Let's say there was a Type II Kardeshev Scale civilization that suddenly went extinct. Why would the entire species just die out? An added condition is that they knew of their impending destruction well ahead of time to make preparations to preserve the detailed record of their civilization.

I was thinking maybe supernova, but if they had other members of their species on different planets, this would not be a plausible reason for their species wide extinction. Maybe a biological "expiration date?"

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    $\begingroup$ So, your hypothetical civilisation were aware of the impending extinction and didn't act to prevent it? Did they accept their fate? $\endgroup$ Oct 29, 2018 at 23:59
  • $\begingroup$ You want the species to expire, but artifacts to stay intact? No robots, no AIs to carry on? $\endgroup$
    – Alexander
    Oct 30, 2018 at 0:06
  • $\begingroup$ Yes, they are resigned to their fate and no, they left no one behind. Just their stuff. $\endgroup$ Oct 30, 2018 at 1:33
  • $\begingroup$ worldbuilding.stackexchange.com/questions/83358/… $\endgroup$ Oct 30, 2018 at 12:40
  • $\begingroup$ of all the civilizations that went extinct on earth we still have descendants of the citizenry, you are aware? usually a civilization going extinct means a break in the archeological record, i.e. certain art styles being dicontinued, certain archtectural details not being found after a certain date, signs of major hubs losing influence, money and documents ceasing to be continued, etc. those people did not all die, they were enslaved, dispersed, or otherwise disconnected from their heritage. A civilization is not a set of people, but a set of cultural details. $\endgroup$
    – bukwyrm
    Jul 23, 2019 at 5:20

12 Answers 12


Too Much Tampering with Genetics

Stargate SG-1 had a species called the Asgard. The Asgard modified their own genetics for multiple reasons - curing diseases, better life spans, smarter, more adaptable. The baseline Asgardian genome had become lost to time. At some point, the species recognizes that there is some subtle flaw with their modification technology that did not manifest until it has compounded too much over the generations to correct. Their gene editing technology is now turned towards curing the problem, but they are able to accurately predict when - absent some unforeseen miracle - their species will end. They make plans for an orderly transition of their knowledge to others.

The Final Solution, Oops I Needed Them...

Babylon 5 had a race whose name escapes me at the moment. The species decided that one ethnic group needed to be cleansed. Later, the species contracts a plague that xenobiologists studying genetic databases show could have been cured by transfusions from the now extinct ethnic group (they possessed some blood abnormality much like some human ethnic groups are prone to sickle cell)


A lot of science fiction has a species transcending physical forms - either becoming pure energy or robotic. In 'Childhoods End' Arthur Clark imagines humanity going through the process. Only the last generation has a ticket to the good life. Their parents will die off sterile. The ascended species, for some reason, will not rescue their race. Those left behind have a whole lifetime to put their affairs in order.


A few authors have explored species developing a kind of Alzheimer's that completely strips them of sentience. Later races walk among what they think are native cattle, feeding their children on their milk and marvelling at the technology left behind by some vanished race, little knowing that race is right in their midst (I think this was in Fredrick Pohl's 'Gateway' and the species intentionally de-evolved to escape the notice of the Assassins)

  • $\begingroup$ Thank you so much for A) the great ideas and B) the amazing references!! A fellow SG-1 enthusiast! $\endgroup$ Oct 30, 2018 at 1:32
  • $\begingroup$ It's worth noting that not all Asgardians went extinct. There's Ran and the Vanir. You can argue the Vanir are a different race of the Asgardians, but they are the same species from the same homeworld and everything. Not sure if that will impact your answer or not. Just wanted to mention it. That said, it's a minor change. Nothing major. The point and idea is still valid. $\endgroup$ Oct 30, 2018 at 1:38
  • $\begingroup$ The SG-1 problem is also mentioned in Arthur C. Clarke's Rama Revealed book. $\endgroup$ Oct 30, 2018 at 12:01
  • $\begingroup$ Given that we can find woolly mammoth DNA from tens of thousands of years ago, it would surely not be that difficult to find some of your own DNA from a couple hundred years ago. And advanced civilizations tend to keep good records. $\endgroup$ Oct 30, 2018 at 15:24
  • $\begingroup$ On the Asguard, the final issue is that they've had to perpetuate themselves through cloning and mind transfer. But cloning causes genetic degradation over time and they were eventually unable to continue. $\endgroup$
    – jaxad0127
    Oct 31, 2018 at 2:09

Seems unlikely but a few scenarios:

1) They have genetically engineered themselves into some state where reproduction rates keep dropping until they go extinct. However, genetics in general doesn't work that way so it may be a stretch.

