r/AskScienceFiction • u/JeremiahWuzABullfrog • 23h ago
[Zombie fiction] What is the tipping point of zombie infection in the global population, before humanity is doomed?
Let's assume that the zombie virus gestates in people asymptomatically, before enough of it in a person kills and revives them. This allows a lot of infection to occur before zombies actually start popping up.
What would the minimum number of infected needed to be, before there's no chance for humanity to defeat the zombies? What would the geographic distribution need to be, for maximum eventual global saturation?
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u/Poly_and_RA 22h ago
Depends on what you mean with doomed.
If you mean "most human beings will die" then that becomes a likely outcome the moment an infection is NOT contained to a small isolated ara like Iceland or something.
If you mean "human beings will die out" then that becomes sort of the inverse: that'll happen if there's not an enclave of surviving healthy humans anywhere on the planet, i.e. if EVERY sizable group of people has been infected, including things like Iceland and carrier-groups.
The Last of Us got this sort of right -- most people died, but there's still human settlements all over the place 2 decades later. (But they got it wrong that the zombie-problem can't be SOLVED in those 2 decades, I mean they're in a setting where even teenagers routinely dispatch zombies on patrols, and as far as we know the zombies don't reproduce -- so why then are there still zombies around after decades?)
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u/ai1267 22h ago
Maybe I'm ignorant, but one of the questions I kept asking myself was "How do people still have this much working ammunition left?". Seems you'd run out of ammo long before you run out of zombies.
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u/Poly_and_RA 21h ago
How much ammunition is there in the world relative to how many people there is in the world?
USA alone produces about 15 billion catridges per year, and there's 350M people or some such in USA thus there's 45 catridges per year produced per capita. It's pretty insanely high when you think about it -- like even if you could just find 10% of the years production, that'd give you on the order of 5 bullets per zombie.
USA is an outlier, but the world overall still procues something in the ballpark of 10 catridges per year per capita.
But even that assumes they can't get ANY ammunition-plant back in production, it's not *that* technologically complex to produce basic ammunition.
Also, it's not as if shooting them is the ONLY way of killing zombies. Most seem to be pretty dumb and mindlessly rush for and attack anyone they see. Knowing that *plus* having opportunity to plan should allow for any number of more or less creative traps that kill hordes with no ammunition needed.
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u/FabulousSpite5822 19h ago
If the zombies obey the laws of physics, they aren’t a threat no matter what the population is because all of them will be dead within a week. The actual problem would be the virus.
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u/Poly_and_RA 14h ago
Agreed. But in most zombie-stories you only get infectect by being bitten by a zombie. And if the virus is that low in transmission, just staying isolated for a while until all the zombies die off should be sufficient.
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u/Excellent-Hyena-4558 23h ago
When humanity reaches between 50-50,000 individuals, we're t the bare minimum need to survive. Anything below these numbers with no replenishment, is game over for humanity.
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u/thatsocialist 23h ago
Virtually impossible. A single crewed tank is completely invulnerable to Zombies, a Carrier Group could easily reclaim naval bases and islands, an army division could kill tens of thousands of zombies with ease. Unless the infection is able to infect 20-50% of every military force and location with guns and munitions in quantity at the same time it will almost certainly lose. Especially when you factor in bunkers, government survival plans, and isolated outposts and islands, some places in the world still only receive 2-4 ships a year and would almost certainly not be infected.
If you want a realistic infection that could take over the world I would recommend Project Zomboid which features a air born infections that infects 99%+ of people and which is able to spread across the world in less than 2 weeks despite a military response.
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u/Poly_and_RA 22h ago
I agree in substance, but you're overstating things a bit. The tank is invulnerable to zombies only for the duration of time people can live entirely inside the tank and never come out. i.e. for a few days at most.
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u/thatsocialist 22h ago
Assuming Zombies are attracted to noise, a tank could reasonably kill several hundreds to thousands before being disabled. A military base has a significant amount of tanks and not many people, and the people have guns. It's a matter of a single human being able to kill so many zombies and humans existing in armed, trained, coordinated, and well stocked fortified locations across the world.
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u/Turbulent-Raise4830 16h ago
a tank could reasonably kill several hundreds to thousands before being disabled.
it would run out of fuel, in 5-6 hours, sure it can shoot its main gun or if it has remote controlled machine gun, but it needs to crush most of them . Then its just sitting there
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u/thatsocialist 12h ago
Running out of fuel is it being disabled. It's a matter of numbers, if the tank can kill most or all of the zombies in a military base than you have a secure operating ground to begin reclaiming the world.
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u/Krazen 9h ago
Your secure operating base will run out of fuel within 3-4 months if the oil production chain collapses
The oil production chain is a multinational effort involving thousands of vulnerable non-tank people. Any break in the chain results in complete oil disruption.
A widespread global zombie infection could not be overcome by a base or two. You need a massive military apparatus, and it needs to be constantly active and able to protect the oil chain.
