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Is it possible for humanity to completely annihilate itself? By that I mean there cannot be one survivor left and the annihilation must be caused by humanity itself with current technology (no crazy AI killing everyone) and not by natural disasters (no giant meteorite).

The following come to my mind but won't achieve 100% annihilation:

Nuclear war: There will still be some survivors and some place on earth will have tolerable radiation levels.

Genetically engineered killer pathogen (virus/bacteria/parasite): Because our gene pool is so diversified, some people will naturally be immune to it, some people in remote area won't catch the pathogen.

Desertification/Global warming: Some areas near the poles will still be fertile.

Mankind is kind of tough to get rid off!

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  • $\begingroup$ Wait so an AI is too artificial but engineering a supervirus' genes isn't? And natural meteors are out of the question but global warming, an inevitable process no matter what changes we make (Although we can change the speed) is not? $\endgroup$ – Zxyrra Nov 25 '16 at 4:04
  • $\begingroup$ Yes. See articles on the Permian-Triassic extinction event, and compare that to the current situation WRT fossil fuels. $\endgroup$ – jamesqf Nov 25 '16 at 4:43
  • $\begingroup$ GMO human like it or not... $\endgroup$ – user6760 Nov 25 '16 at 5:46
  • $\begingroup$ Just go with a double whammy, mass extinctions happen when multiple stressors all happen at the same time. don't pick just one start combining things. like a nuclear war combines with a plague or a climate change topped off with a bolide impact. $\endgroup$ – John Nov 25 '16 at 6:24
  • $\begingroup$ I would imagine that a nuclear war followed by a rampaging genetically engineered killer pathogen would leave very few humans left alive. But they face the problem of limited food and water, because the soil and rivers have been poisoned by the nuclear war, as well as the fallout and "nuclear winter" - they may have a tough time finding a mate too if they happen to be spread few and far between. If there isn't a concerted effort to get the human race going again, it may well go extinct. $\endgroup$ – colmde Nov 25 '16 at 11:23
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8 Possible Methods

Superbugs (Intentional)
An act of biological warfare planned extremely precisely may be able to wipe out the global population. It's not likely, but then again, nothing is likely to completely annihilate all of humanity; life finds a way.

If a virus, bacteria, or prion is designed to kill with the most efficient incubation period, methods of spread, etc. and planted in multiple countries (or even better spread by drones through the air near airports and in major cities across the world) it may be able to kill the population relatively quickly. As with all of these methods, people in isolated places like Antarctic research stations and the International Space Station will not die so quickly - it will have to be from a lack of resources.

Note that this pathogen must specifically be delivered to isolated places - remote islands, cruise ships, etc. to really kill everyone - but that those who survive may end their own lives.

It's also worth mentioning that an engineered pathogen need not worry about "natural immunity" - there are bound to be ways to bypass this if you can make the perfect biological weapon.


Superbugs (Unintentional)
Similar to the above - however, this involves unintentional human actions creating a pathogen, which, by pure luck, conquers the planet. Very unlikely, but not impossible.

We're already creating "superbugs" every year by overusing antibiotics. In cramped, industrial sized farms, livestock in bacterial breeding grounds are pumped full of too-strong antibiotics. The bacteria that survive proliferate, and, when their ancestors are exposed to the new rounds of stronger antibiotics, the ones that survive reproduce, and so on - until we're left with multiple recorded cases of bacteria we don't know how to kill.

All it takes is a bacteria that can be transmitted to humans, with negative effects and high transmission - and the pure luck to kill us all.


Nuclear Warfare
A dispute between countries, or better yet countries with nuclear allies against countries with other nuclear allies, may cloak the planet in radiation. This would poison and kill much of the civilian population, and only a handful of people in bunkers would survive. Astronauts would starve before NASA could get them down, and Antarctic researchers would likely meet the same fate.

Those in bunkers likely wouldn't survive due to nuclear winter: clouds of soot would lower global temperatures, meaning people emerging from their bunkers (provided there was enough food) would not be able to farm efficiently. Additionally, it has been suggested that this type of event would destroy the ozone layer - showering the frozen Earth with deadly radiation, complicating or ending complex life for a very, very long time.


Overcrowding and Resource Mismanagement
Following some models of population growth, the Earth may run out of space and resources before we solve the problem of overpopulation itself. While this will cause mass deaths, the remaining population can still get by. Eventually, these cycles will deplete the Earth's natural resources. According to Stephen Hawking, we must leave Earth, or else this is what will end humanity.

The problem with leaving Earth after we consume it (think WALL-E) is that we do not have economically viable means to transport thousands, let alone millions or billions of people to another location - the majority of people will be left on Earth as the population starves.