2) Local stellar disaster (possibly as a long-term result of them monkeying with their sun). They may be a type II civilization, but perhaps there is a reason why, although they can populate all the planets in their local system, they can't travel interstellar distances. Social reasons. Or a 'hive-mind' that doesn't allow individuals or small groups to be separated significant distances from the 'mother-brain'. Or some limit in their biochemistry that doesn't allow them to be ship-board for the time periods required for interstellar travel.

3) Religion. They are all followers of a pan-global religion or cult that necessitates them committing mass suicide at some definable and identifiable time.

4) Extermination. A much more powerful Type III civilization decides to get rid of them. They know they are being, or are about to be, targeted but have no chance against an orders of magnitude more powerful civilization.

5) Targeted disease. They may be able to cure most ills, but it is always simpler to sabotage than it is to protect, so if a suicidal terrorist group within them designed an unstoppable pathogen...

6) Boredom, social-decay. If smart AI can write better music and paint better paintings, and all of physics/chemistry/math/philosophy has been discovered, you have explored every conceivable type of planet, what is there left to do? Or, at some stage in the past they traded the ability to reproduce for 'almost' immortality...and now many millennia later they are literally bored to death with the idea of living another millennia or three.


Intentional war, an apocalypse followed by Technology Dependency failure.

We went through a nuclear race and MAD [Mutually Assured Destruction] policies, and there remains enough nuclear weapons to wipe out humanity. But you don't have to do nuclear war, per se, I'm just using that idea as an analogy.

Don't make the mistake of thinking a very advanced civilization is automatically accompanied by benign politics, or that they have stopped grasping for power, or have different parties with different ideas on how to rule, to tax, to provide their citizens freedom.

Peace is not brought by technology, as a glance at the world today should show. If anything, it can cause contention FOR the technology: people are fighting over access to expensive forms of health care and medicine that did not exist two centuries ago, but now that technology has delivered this semi-magic, people are fighting hard about how much profit we should allow to be made from it, and even without profits, who should pay for it.

Despite high technology, your civilization can have wild fights over similar advances. Who gets to be immortal, and who has to die? Why? What does the civilization owe individual members of it? Who is being (or feels they are being) exploited for others that live wonderful lives in leisure?

Find something for them to have political fights over. Religion, money, whatever.

WE are a pretty high-tech world, and are still arguing over these things. Devise a high tech world where bitter fights over religion are still rampant. And even if they reject religion, atheists like me (only 7% of the world) can still disagree vehemently over philosophical questions, like how much (if anything) we owe to society or our fellow humans, or fellow life in general, and in what form. These beliefs can range from supreme selfishness to complete devotion (to others, not God).

Then some group on the losing side, perhaps denied technology that would save their lives, decides if they lose, everybody loses, and they intentionally engineer the death and destruction of their opposition. Their plan to use war to get their way partially succeeds, but, people being people (whether aliens or not), their opposition had their own fanatics, and had used high-tech to engineer a dead-man switch. That kicks in and wipes out their opposition. Nobody wins.

Then the scattered remnants write your history, but like any high-tech civilization (including our own), they have become life-dependent on their technology which they do not fully understand, and that is not functioning after the war, and the people that could fix it are dead. They grow old and die, unable to either diagnose or cure diseases or make medicines. What % of people on Earth knows how to create a simple antibiotic, or any other medicine?

Destroy the energy and/or manufacturing base, and everybody dependent upon manufactured medicine dies when it runs out. Living spaces that depend on machinery to cool it, warm it, light it, provide oxygen and air pressure, become at least unlivable, and perhaps death traps. Sanitation and water that depend on energy for pumping and cleaning all stop, filling the streets (or something equivalent) with sewage.

