as we are fairly complex. For example, the same medication can act differently in individuals based on that individuals metabolism and body chemistry. However, there is some support here. A parasite, called Toxoplasma gondii, could be altering our behavior.  There is some data correlating higher incidences of risky behavior, crash crashes, promiscuity and dementia in individuals that are infected with this parasite. To add to that, somewhere around one-third of the population has been infected with this parasite. However, most people are asymptomatic or they are able to shed the parasite. Oh, and you can get it from your cat. Yes, they are secretly trying to kill you.

In the next article of the series, Fungi and Prions. Stay tuned.

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Written by Brandon Lowery

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