Basically, why are aliens always jerks that want to roflstomp us with a military doctrine borrowed straight from the colonial era as written by Hitler and co-authored by Darth Vader? What possible reason could there be for a more advanced species to want to destroy us? Are they simply dogmatic and xenophobic? Do they see other races as an unnecessary drain on the universe's limited resources? Are they afraid that we'll become a possible competitor race if they don't destroy us now? If so, how did they get to be so advanced with such a hostile approach to cooperation with other sentient life? Why would we be a drain on resources when, at a certain point in every species' technological development, scarcity should climb asymptotically close to zero? If they're so much more advanced than us already, why would they even perceive us as a threat?

In a nutshell, my question is, "what motivation could there be for an alien species to be intentionally malevolent towards us rather than simply destroying us as an unintentional side effect of doing whatever it is they do?"

  • $\begingroup$ Less advanced species in general or "us humans"? Your title says one thing but your nutshell says other ^^U $\endgroup$
    – xDaizu
    Feb 6, 2017 at 16:01
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    $\begingroup$ What differentiates a good answer from a bad answer? I see this either as a socio-cultural thing (which would be species-based, and thus too-broad unless you define your species) or intent on telling the best or most plausible story (which would be story-based or opinion-based). $\endgroup$
    – Frostfyre
    Feb 6, 2017 at 16:05
  • $\begingroup$ Your title implies a general reasoning for a new story. Your question seems to focus on stories already written/asking for some insight into the minds of aliens we know nothing about. Do you have a story in mind? Any setting to help us narrow down the answers with? $\endgroup$ Feb 6, 2017 at 18:32
  • $\begingroup$ Issac Arthur's youtube channel delves deep into concepts like this, related sci-fi trove we've been taught, and how realistic each are to actually occurring. "Crazy Aliens" has a lot of what you're looking for, and after check out "First Contact" or "Fermi Paradox". His stuff gets pretty broad, much like your question. :) $\endgroup$
    – IT Bear
    Feb 6, 2017 at 21:21

9 Answers 9


the "side effect" clause rules out terraforming, resource acquisition, etc. motivations which are relatively common in Sci Fi.

I've seen several theories used in various sources.

  1. Preemptive strike. The aliens have observed how well we get along. They have observed our rise in technology. They extrapolate that once we figure out FTL and/or their existence, they realize we're a serious threat to their existence. I've read some sources that say if there's even a possibility that a high-tech civilization might eventually become a threat, then as a matter of survival, you have no choice but to strike first before they discover you and could potentially preemptively strike you instead.
  2. Plague Perhaps our planet/species carries some... thing... that is infectious to them.
  3. Xenophobia Unlike my 1 above, maybe they just hate things that aren't them. See wasps and other violently aggressive species on earth and extrapolate up.
  4. Diplomatic ineptitude perhaps at an early encounter, we do something so completely taboo to their society that it sparks a war. Perhaps we insult their gods, or their racial identity, or their mothers. Or we show them our teeth in what we think is a pleasant smile, but they see it as an aggressive show of dominance. Or the first time we use our nifty translator software, it starts spewing racial insults... you get the idea.
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    $\begingroup$ Perhaps we ARE the plague. $\endgroup$ Feb 6, 2017 at 16:16
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    $\begingroup$ The extrapolation from my point 1 is that, the second you become aware of Aliens, you must attack immediately, with all possible power. Anything else might mean the end of your species. Scary to contemplate, but our species tends to think along those lines... $\endgroup$
    – CaM
    Feb 6, 2017 at 16:21
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    $\begingroup$ Honestly it is the only rational choice. Once you go to the galactic scale, things are just incredibly dangerous. Strap a FTL on a ship and ram it into a planet and that planet is now dead. It is just too easy and too difficult to defend against. It gets much easier if there is some sort of Federation or Galactic Collective to step in, but the actual First Contact and formation are all but impossible. $\endgroup$ Feb 6, 2017 at 16:24
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    $\begingroup$ @CM_Dayton, in Starship Troopers such strategy was used against Earth, and not only the movie, but the book points it too. To be honest, we were really bad guys in the book, fighting not only the bugs, but another species too. $\endgroup$
    – mr4eshir
    Feb 6, 2017 at 16:39
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    $\begingroup$ @user2259716 I always hesitate when I see someone say something is the "only" rational option. It might be true occasionally, but... Well, there's a lot of situations where it's really "the only rational option I've thought of so far, and since I'm pretty sure it's the only option, I've stopped looking for alternatives." $\endgroup$
    – user867
    Feb 6, 2017 at 21:00

If so, how did they get to be so advanced with such a hostile approach to cooperation with other sentient life?