The food supply, naturally segregated (like our own) into production districts (huge farms or space platforms) because sufficient power allows remote production and transportation to the consumers, also fails. Without power, the food production itself fails, uncared for, and the transport mechanisms all fail too. The population enters a phase of starvation.

The population is returned to our middle-ages or dark-ages. But it is worse: People born into that situation do not survive to adulthood without strong immune systems, and from infancy their body and mind adapts with muscle and learning to survive in a world of shortages and wants. A modern couch potato dropped into this situation just dies. Thanks to medicine, the weak immune systems and those with disabilities were not culled in childhood, and the adults are unfit, because they have not spent lives filled with physical activity, walking 20 miles a day, hunting, gathering, grinding grain, preparing food and making weapons from scratch. Like most of us in the real-life modern world, they literally don't have the muscle to survive, and even if the young do, they haven't spent a lifetime learning and practicing the skill set to survive in a world without power and technology.

Say they are unable to reproduce naturally or keep their children alive without robotic assistance and assistants, and are barely able to communicate in person. Their food may be completely processed, and the machines don't do that anymore. There is likely no "wild" area for them at all. There may be no animal or vegetable food sources for them to find anywhere, their whole environment is a machine run habitat.

Religion and politics are their apocalypse, and due to their extreme technology dependency, within a few generations post-apocalypse, they go extinct. But before the apocalypse, a few saw where they were going, and wrote about it. And during the apocalypse, before the last machines failed, they wrote about what had come to pass. And that was what was left to posterity.


In Joe Haldeman's The Forever War trilogy, humanity undergoes a transformation upon which all human bodies, across multiple star systems, are clones and share a single collective mind.

This collective being, known as Man, then gets put in its place twice:

  • In one instance another species shows them how the devices that allow for the shared mind to exist can be easily hacked and fed with false data;

  • In a reverse Deus Ex Machina, the few intelligent species discover that they are actually experiments from a god (who is actually someone from an even more technologically advanced species). This god is mad that the experiments ran out of control and even shows that they could remove the whole bloody galaxy from existence with a thought if rubbed the wrong way.

In both cases above an interstellar civilization only survived due to plot armor.

In the Discworld series of books, each planet is a disc of rock supported on the back of a cosmic turtle. It has been shown that such turtles come from cosmic eggs, which are supposed to have been laid by older turtles. Some wise men of the Disc believe that the Turtle upon which the stories take place is moving through space towards a cosmic shore, upon which it, along with many other world turtles, will reproduce. In such an event, life could be extinguished from the discs lying on the back of thousands, maybe millions of female turtles. This hypothetical apocalyptic cosmic event is called the Big Bang, and may lay waste to any interplanetary civilization that happens to have colonized only female Turtles.


There are two ways of getting to the K-II mark, one is to spread out across the galaxy and harness a noticeable percentage of the energy output of a number of stars, such civilisations would be relatively safe from local disasters. The other version of the K-II civilisation is one that stays in just one star system building either a Dyson Sphere (as a swarm, a bubble, or a shell), or a Matrioshka Brain. Stay at home K-II civilisations are vulnerable to a number of stellar scale disasters that wouldn't cause their wide spread counterparts existential issues:

  • any stellar evolution event within the primary has the potential to wipe them out, this could take the form of a supernova, or entering a cold expansion phase etc... Even a rapid succession of large flares and/or CMEs can potentially cause enough damage to cripple such a system leading to decline and eventual extinction.

  • external incidents on a stellar scale could also be lethal; Gamma Ray Bursts are little understood massive explosions that release enough hard radiation that if one were to occur within 50-100 light years it has the potential to sterilise the entire solar system. Supernovae in nearby stars could also cause lethal damage to such societies.

  • for events which people could probably see coming though it's the transient events that I think are the most realistic threats. The near transit of a heavy object like a black hole, a neutron star, or a pulsar could smash any complex orbital structure. Radiation from a pulsar or feeding black hole on its way past might be even more devastating. A rogue planet or interstellar debris cloud could also wreck large swathes of the physical infrastructure of a single system K-II civilisation.

There is a middle ground for K-II civilisations, a civilisation can be spread across a very small number of stars, harvesting a huge percentage of the energy of each, such a society could still be vulnerable to events, such as gamma ray bursts, supernovae, and transient hard radiation sources, to spite being spread across a number of star systems.