Those not included in "the majority" may actually be doing fine, in a colony on Mars. In order for the colony to sustain itself without requiring materials from Earth, it must be able to mine for every possible mineral used in every computer or robot part, grow every type of food needed without new shipments, refine and process all materials, maintain electricity (nuclear batteries and solar panels only last so long), and find water (groundwater reserves are great but they may dry up), among other things. I wish these colonists luck, but it probably won't work out.


Grey Goo and Ecophagy
A slightly more "out there" approach. This suggests that we will develop the field of nanorobotics to the point that we create swarms of self-replicating machines. These swarms could, if not controlled, grow exponentially, devouring ecosystems in their quest to reproduce. Supposedly they may be able to sterilize the planet; whether this scenario is actually realistic is up to you.


Evolution
A less depressing method, this suggests that humans will evolve over time until we become a new species - compare humans to our primate ancestors - which would technically mean humans "annihilated" themselves just by reproducing.

While this is a clever approach, it may be less likely than the above scenarios. Evolution favors isolated populations - see the biodiversity of the Galapagos Islands - because traits can be passed throughout the species relatively quickly. There are over seven billion of us, and we can travel anywhere, to reproduce with (evolutionwise) anyone. Any new changes made will be watered down, fast.

Additionally, humans don't need to change, so they may not. In a world where antibiotics and surgeries sustain those who can't cope with "survival of the fittest" we may not be pressured environmentally to adapt.


Triggered Supervolcanism
Another slightly out-there suggestion, although not impossible. This suggests that something like a nuclear weapon can trigger or speed up a supervolcanic eruption slated to occur soon. Such a release, multiplied by the number of supervolcanoes in the world, may be comparable to a nuclear winter, which, as described above, would be more than enough to wipe out humanity.


Pissing off the Neighbors
Very unlikely, but I'm including it for fun. If humans anger aliens with weapons of mass destruction - capable of sterilizing the Earth's surface - we will indirectly result in our own annihilation.

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  • $\begingroup$ Hard to see how overpopulation could result in humanity annihilating itself. If overpopulation did result in resource shortages severe enough to cause massive numbers of deaths, at some point those deaths would reduce the population to the point where it is sustainable. For example, if we really got to the point where we were using all available farmland as efficiently as we know how, and we still didn't produce enough food to feed everyone (and there's no technology to synthesize food from dirt or whatever), then okay, there's starvation and millions die. But eventually you reach the ... $\endgroup$ – Jay Nov 25 '16 at 5:07
  • $\begingroup$ ... point where the food production matches the population, and you have a new equilibrium. $\endgroup$ – Jay Nov 25 '16 at 5:08
  • $\begingroup$ @Jay I considered that, but note that the planet's resources are finite. We can keep cycling between more people and less, more and less, but eventually the pollution, lack of fertile soil, etc will build up, and there won't be new farmland to seed or forests to cut; maybe a better title for that section is "Resource Mismanagement" $\endgroup$ – Zxyrra Nov 25 '16 at 5:13
  • $\begingroup$ But it's not like there are a fixed number of trees in the world and once we cut them all down, they're gone, Trees grow back. Ditto fertile soil: farmland is only "used up" if it's mismanaged. One could imagine a scenario where people drive all trees to extinction through mismanagement, but wow, that's a very extreme scenario. $\endgroup$ – Jay Nov 25 '16 at 5:26
  • $\begingroup$ @Jay One could also assume that growing needs for population space would seem more important than having big, open fields; it's easier to eat less than to have less kids. We'd lose farmland with each new population cycle, and at some point it may become irreversible $\endgroup$ – Zxyrra Nov 25 '16 at 5:30
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Do you mean theoretically, or in practice?

Theoretically, the answer is surely yes. One can easily imagine hundreds of scenarios. Take a simple one: For whatever reason, half the population get knives or guns and kill the other half. Then the survivors kill each other. Etc etc until there is only one person left, who commits suicide. Or maybe the last two people simultaneously shoot each other.

In practice, I don't see any likely way for it to happen. As you state in your question, every disaster scenario you can think of, there would always be some number of people who through foresight or luck manage to survive.

In a war, surely some would survive in bomb shelters, or just be fortunate enough to be in an area not targeted by whatever weapons we're supposing. You don't even have to suppose they are in the Antarctic or something. Even in a nuclear attack, surely there would be places in, say, Wyoming or South Dakota that are not hit with missiles, and are far enough away from targets that they don't suffer serious fallout. And surely there would be many countries not involved in the war at all. If, say, the US and China fought some terrible war, it is far from inevitable that Argentina and Botswana, etc etc would get involved.

Any sort of environmental disaster would take many years to unfold. If billions of people were really dying because of pollution or global warming or global cooling or whatever, surely at some point people would decide to take action. Either to save the planet or at least to create some sort of enclave to save themselves.