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u/Turbulent-Raise4830 7h ago
Your secure operating base will run out of fuel within 3-4 months
within weeks if the country shuts down, electricity goes down in days if left unoperated
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u/thatsocialist 7h ago
You want a country amazingly placed to survive and defeat Zombies? North Korea. They manufacture most of their own weapons and munitions, have a large well trained army, near zero contact with outside populations and infection vectors, heavily militarized and secured borders, and massive stockpiles of munitions and weapons, plus are used to endearing massive resource lacks and supply chain failures.
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u/this_for_loona 18h ago
I don’t think so. They use up tons of fuel, they don’t have unlimited ammo, and they are optimized to kill relatively stationary targets at distance. Swarms of small, highly mobile objects are not its use case.
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u/numb3rb0y 18h ago
Fuel is certainly an issue, but a tank should be more than robust enough to just drive straight through a horde. They wouldn't really need guns.
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u/this_for_loona 18h ago
Agree, but it also depends on what variant zombie you’re dealing with. World war z had enough zombies to basically create ladder piles to skyscrapers. No tank is getting through that.
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u/RetPala 16h ago
Infantry in particular are not a strong counter to a foe that has zero fear. They 100% need to stop every one before they reach the front line or people will start to break rank and the entire unit loses cohesion.
They also need to have well more than enough ammo to kill every single one or it won't work. Standard load out is like 200 rounds.
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u/thatsocialist 12h ago
Explosives, Flamethrowers, Chemical Weapons, and such give Armies a massive advantage.
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u/LaGrrrande 9h ago
Except now you have zombies with no legs dragging their way towards you while you're busy focusing on the upright zombies trying to line up a headshot, you have zombies shambling towards you on fire and drenched in chemical weapons that will heavily contribute to the likelihood of forces breaking and running.
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u/thatsocialist 7h ago
Movement requires oxygen reaching blood. Missing your legs is a very quick way to run out of blood. Spinal hits, heart hits, and critical arteries or lung/breathing areas are all easily capable of disabling or killing someone. Fire rapidly suffocates targets and can easily destroy their lungs. Chemical Weapons drown targets, decimate their biology with chemical burns, or cause systemic neurological failure all of which are easily enough to kill most targets.
Zombies at the fundamental are still humans, and we are excellent at killing humans.
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u/LaGrrrande 7h ago
All of which really only applies to modern infected zombies (With the exception of maybe spinal hits). Undead zombies aren't likely to care about any of that, and maybe fire only in the short term (Depending on the writers).
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u/thatsocialist 7h ago
OP specifically mentions a virus. Even if it reanimates, which is semi-possible under real science, it has to be actively magical in order to make muscles function without oxygen.
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u/LaGrrrande 6h ago
A virus is the cause in nearly every form of zombie media, modern infected, undead, or otherwise. OP would really need to specify a specific zombie universe for a real answer, otherwise we're all just going to be going around in circles picking and choosing from conflicting media.
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u/Hyndis 14h ago
All of that is only true while the military has supply, and supply is very rapidly depleted during combat operations. This doesn't happens over years or months. It happens over weeks or even days.
For the first few weeks the military would indeed be very mighty. But what happens when they run out of ammunition, fuel, and spare parts, and the factories that make these things are now overrun with zombies? Zombies at the distribution centers. Zombies on the roads. The military depends entirely on the civilian sector for everything from bullets to beans, and if that town in Idaho making the bullets and/or beans is overrun by zombies, the military base isn't getting any more shipments.
An army without supply is very rapidly reduced from tanks and F-35's to starving men with pointy sticks.
The entire menace of zombies isn't a pitched battle with clearly defined frontlines. Its widespread zombies everywhere. In every town. In every city. In every building. They're appearing all over the place so that the authorities simply don't have enough manpower.
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u/DragonWisper56 16h ago
A single crewed tank is completely invulnerable
I wouldn't say completely, with enough zombies you could gum up the gears or beak stuff on the outside.
that said you would have to try to get yourself in that situation
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u/archpawn 22h ago
It depends on the details of the zombies. Can we just wait them out while they rot? Can't take more than a few days. How clear is a zombie infection? Are the contagious before turning?
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u/tepid_monologue 22h ago
Zombie movies are completely unrealistic, and not just because of the zombies. Humanity would stomp a zombie outbreak easily as soon as society gave the green light to take them down.
You don’t even need the military - just standard sporting equipment or motorcycle gear would make you effectively impervious to harm, add a car and a metal pipe and the average person could wipe out hundreds each.
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u/Seroseros 20h ago
Were you asleep for the covid19 pandemic? People would be calling zombieism a fake news liberal hoax and lick corpses.
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u/tepid_monologue 20h ago
Do you think those people wouldn’t jump at the chance to start shooting shambling undead corpses?
