Okay, everyone please remember that this is by request. This may take multiple comments, and it might take me a day or two to finish up, assuming I don’t have stuff get in the way.

So, zombies.

They aren’t actually entirely fiction. Back in the era of slavery in the “new world”, multiple religions and practices ran into each other. Enslaved peoples from multiple African regions, and the indigenous peoples of the Americas and islands, were forced to convert to christianity. Those indigenous peoples and the African peoples didn’t exactly stop believing what they believed, but they applied camouflage to those beliefs of christian mythology.

Thus arose the various syncretic religions often referred to as “voodoo”, though there are at least three major branches of the general heading.

One of the practices of some of those religions is what we might call magic. Now, whether one believes that ritual and spells and such can do anything, those practices exist, it is a factual thing.

One of the many “spells” is turning someone into a zombie. There are people today that are “zombies”. That they have never been dead, and the only thing that changed was maybe a bit of brain damage from the use of toxic and psychoactive substances on them is irrelevant to this. They believe they’re zombies and so do other people. That’s the word for people in that situation, and all of the other versions take their name from that.

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From there, you go to white folks discovering zombies. The first zombies in movies go back to the thirties. And that’s really when the journey of the zombie starts in the kind of terms we’re talking about for this. There are much older “undead”, in pretty much every culture, but the Haitian origins of the word zombi are the root of all modern zombie fiction, if not always intentionally.

But the original movies were pretty much just an exaggerated version of the real world zombies. Now, those were based on books like “the magic island”, but it wasn’t until film took up the idea that things would diverge significantly.

From there, it wasn’t until George Romero that we had the first major change to the overall fictional zombie. Night of the living dead exploded zombies into broad pop culture. This was in part due to how the movie was released, imo, but that’s too tangential to cover.

This is where we get to the brains meat of the subject.

Post Romero, zombies caught the imagination of the world. The idea spread like a zombie virus until each new writer of a script or book added their own imagination to the mix. Now, there’s so many versions of zombies that you might well not be able to call some of them zombies at all, if compared to the origins.

However, there are still some general categories of zombie.

Magical, where the zombie is created by some variety of spell, ritual, deific intervention, or otherwise supernatural cause. You’ll run into this mostly in books rather than movie.

There’s pathogenic zombies where a virus, fungus, bacteria, prion, or an imaginary microbial life form causes the zombie to rise, or the human to turn.

There’s “chemical” zombies, where some (usually unnamed and mysterious) substance causes the event. This includes radiation zombies.

And there’s the parasitic/symbiotic zombies. This is when a complex and possibly intelligent life form takes over the dead or living body. Might be alien, might be an insect or something similar.

There’s arguments to be made for more types than that, or that some should be combined, but this is my essay lol.

There are, however, two main sub divisions of each of those: slow and fast. You’ve got the shambling zombies and the fast movers. Some of the fast zombies are faster than a living human could be.

There’s also the transmitted vs single event subdivision, where the ability of zombies to make me zombies is or isn’t present, but you really don’t run into zombie movies or tv shows where they can’t transmit the “infection” in one way or another. The genre of zombie fiction relies on the idea of a zombie apocalypse much heavier than it did in the past, though, so I don’t consider it a main subdivision the way speed is. If you include books, it becomes a bigger factor, but zombie books don’t have the cultural weight as movies and serial shows currently.

Okay, so we’ve got that down, and I still haven’t addressed the realism of those things on a physical level. I’m going to cover that in a second comment as a response to this one. Again, folks, please remember that this is something Don asked for, and is in response to that.