  • $\begingroup$ A K-2 civilization in a universe that doesn't have FTL and doesn't have habitable planets just waiting for someone to arrive doesn't have to be spread out to other systems; they could be confined to a single solar system, in which case they could face something such as a black hole or neutron star on a collision course. They'd know it was coming, but there'd be no way to stop it, and any attempts to try to save some of the population by speculative STL travel to other systems have a low probability of success, so they'd have to assume no one would survive. $\endgroup$ Oct 30, 2018 at 17:44
  • $\begingroup$ @KeithMorrison Taht would be the definition of a stay at home K-II civilisation yes, what's your point though? $\endgroup$
    – Ash
    Nov 11, 2018 at 11:23

Fragmentation and eventual collapse, because of evolution

The most likely root-cause of a space faring civilization's end is allopatric speciation. Basically; humanity inevitably breaks up into various different species because of the way our biology works. Then civilization (and possibly life) collapse for reasons related to the ensuing division and isolation of intelligent species.


One problem with having a population spread out across several planets that is rarely explored in science-fiction, is evolution. When meaningful gene-flow between planets stops and human populations on different planets begin turning into different species, what will happen?

The phenomena of allopatric speciation is well documented, so we can say with certainty that it will happen. We know it will happen because we know that human populations will be isolated for the following reasons:

  • The first is that space travel takes time (by our laws of physics/relativity possible a very long time), and costs financial resources so not everyone will do it. This greatly reduced migration, and gene glow. So our population's genes are mostly isolated to their own planet.

  • Second, planets are likely to be very different. Someone that is well built to survive on one planet probably isn't well suited to thrive on another. So the differences in evolutionary pressures between different planets will cause a divergence of traits. For example one planet may be hot and cause humans to adapt to heat tolerance, while another may be cold and cause humans to adapt to conserving heat. One may have low oxygen and cause humans to lower metabolic functions, and etc. This leads to humans evolving in a hundred different directions.

  • Finally, speciation is not reversible. Once speciation reaches the point where breeding between multiple population is no longer possible, there is no going back. Even if the different human species are superficially similar, they are now on a path to changing more and more from each other and can never go back. So one day these different populations will be unrecognizably different from each other.

Why does this lead to the end of a space civilization?

Species with fundamentally different needs and desires will have an inherently difficult time being part of a homogenous political entity that tries to compromise between the needs of all populations. In the end the populations can all probably govern themselves better and will know this.

So here are some ideas of what might ensue and break apart a galactic civilization:

  1. Each species fights for independence (and inevitably speciates again as they expand and then each subgroup fights for independence again, etc). Life may continue to exist, but no political entity will.

  2. War, and annihilation. Speciesism (species racism), resource wars, ideological differences, elitism, and pretty much any conflict that can arise from major differences between intelligent groups of people. Only these differences are real.

  3. Isolation. Populations become independent, lose the support of the galactic community and eventually die when a catastrophe strikes and no one helps.

All of these situations, if you add enough time to it, should happen.


I've worked with what I call the neural horizon.

It comes down to becoming more and more intelligent, and with that intelligence you start shedding the emotions you have now transcended and no need for anymore. Except it proves hard to simply choose what emotions you want to feel and which you dont. As time progresses this intelligence ceases to be angry, have sexual urges, fear injury or death, feel the need to eat or see a meaning in keeping themselves alive. They are closer to AI that sees no problem is being shut down permanently, and they let their species die out eventually.


Lone wolf super terrorist

Imagine a person who hates everything, he want to see it all gone, he also happen to be an amazing biologist with access to the top equipment of it's super civilization, so what does Nuttso Mcnuts does? he creates a virus, the virus has no ill effects on it's victims for a 100 years, it simply infects more and more (viruses like that exists in all of us).

Over a 100 years the virus spread, it may not have infected everyone but it infected over 99.9% of the population of the civilizations and then the virus internal clock runs out and it kicks in, in the span of a day 99.9% of the population dies, the other 0.1% will follow soon enough as everything they where relying on is now gone.

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    $\begingroup$ Good luck making such a clock. $\endgroup$ Oct 31, 2018 at 8:36

Escape via time jump.