Sorry, but what does the one have to do with the other?

I assume you mean "technogically advanced". To posit that cultural tolerance of other species (particularly species which are not even remotely related biologically) is required to develop a high technology is naive in the extreme. Even within our own history, the belief that a culture's efforts can be dismissed as doomed to failure because of some feature we don't like has lead to major misjudgements. I give you, for instance, the Russian space effort and the Japanese electronics dominance. In both cases Americans often dismissed their efforts due to cultural judgements, and were shown to be spectacularly wrong.

And that's restricting the analysis to humans. The thing about aliens is that they are alien. Their motivations and interactions do not have mimic our own, so there is no reason to accept your basic premises.


Aliens are jerks.

No all of the aliens, of course. Just the ones that want to destroy us.

Perhaps the aliens come from a post-scarcity civilization, where everyone has the energy equivalent of a few Dyson spheres at their disposal. For the most part, the aliens are happy to build their own palaces, research arcane maths, and generally enjoy themselves. They pursue whatever makes them happy, so long as that pursuit doesn't cause injury to their fellow aliens.

However, not all of the aliens have benign interests. Some individuals, just like the kid with the magnifying glass torching a line of ants, take pleasure in watching lesser beings burn. They use their energy allowances to build interstellar fleets to go off and subjugate lesser races. Not because the lesser races are a threat, or because they're particularly delicious or anything. The aliens are so far beyond us and have so much raw power at their disposal that we couldn't possibly threaten them, and they could easily engineer far tastier food.

No, the individuals that attack us do so out of sheer spite and malice. They enjoy watching us suffer, so they devote their energy to making us do so. Jerks.

  • $\begingroup$ That is the Alien Commandant line to the human hero "you don't care about ants, why should I care about humans?" - logical fallacy spotted: If ants could communicate, things would be a bit different. $\endgroup$ Feb 6, 2017 at 18:41
  • $\begingroup$ @Mindwin Ants can communicate. Humans just think the things they communicate about just aren't of any interest (except for the people who actually study them) $\endgroup$
    – Rick
    Feb 6, 2017 at 19:10
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    $\begingroup$ @Rick "The only hope for our world is to contact an alien entomologist!" $\endgroup$
    – user867
    Feb 6, 2017 at 21:03
  • $\begingroup$ @Mindwin If ants could communicate in a way that was intelligible and relevant to humans, there would still be people who would take joy in burning them up. $\endgroup$
    – ckersch
    Feb 7, 2017 at 16:53
  • $\begingroup$ @ckersch but it would be outlawed and "ant rights" would come into play. In a few years, killing ants would be close to homicide. $\endgroup$ Feb 7, 2017 at 17:32

The short answer to this is that most entertainment writers are American, and simply reflecting the zeitgeist of the times. America has overthrown more civilizations than any other empire in history, see https://williamblum.org/essays/read/overthrowing-other-peoples-governments-the-master-list for post WWII alone.

The second answer is Conflict drives Story. Without a malevolent alien race, there's no conflict, so the story is weak. Simple minds appreciate Manichean black & white cardboard characters, so since we must be Good, the invading aliens must be Bad.

Taking the question literally, primary known motivations for blowing the heck out of cockroaches, deer, Palestinians, or Syrian civilians, include: sadism; entertainment; sport/competition; narcissism; the perceived need to exterminate vermin; coveting and stealing natural resources; food; strategic competition; domination; punishment, for perceived or imagined sins; to generate employment; because someone else wants them gone; culling the herd, or "cutting the grass"; because the superior civilization is convinced it has been victimized; machismo; alien politics; to build a bypass; because you might hypothetically one day want to build a bomb, and thereby threaten the civilization that actually has bombs; the ever-popular Right To Protect (Right To Slaughter); to teach you a lesson; or because you happen to be in the way of settlement expansion.


Experience. Letting other species live and get too advanced always ends badly.

This species of alien is extremely long lived and are psychologically very unusual vs most evolved organisms.

From their point of view letting humans live would amount to foolishly ignoring their experience from the last 100 times someone has developed hyperspace technology.

It's always the same

"First they figure out how to get to other stars, they talk a big game about peace and prosperity and cooperation but within a few generations someone somewhere in their species little empire eventually decides that it would be a good idea to strap a blob of grey goo to the hood of a von neuman probe and strap that to a hyper-drive."

"Sometimes it happens quickly, sometimes it takes until the species has some stupid internal war. Sometimes it's some twisted attempt at conquest, sometimes it's misguided curiosity from someone who thinks they can map the universe with self replicators, sometimes one of them creates a badly made AI with too much brains and too little sense but it always happens."