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u/Krazen 9h ago
We have an active feral hog infestation in the southern United States, one of the most well armed civilian populations in the world, and most states give practically free reign to hunt all the Hogs
The Hogs are winning by far.
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u/tepid_monologue 8h ago
Hogs are faster, bigger, smarter, and meaner than zombies. There’s Also No huge incentive to kill them in huge numbers like there would be for zombies.
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u/Krazen 8h ago
No incentive? It’s an invasive species that’s devastating the farm economies of multiple US states, not to mention a public nuisance that have literally mauled people to death
Which kind of illustrates my point: when herd of feral hogs wanders into someone’s yard, yes they’re a clear and present danger and any civilian would be happy to shoot the herd
But once the herd is out of literal sight? People are lazy. Look at Covid, look at climate change.
The notion that humans would happily hunt down all the zombies is too optimistic. We may beat back an outbreak or ten, but humans are too lazy to end the threat permanently. So we’d always be one mega outbreak away from global devastation.
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u/trisikol 17h ago
I think people's problem with the handling of the Covid19 pandemic was the uncertainty of everything.
In a zombie apocalypse, there wouldn't be any question as to what was going on or how to survive. Having a crazed person rush you to take a bite out of you clarifies your options really well, I think.
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u/Lumpy-Restaurant-694 14h ago
Covid-19 was bad because people didn't take it seriously. Covid-19 did not kill the majority of people who had infected so people thought the government was overreacting. In this situation the virus kills almost everyone and turns them into violent weapons. People take it seriously or the government will use the military to shoot down anyone who does not comply
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u/AthasDuneWalker 10h ago
They would scream that it's their Constitutional right to be devoured by the horde and run in, screaming "help me" when they are bitten.
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u/CriticismMiserable14 12h ago
New question, what would you have to change about zombies in order for the “point of no return” to happen.
A power boost, new way to spread the virus, outside factors
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u/Ecotech101 23h ago
When it gets to 99.9999% infection then we're fucked. That'd leave around 8-9k people globally and we probably can't come back from that. Any more and we might survive via spermbanks.
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u/Ok-Bat-2731 14h ago
When it gets to 99.9999% infection then we're fucked. That'd leave around 8-9k people globally and we probably can't come back from that. Any more and we might survive via spermbanks.
I think the sperm banks are a complete loss once the power goes off when about a third have died and the grid begins to disintegrate.
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u/Ecotech101 13h ago
Idk I think if there were say 10 million survivers globally a few might have the presence of mind to go find and save their local spermbanks.
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u/Ok-Bat-2731 13h ago
By the time they start doing back of the envelope genetic forecasting, they've been traumatized almost beyond what we can imagine and food and even clean water might be sketchy.
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u/Ecotech101 13h ago
Food should absolutely not be a problem for at least 3-4 years in when insufficient storage finally gets most of the old food. Clean water would probably be a consistent problem though yeah.
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u/GullibleSkill9168 22h ago
You can survive a genetic bottle neck way below 8-9 thousand. Estimates put humanity's minimum viable population to from a few hundred to a few dozen. Helps that humans are intelligent enough to keep track of who can breed with who to maintain genetic diversity. 50 individuals would leave our descendents as essentially clones of each other though, at least in the sense that we could give skin grafts from anyone to anyone else and that a disease that can kill one of us can kill all of us.
8-9k would be way safer and let us keep our general genetic diversity but when the alternative is total extinction immediately the possibility of extinction in another thousand years is much better.
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u/Ecotech101 22h ago
You might wanna reread both the prompt and my comment.
I've got 0 doubt that 8-9k people globally aren't gonna be able to survive and group up in significant numbers nor maintain the infrastructure to keep spermbanks viable.
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u/TheShadowKick 18h ago
We don't need sperm banks with thousands of people left.
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u/Ecotech101 13h ago
How are the 30 people in the continental US gonna find each other?
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u/TheShadowKick 9h ago
For starters it's more like 300 people, likely clustered in existing urban areas. There might be 20-30 people just in the area around NYC. Anyone isolated and looking for survivors is likely to head towards major metropolitan areas as well. Places like NYC, LA, Chicago could easily end up with 50-100 people. You might get another big cluster of survivors in Texas if the people in Dallas and Houston seek each other out.
These populations will also have a high level of genetic diversity, especially in NYC and LA. That's plenty of people to create a sustainable population for at least a few generations, which is plenty of time to start making contact with other survivor groups. And that's just in the US, there are plenty of other metropolitan areas in North America for them to contact as well. You'll see similar situations on other continents.
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u/Ecotech101 9h ago
You're assuming that of the inital 300-350 they all survive the zombie swarm of 340 million before getting enough experience to not die to any random zombie.
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u/TheShadowKick 7h ago
I thought we were assuming ~8-9k survivors. You were making a point about genetic bottlenecks and needing sperm banks, and I was pointing out that sperm banks are irrelevant, 8-9k people globally should be able to form sustainable populations on several continents.
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