So, I’m surprised that this debate doesn’t happen more often. Let’s assume that it is a virus or bacteria that kills people, and then causes them to reanimate into zombies.

Those zombie go out and spread the virus by biting other people.

But, even though zombie (assumed) require less nutrients to keep going, they still need some nutrients.

So, do zombies bite other people because the virus or bacteria tells to them propagate, or do they bite other people to feed, and that just happens to also spread the virus or bacteria?

Sub-topic: What if it’s a mixture of both? What if the virus or bacteria treats zombies as having a hive-mind, and only eat enough to keep going, while leaving enough intact flesh to propagate the virus or bacteria?

Zombies make no scientific sense. They’re magic, and should be treated as such.

I agree: magic.

Zombie stories are wish-fulfillment: we get to imagine ourselves slaughtering those who annoy us, with no consequences for our badass aggression.

It’s madness to even complain about how little sense zombie scenarios make. And yet I do. It’s like I’m sick.

The answer to the OP’s question depends on what “universe” (book, movie, TV series, etc.) we’re talking about. But at least some of them are science fiction rather than fantasy, in the sense that they try to give at least a quasi-plausible explanation rather than just treating zombies as magic.

Exactly. Realistic zombies would be no real threat, and so make for crappy stories. Even with magic zombies, the stories only work when survivors have horror-movie intelligence.

“Hey, let’s get some rudimentary weapons and go to heavily-infested areas to poke around and make noise!”

“Okay, but if someone gets bitten don’t say anything. Just come back to our only safe haven and turn, killing your friends and family. Those guys that kill themselves before they become a danger are such Debbie Downers.”

“Deal! Where’s my mp3 player? I like to crank the volume while I poke around, tune out people shouting warnings, zombies shuffling up behind me, all that racket.”

“Smart. You’ve still got power for that thing?”

“Sure! I rigged it to use the batteries from my walkie-talkie.”

“How’d you learn to do that?”

“Traded this guy all my extra ammo. No worries, I’ve still got one bullet.”

“Sweet! Should we take the well-maintained vehicle full of fuel?”

“Nah, that vintage Ferrari is fine if you spend 15 minutes to get it started, and if anything goes wrong, finding parts will be a cinch. So, if we each take a nap now, we can be there just as it gets dark!”

I think the best scientific treatment of zombies was probably Niven’s “Night on Mispec Moor”. There, the zombies are re-animated by a fungus, which uses the mobilized corpse to spread its seeds. The fungus infects a dead body, and the dead body acts instinctively to try to make more dead bodies. The body only has its own reserves of energy to draw upon, and so can’t last more than a night or so before collapsing into a heap of what will become fertilizer for the next generation of fungus. A single human being is still smart enough to come up with an effective defense against them, and manages to last out the night… but then, we’re not the hosts the fungus evolved to exploit, and it works a lot better with the dumb local fauna.

That depends on the zombie. To paraphrase Dead Beat from the Harry Dresden series:

Butters: “Those didn’t act like zombies are supposed to, they were more like the Terminator!”

Dresden: “If zombies were all slow, weak and clumsy like in the movies who’d bother making any?”
And of course then there’s Sue the zombie Tyrannosaur…

Yeah, but those are *magical *zombies. Magical zombies are cool. They make sense, within the limits of the genre - they can walk and move because they have an animating force and magical source of energy. They’re the impossible I can accept; “scientific” zombies are the improbable that I can’t.

Bottom line is the energy to move a body around has to be coming from somewhere. Obviously, the digestive system of the formerly living person is not functioning and cannot provide that energy.

So what’s left? The only other source of energy that wouldn’t be completely magic is the corpse itself. The virus could conceivably both animate the body and simultaneously consume the body as the means to provide energy for the animation. But in that case you’d expect rapid decomposition - a zombie should consume itself within a day or so.

I prefer it when they are magic zombies. The ones that are supposed to be more plausible are so much worse.

The Forest of Hands and Teeth is particularly bad for its zombie biology.

[spoiler]The zombies have been zombies for decades. The entire world is covered in zombies and has been for dozens of years. There are only a few pockets of non-zombies. Zombies don’t eat other animals or other zombies, just humans. But there are only a few humans, the zombies get like one human a year but are still sprinting all over the forest. And sometimes they just bite a human instead of eating one.

So. No food, still energetic, not dying off, what?