"The last time half a galaxy had to be quarantined, cut off from hyperspace for half a million years(not trivial even for us) sterilized system by system and that was after every living thing there was turned into nanite sludge."

"We like a universe that has more than one species. We like diversity. We like a universe that isn't being turned into a trillion trillion copies of members of your species in some kind of VR masturbation fantasy."

"We want a universe where it's possible that other species will one day arise after you but we know that if we look away for even a few thousand years you'll have wiped out half the galaxy."

"So you have to die. You have the option of giving up all technology beyond what you'd call the 17th century and sticking to your own planet but I can see you're not keen on that. Yes, with your current population that would mean billions of deaths for the first couple of generations."

The Cull

"To enforce this a troupe of volunteers will be arriving at your planet soon. Why don't they have weapons capable of wiping your very planet from reality? For about the same reason human hunters don't perform deer culls with nuclear weapons. It's unfair, unsporting and would leave the planet unusable for any species after you."

"Their job is to either wipe out humans or to destroy your scientific and industrial base to the point where you'll be unable to maintain your current technological civilization."


We were once a young race, full of both hope and life. Our society rose ever higher on the backs of our scientists, but we rose too high. In our folly we sought to become gods, to conquer the very secret of life itself. Fools! We brought the Collective into being, a twisted mockery of life made of machine. Long we fought, until our home was no more. We ran, until we could run no more. And by chance found a new people. They were like us, made in the same image, doomed to make the same mistakes. So we took pity on them, we destroyed them so that they may never know the same despair as we. We brought monsters to life, only for them to consume it.

So a twisted sort of logic, but in this instance they created grey goo and doomed the universe. And their mercy is to snuff out life before it has the chance to experience the shame and despair they do. While they are in their prime, so to speak.

In a less poetic universe, you could say they fear the consequences of unrestrained science and either step in to guide a civilization down the path they set, or destroy them. If civilizations always stray or the consequences are too severe it would make sense to just kill them all.

TLDR: Blackholes, FTL, AI, Nanities, and Dark Matter can reaaallly fuck things up.

  • $\begingroup$ Is the first paragraph a quote regarding the Borg's creation? $\endgroup$
    – mkinson
    Feb 6, 2017 at 18:49
  • $\begingroup$ @mkinson No, not intentionally at least. There have been many various nanite / ai collectives. I tried to use a generic name. I think Collective has been used by many universes. $\endgroup$ Feb 6, 2017 at 19:40

There are numerous of reasons.
Xenophobia (and other -phobia included) - is a prime reason, no mater humanoids they are or not, xenophobia is the thing. As an example - xenophobia have it's own between human races, in animal life, etc. Now, imagine a first contact with inteligent arachnoid race where captain has arachonophobia. My bet - the captain will not even consider the race inteligent, and kill it with fire.
Hunt interest, favorite meal - as was shown in Predator and War of the Worlds (the book) - we could be a good meat, or a nice trophy. And we don't even need to show how inteligent we are, Predator race was well informed we had infrastructure and even space program.
Envy - yep, we can have something which other don't, again, War of the World, we just had warmer planet (and tasty blood, but warm planet too). in Battlefield: Earth - gold.
For science - we are, or our dear planet is, a subject for scientific experiment. Don't remember any examples, but there should be more than one, for sure.
Old rights - as it were many times, many wars were started on the basis of real or fabricated claims for territory.
Business - money (or material) says it all. Again, our own history has examples, where business interest bring violation to the place, at least USA has one to it with Gold and Oil rushes. And Ferengi RoA 34.
Burocratism - DON'T PANIC.
Added one: Old Data - while aliens are far away from our solar system, the light reflected from our planet has some troubles reaching them. And all they see, at best, the events 4 years ago (Alpha Centauri), more distant races may not see even this century. So, imagine very distant race found very nice place to live, had a lot of troubles to reach it, and... It's wasted! Polluted and overly-populated with aborigens! They look at it, don't know, a century ago, and it only had a nice green flora and some cute large lizards, and now...


Don't forget the Hitchhiker's Guide to the Galaxy (Douglas Adams). We could just be in the way of a new intergalactic freeway

  • $\begingroup$ I thought @DragonLord had covered that? $\endgroup$
    – LSerni
    Feb 6, 2017 at 20:15

The life form we know here is very specifically tied to our planet and the scope of life as we defined it is very limited. Life for us is carbon-based, DNA like structure, with limited chemical interaction. But the universe is more diverse than just that we know. Imagine life form based on anti-matter or another assembly of sub-particle we don't know yet. Things like neutron star are extremely dangerous to us, there is a possibility that our simple existence might represent a threat to them if we ever approach them in any remote way.


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