So, I’ve been writing a sci-fi novel that takes place a few centuries in the future. In the novels lore, it says that there was plenty of life throughout the galaxy, but humans were just contacted infrequently. Every other pre type-1 species in the galaxy (or most) had encountered alien life. Alien life was seen as true fact, and not conspiracies. But I’m still having problems with this. How could humans become more isolated than most other species plausibly, and without to much handwaving?

  • FTL Travel has been in use by many species for 700,000 years, so ancient humans were in that timeframe
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    $\begingroup$ This is a question that has been asked and theorized on countless times. Especially since you are a sci-fi writer, you must have encountered theories about this before. There is even a large and easy to find part on wikipedia about possibilities: en.wikipedia.org/wiki/… Could you perhaps comment on what standard solutions you don't want and why? Currently your question is perhaps best answered by just copy-pasting from wikipedia. $\endgroup$ – Raditz_35 Jul 16 '18 at 12:48
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    $\begingroup$ @Raditz_35: You mean like the Fermi paradox. Really doesn’t work, as it assumes that species are either few, far between, or unwilling to contact eachother, which is not the case for my question $\endgroup$ – Thunderfoot Jul 16 '18 at 12:51
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    $\begingroup$ I hate to burst your bubble here, but the Fermi Paradox is a conundrum that’s haunted physicists and anyone with a passing interest in extraterrestrial contact for close to seventy years now. There has yet to be any decent proposed solution besides the Great Filters that would account for the total absence of alien life, as any civilization roughly at or a few generations above our current tech level should’ve been able to launch fleets of self-replicating machines to explore or colonize the galaxy in less than two million years (no FTL required). The fact that we don’t see this is, well... $\endgroup$ – Z. Schroeder Jul 16 '18 at 13:06
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    $\begingroup$ Alternatively, there is the so-called “Dyson Dilemma”, which further pokes holes in the idea of advanced alien civilizations having existed in our galaxy due to the fact that we are not seeing any stars going dim prematurely, a sure sign their energy is being harvested by an alien Dyson swarm meant to harvest solar energy. You can familiarize yourself with a lot of the ideas surrounding the Fermi Paradox on Isaac Arthur’s Youtube channel, but I doubt anyone’s going to be able to give you the answer you want. Sorry. $\endgroup$ – Z. Schroeder Jul 16 '18 at 13:10
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    $\begingroup$ The major flaw of the fermi paradox is it vastly overestimates the likelihood of intelligent life evolving once life is present. That may well be the most unlikely step. Earth evolved a technological species only once in 4.5 billion years of history and has every indication of requiring a set of unlikely coincidence of events. $\endgroup$ – John Jul 16 '18 at 16:43

21 Answers 21


Okay so this is the best image I can find of where we actually are in the galaxy:

enter image description here

If most of the life in our galaxy evolved in the core and spread to the two "main" arms of the spiral (the Scutum-Centaurus and the Perseus) then there wouldn't be a lot of point looking at the relatively few stars of the Orion Spur where we have evolved. In fact to a species-centric way of thinking there's no reason to think that life, let alone civilisation, could evolve in such an impoverished setting with neighbouring stars so few and far away.


The sun and the surrounding stars were explored before the raise of earth's civilization, during some ice age or during the aftermath of the Toba catastrophe, when a bottleneck in human population made us hard to find. (Update 1: by 70,000 years ago, humans already wore clothes, and had tools and fire, and possibly a language, all of which could likely grab scientist attention, that's why I find the hard to find part important.) They found lots of ice and some life, took some samples for scientific purposes and left.

Besides, the sun's neighborhood happens to be of very little interest, with few habitable planets, not worth colonizing or harvesting/exploiting due to the long distance from the relevant civilizations. You can easily have hundreds of civilizations in the Milky Way and leave some 300 light years around us devoid of advanced life forms.

This isolation would help you partly with the explanation of Fermi's paradox (from the Earth's POV) and could also be the excuse that made our neighborhood an easy target for interstellar treaties of natural reservation, pretty much like the Antarctic Treaty: Once you go galactic, you have to start caring for natural star and planet conservation too.

Update 2: You said without too much handwaving. Someone could argue this still needs some: 700,000 years is a lot of time for people from elsewhere in the galaxy to become curious. Scientists will from time to time become interested in this little-explored corner.

An argument could be made (if you need such a level of detail) that 1) political affairs have not been always too favorable to scientists, 2) there has been lots of other interesting places to explore when possible, 3) chance has made almost every visit to Earth concur with the harshest conditions of the Current Ice Age (see figure below) and/or the Toba catastrophe, 4) you say humans were contacted infrequently, maybe there were a few episodes in these 700,000 years, but only by people who chose to actively keep the existence of humans secret or at a very low profile.