Don’t even get me started on their inability to climb a fence.[/spoiler]

alright! ! somebody else here reads the Dresden Files, very cool

Our muscles move because of nerve impulses, but they depend on a steady flow of oxygen and nutrients to continue to function. No “zombie” could exist for anything close to the duration of movie zombies. Their motive muscles (legs, arms, etc) would break down in extremely short order. Moreso if they were typical movie zombies that were constantly shambling around for no reason. The zombie would also experience rapid loss of sensory input as the eyes dried and failed, nerve endings died, etc.

Even if the re-animating virus kept the body ‘functional’ to the point of heart beating, lungs breathing, something we never see in movie zombies, it would be vulnerable to blood loss, which means ordinary wounds would kill it. Hell, a paper cut would eventually bleed out a zombie if the body’s normal healing processes were disrupted.

And as I always say, I’m in Minnesota. We would just wait for winter. I’m not talking about freezing, I’m talking about constant freeze cycles. Zombie out in the sun on a 25 degree day? Well the parts in the sun are going to thaw out. Much worse for the zombie if the brain thaws enough for it to start thinking and trying to move, because partially thawed/partially frozen body parts are going to tear themselves apart. And that is completely ignoring the frost damage destroying the very cells it would need to be able to move with.

So no zombies, not ever.

The closest we could come are the rage zombies from 28 Days Later, and although I’m less familiar with them, I expect they have their own impossible flaws.

And even there…well…I guess I shouldn’t spoil the ending…

It turns out to be a fantasy story at the end!

Jolly clever story, truly!

I’m a comic book collector, and I’ve noticed that there is a brand new zombie comic series starting about once every three weeks. I’ll buy issue #1…find it dreary and uninteresting, and I never see a subsequent issue.

(Exceptions: Antarctic Press’ “The Last Zombie” was well-written and very well illustrated.)

Now: in reality, there are microbes that really do impel their hosts to perform some very specific behaviors, so the idea of a zombie virus that makes people bite other people is not wholly insane. Pica, the disease that makes people eat dirt, is a real thing, and there are conditions that cause people to bite their own fingers.

Animating the dead? No… But what if zombies are actually alive, just severely impaired by the virus affecting their brains?

Hyper-infectiousness? Again, no… But there was the 1919 world flu pandemic. Diseases can – and have – gotten totally out of control.

The zombie plague is a strong exaggeration of real effects, and that’s a good part of what makes it scary as a dramatic motif.

(The Reticulan xenomorph from Alien is scarier when you know about the reproductive habits of the ichneumon wasp.)

I don’t remember any indication of what you spoiled there in the story… Remind me?

The zombies in 28 Days later starved to death, since they weren’t smart enough to feed themselves.

While I’m sure one can still pick nits with it, those zombies seem to be the closest to “realistic” as the genre has come. They basically had super-rabies.

They also moved fast, so getting bit by one didn’t require the hero to mindlessly stumble into them.

Surprisingly, I haven’t read that Niven story, and I thought the fungus approach was one of the more reasonable ones for “scientific” zombies long before I heard of cordyceps. My general thought was that the fungus essentially hijacks the skeletal structure, growing long strands capable of muscle-like contraction along the bones. The corpse’s own muscles and other tissues are just a nutrient source; a densely packed mycelium forms in the abdomen as it consumes the internal organs and is conveniently placed to absorb anything the zombie swallows. Where it falls down (so to speak) is that it has to assume the fungus has developed the ability to coordinate the movement of the bones enough to shamble around, and enough awareness to use the corpse to seek out more nutrients. That’s a big leap, and not something that would happen suddenly. (When someone reports a slime mold moving sticks to lever itself over an obstacle, maybe we can start to worry.)

The “infected” model just makes more sense. Something infects people and causes brain damage that encourages behavior conducive to the success of the infectious agent. For “zombie” infected, that would be wandering around, trying to bite people. (It could just as easily be damage that causes a sensation of raging thirst, so the infected seek out water sources and drink until they puke, contaminating the water. That’s not classic zombie-like behavior, though.) The problem with the infected is that they aren’t dead, so they aren’t really zombies. That interferes with the guilt-free mayhem: when you’re gibbing masses of the infected, you’re killing people.

Do zombie tyrannosaurs have any assets worth going after?

There are no zombies in 28 Days Later

Infected people, still alive (but terribly insane), not undead.

Yeah! Those are called zoombies cuz they’re fast.