In Lovecraft's The Shadow Out Of Time the Great Race hops through time, occupying bodies of civilizations they find at various places and times through the universe. The narrator encounters the Great Race as they have taken control of a race of plant beings, apparently replacing that culture completely with their own. The Great Race plans another time hop in the future, and then another - because they can project their minds through time they know how all of this will transpire.

I shivered at the mysteries the past may conceal, and trembled at the menaces the future may bring forth. What was hinted in the speech of post-human entities of the fate of mankind produced such an effect on me that I will not set it down here. After man there would be the mighty beetle civilisation, the bodies of whose members the cream of the Great Race would seize when the monstrous doom overtook the elder world. Later, as the earth’s span closed, the transferred minds would again migrate through time and space—to another stopping-place in the bodies of the bulbous vegetable entities of Mercury. But there would be races after them, clinging pathetically to the cold planet and burrowing to its horror-filled core, before the utter end.

The Great Race does not become extinct, but for someone not aware of their time-jumping abilities they would seem to do so. Their tenure in a time and place comes to an end and they disappear. The minds of these creatures then move themselves through time (only forwards, it seemed to me) and take control en masse of a different population. Their next stop will be the beetle people of Earth's future and then later another vegetable race. In his own time, the narrator finds the ruined buildings of the Great Race, their builders since departed for the beetle people.

So too your alien race. They have jumped to a different place in time with their minds and started new then/there, leaving behind their old bodies and relics of their previous civilization.


Consider HIV. Untreated it's basically 100% fatal, but it's asymptomatic during a long infection period. It caused an awful lot of deaths before we even knew of it's existence. Particularly vulnerable populations came close to being wiped out. The saving grace here is that it is pretty much a blood infection vector. (Yes, the primary vector is sexual--but most infections are due to either damage to the surfaces or to sores from other STDs. It has almost zero chance of infecting healthy, undamaged surfaces.)

Consider the common cold. It is, after all, very common. However, it's not that dangerous.

Suppose a cold virus somehow incorporated an HIV virus, but it's loosely bound and can break off in a host. Just another cold, the medical community doesn't see any particular threat. Meanwhile, HIV infects most of the world's population before anyone notices anything and when they do it's going to be awfully hard to figure out what's going on--there are an awful lot of harmless viruses floating around, it's going to take a lot to pinpoint this one as not harmless. (Remember, HIV doesn't infect anything but humans so you can't go around injecting suspect materials to see what happens.)

Once people are dropping like flies civilization gets an awful lot of holes poked in it. The immune population probably can't keep things running. The more dependent on technology they are the harder the crash (up to the point where AIs are good enough they don't need to keep it running.)

I can see such a population knowing they were doomed but having months or even years to document what happened.


They are individually not sentient, only the hive mind has sentience. While they certainly possess interstellar capability no crew is possible. To send enough of their species to another star would rip so many units out of the mind in their system that it would no longer function properly.

Their astronomers have seen the approaching body (white dwarf/neutron star/black hole, any will suffice--even a star would work but they would have an awful lot more warning time) and know it's going to hit their star but they don't have time to avert the collision, nor do they have the time to build enough lift capability to move their entire species.


This is a question I have actually heard before posed as an enigma for a campaign setting idea. A few days from present (then 2008) humanity picks up an inbound transmission form a star some 44 LY away.Humanity then spends close to 30 years decoding and analyzing this message. This gigantic message that is around 8 Petabytes of data.

When at last the message is revealed,it is video and audio showing (really as best you can) a planetary civilization. From festivals,to technology,the streets,buildings, cultural customs,examples of different language,etc. But near the end is where it gets bad. This is the part not everyone would get to see if the message went public. They had the means to leave their solar system;this is clearly shown. But for some reason they cannot leave,something is keeping them there.

As there star goes supernova (a sight witnessed close to 27 yrs prior by humanity) they cannot leave. The Enemy will not let them,it waits and watches the home world of their species die. What this enemy is was not elaborated on,only that they were feared enough that the only means this species could see of leaving a legacy was sending data dumps through space at planets they had confidence supported sentient life.

Some think they sent us this record to be remembered.others think it was a warning.

Only you can decide.


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