  1. In 700,000 years you could see the raise and fall of civilization after civilization, with periods when the Galaxy strives alternating with intermediate periods of war, local humanitarian crises (even the death of a star!) or reasons to make societies less interested in science, like some form of spiritual blossom.

  2. Even in relatively normal circumstances, scientists and funding are scarce—this can possibly be true also in a scenario with swarms of robots, advanced IA and stuff—and need priorities. Intelligent beings from hundreds of civilizations from tens of thousands of stars still have hundreds of billions of stars/planetary systems to explore. Unless your lore includes a technological singularity (which is optional, and somewhat boring) the targets of the most thorough exploration will either be chosen from the closest first, or in the best case at random (if travel had absolutely no costs, which I personally think is unrealistic). FTL travel does not need to be cheap.

  3. We are currently undergoing an ice age, but inside that ice age, we are in a warm sub-period. There is plenty of times during the last 400,000 years that temperatures have been 7 degrees Celsius less than today, arguably meaning less interesting climates. Most of the time it has been 4 degrees below present temperatures (see figure.) Although during this time the Earth was never completely covered by ice, a big enough ice cap could make an occasional observer with knowledge of lots of habitable worlds go "meh! Been there done that."

enter image description here Timeline of temperature during the Current/Quaternary Ice Age. Source: NOAA/Wikipedia

  1. You can still allow for some visitors intending to protect Earth's civilization from alien influence. They can study it, know about the existence of men, but keeping it for themselves while making it low profile for others as uninteresting, or highlighting other qualitites/other nearby places (like the curious case of Janus and Epimetheus, the two satellites of Saturn that periodically exchange orbits.
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    $\begingroup$ Environmental conservation was the reason used in David Brin's Uplift Universe, and it made a lot of sense. You can also pretty easily explain the lack of radio contact by pointing out that the window in which a growing civilization uses radio is very small. Once they learn how to communicate over long distances with quantum entanglement (or ansibles, or other handwavey advanced physics), there's no point in using radio $\endgroup$ – Daniel Bingham Jul 16 '18 at 20:16
  • $\begingroup$ Not sure how the Toba catastrophe is relevant - at that time, human civilisation wasn't really at a stage that would've registered as beyond 'mildly interesting' for an advanced alien species. We have since conquered most of the planet and are capable of some rudimentary space travel which would probably be enough to put us on the radar of things to watch out for in the future, but probably still not extremely remarkable in a scenario where live in our galaxy is abundant. $\endgroup$ – Cubic Jul 17 '18 at 10:25
  • $\begingroup$ @Cubic, IMHO, it could be interesting enough: by 70Kya, men already wore clothes, used fire and stone tools, and probably had a speech. If found by advanced aliens, I think it would be a very interesting natural experiment to watch such a civilization evolve, or even help it do so $\endgroup$ – Rafael Jul 17 '18 at 11:28
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    $\begingroup$ In addition, they might not come back because the Sol system barely has ANY handwavium! It doesn’t have none, as the lack would make it interesting, but there isn’t nearly enough for it to be worth mining. $\endgroup$ – Imperator Jul 17 '18 at 12:31

I'm going to give you the Star Trek inspired explanation as an actual answer, perhaps you find value in it:

One ancient alien race seeded all the other races in the galaxy because they encountered no intelligent life anywhere and felt quite lonely. They since disappeared for whatever reason. Of course they didn't spread their seed equally over the galaxy but well, within their sphere of influence. This happened to be the opposite site of the galaxy from Earth, at least far away enough.

Since then, many intelligent species emerged there over the eons. However, in the unseeded part of the galaxy, on Earth, intelligent life evolved by chance, just as it did with the ancient seeding race all those millions or even billions of years ago.

So Earth is new intelligent life, randomly evolved, while the rest of the intelligent life in the galaxy is there by design.

You can also explain more things like that. For example, the other species realized what the ancient aliens did and didn't look elsewhere in the galaxy because they knew that there was nothing seeded in our part of the galaxy. Or they just encountered no life for longe distance and never bothered to search further.

Btw, you don't need one precursor species that seeded all, you could also do a chain reaction kind of thing. Newly evolved species seeded more species.

As has been pointed out via comment by Pinion Minion: This seeding I'm talking about is one specific example for uplifting. This would also work in other variants, you could have one ancient alien race uplift other creatures with other methods. The advantage of the seeding idea is that your species don't have to be aware of it and the seeder race could be long gone, it would also explain technological differences and so on, but many variations of the idea are thinkable.