It is conceivable, of course, that people could do something -- whether through war or indifference to the environment or whatever -- that literally makes the entire planet uninhabitable quickly enough that no one can react to save even a small remnant of the population. Or that people do something that sets forces in motion and no one realizes the danger until it is too late to stop it. For all our vaunted technology, I doubt that humans are really capable of destroying the planet. And even if we are, surely someone could see it coming and build a self-contained underground habitat where a small number can survive. Or send a small number of colonists to another planet. Or some such.

You'd need something that either, (a) literally destroys the planet, blows the world into a million pieces; or (b) happens so quickly that no one has time to implement a plan to save even a small number.

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  • $\begingroup$ "there would be places in, say, Wyoming or South Dakota that are not hit with missiles" while this may be true, you are completely ignoring other climate impacts (giant clouds of particles, ozone depletion) that would impact "Wyoming or South Dakota" $\endgroup$ – Zxyrra Nov 25 '16 at 5:48
  • $\begingroup$ I completely agree with the last two points (a) and (b) I considered those when writing my answer, then quickly discarded a in search of less extreme sterilization $\endgroup$ – Zxyrra Nov 25 '16 at 5:50
  • $\begingroup$ consider population size though many of those place don't have enough people with enough variation to produce a stable breeding population. $\endgroup$ – John Nov 25 '16 at 6:19
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    $\begingroup$ @zxyrra I'm not ignoring them, just trying to say that I suspect that in a real-world scenario, such fallout (in the general sense of the word) would not render places far from targets uninhabitable. As no one has ever performed the experiment -- and I'm not saying that I'm hoping someone does -- any predictions are speculative. $\endgroup$ – Jay Nov 25 '16 at 6:32
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    $\begingroup$ @john If the number of survivors is small enough, sure, inbreeding could be a problem. But it's unlikely to be a problem that would result in 100% of the survivors dying out. Of course there's no fixed number where inbreeding is not a problem -- it's not like 10,000 and the population will go extinct but 10,001 and everything will be fine. And the number depends on how diverse the initial population is. But I'd think a few thousand survivors would be fine. Isolated towns of a few thousand have survived with little apparent problem. $\endgroup$ – Jay Nov 25 '16 at 6:36
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Rooting humanity is next to impossible. Meteors can be diverted, also safe havens could be built underground. There will be survivors to a nuclear apocalypse. A group can hide from gaze of an homicidal AI. Global warming will not affect underground bio-domes built to survive that disaster. There is only one way to root out humanity: destroy the planet, and fast. Otherwise they will run out to other stars.

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  • $\begingroup$ this is what i came here to say - with our current tech, no, we couldn't wipe out 100%, 99% maybe, but not every single one of us. $\endgroup$ – Jimmery Nov 25 '16 at 18:42
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Sometimes the simplest things are the most efficient.

For the result you have in mind (since you are not stating a time frame, only a tech level):

Just throw a rock.

Admittedly it would need to be a big one, but space is not only huge, mind-bogglingly huge, it also contains rocks of various sizes.

So, let's build an unmanned spacecraft, send it out to a suitably lump of mineral, and push it a bit, so it's altered path eventually makes it collide with our planet.

Provided your rock is big enough, you can make really big splash, killing everybody.

A big bonus: from the moment where anyone notices what is happening, there is nothing mankind has in it's arsenals to stop i from happening.

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I tend to agree with Cem Kalyoncu, killing off 100% of humans from this planet with our current tech would be near impossible.

Without creating a super air-bourne virus, or a deadly AI, or gaining the space-tech to throw a big enough rock at the planet, there would still be people left.

We could even adapt to environmental changes caused by global warming or a nuclear winter. Many would die, yes, but there would always be some survivors.

The only scenario I can think of, without creating new scientific discoveries, where we would all die is if we regressed technologically. Our advance of technology stopped or slowed. And never advanced. Ever.

Not even after thousands of generations. No technological advances even after millions of generations - then the sun will grow big enough to wipe us all out.

If we do nothing, and stay on this planet forever, it will eventually take us out.

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A nuclear war with a sufficient amount of Cobalts bombs, can cause the extinction of most life form on earth, humans included.
However the life still survive, because there some species of bacteria extremely resistant to radiation, like Deinococcus radiodurans.
If in future we are able to create an antimatter bomb, with a simple war we can wipe out the entire planet.

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Release a disease cocktail all at once. Release small pox, plague, measles, hepatitis, malaria, aids, flu, ebola, anthrax, tuberculosis, etc.

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Convert the world's supply of h-bombs to cobalt bombs. Detonate. There will be no long term survivors. You're not going to be able to hide out in your shelter long enough.

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Yes, and it almost happened. In the Cold War, both the US and the Soviet Union had more than enough nuclear warheads to wipe out not just humanity, but all long-term life on Earth. Graphic of US and USSR nukes during cold war] The USSR had over 35,000 warheads at the peak of the conflict The US had over 30,000 warheads at the peak of the conflict

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