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    $\begingroup$ This would be my choice, and I'd like to add that "uplifted" species could work for this as well. Basically, the idea of uplifting is to take a naturally evolved species and give them all sapience by upgrading their reasoning, ability to communicate, and ability to use tools. If a majority of alien species have events like this in their history (either all by the same "precursor" or by previously uplifted species) the idea of a naturally evolved sapient creature could be seen as ludicrously unlikely. First contact= "I'm sorry, but you don't seem to have a rebirth certificate" ". . . huh?" $\endgroup$ – Pinion Minion Jul 16 '18 at 14:03
  • $\begingroup$ @PinionMinion That's a good point. Uplifting is more general and includes seeding. $\endgroup$ – Raditz_35 Jul 16 '18 at 14:29

This is going to be a bit of a grim answer, but a common justification for this in sci-fi is that humans are either the most violent species in the galaxy, or the only violent species in the galaxy.

We are generally not a peaceful species. We kill each other for money, or sport, or even just for being different. We have been this way for thousands of years, probably ever since we evolved, and our methods of killing have only gotten smarter and more brutal over time. We discover new technologies and our first thought is invariably how we can turn them into weapons (even here on WorldBuilding).

If aliens could watch our TV broadcasts, they'd see hundreds of depictions of them as evil invaders, hell-bent on destroying or subverting our civilisation. They'd see hundreds of glorifying depictions of heroic, muscle-bound warriors, slaughtering their enemies by the dozen. They'd see how we use "alien lizardmen" as some kind of scare-mongering conspiracy to disparage those we hate.

It's easy to assume that all aliens are as prone to violence as us, but it's also just as easy to assume that none of them are. It's entirely plausible that Earth is the galactic equivalent of that one neighbourhood that everyone knows not to go near, because if you do, you'll end up getting robbed or stabbed. Or both.

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    $\begingroup$ I'm aware of a story where most, if not all, intelligent species have the same reaction to seeing violence as humans do to eating rotten food; pure instinctual revulsion. With this as the norm, finding out that some of human's favorite past-times include full-contact sports, simulations of combat and murder, and paying actors to pretend kill each other would make aliens delay first contact as long as possible. Simply put, humans are the sociopaths of the galaxy, and that's not even counting our actual sociopaths. Apparently the book was Mind Pool by Charles Sheffield. $\endgroup$ – Pinion Minion Jul 16 '18 at 14:19
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    $\begingroup$ I feel like this explanation is becoming a little cliché already, isn't it? $\endgroup$ – John Dvorak Jul 16 '18 at 17:06
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    $\begingroup$ Attributing violence to humans is a little bit hyperbole. True, there are a lot of awful human beings, but mostly, we're not. In fact, we are the most empathetic species on this planet. We care for the elderly, weak, disabled, unwell people more than any other species. We are capable of being altruistic towards total strangers. We are known to be friendly and cooperative towards others more than most. In essence, yes we can be violent, but that's most species anyway. But we do a lot of 'nice' things most species don't. Hardly a characteristic of the most violent species in the entire galaxy. $\endgroup$ – Sach Jul 16 '18 at 18:04
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    $\begingroup$ @Sach I agree that this feel hyperbolic, but it is an interesting look at a vice that humans both demonize and revere. And I do agree that humans are likely the most altruistic of all creatures due our combination of wisdom and power, but thinking about "nicer" aliens is fun for the same reason its fun to think of aliens that are smarter than us. We are the best on Earth, but what if something was ever better, you know? $\endgroup$ – Pinion Minion Jul 16 '18 at 18:46
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    $\begingroup$ OTOH, it's unlikely that aliens are more violent than us, because then they'd surely exterminate themselves long before they manage to reach the stars. i mean, it's still unclear on which side of this line we are. by extension, it's virtually certain any advanced aliens are less violent than we are. $\endgroup$ – ths Jul 16 '18 at 22:26

Make the aliens' thinking biased.

So there are lots of alien life in the universe. They must be sharing something, be it cultural, biological, or even religious, that humans do not have. Imagine if all of your alien species, from all their differents systems, always had two brains. From their point of view, anything with one brain (or less) isn't even considered as sentient. They may aknowledge our very existence, but tagged us as "Primitive - do not bother worry about it".

Then we develop interstellar travel and all of their minds are blowing since for them, it would be like ants having learnt to build spaceships.

Another way to put it would be how they consider a planet suitable for life: "Wow, a planet with a gravity of 9,807 m/s²? Nothing can live there! No need to lose a probe for that!". Atmosphere, temperature, gravity... anything that rings your bell for your story.

And what if humans had contact in the past?

The alien scientist who came here before may have filled reports, maybe some of them have considered us sentients enough to be a part of their... intergalactic Federation, or anything equivalent.

But these reports were dismissed. Either forgotten in the mass of administrative documents, or set aside by some neglectful alien scientist, or worse, because "Humans are not relevant".

"One brain, really? Psssh!"

Humans are f****** terrifying!

Your question reminds me of a short story I read months ago, about an abducted human who is lost in the administrative process of an intergalactic civilisation - unfortunately I can't remember the name of it. At one point, the station is attacked by an arachnid-like creature that can dismember any alien there. But the human isn't even bothered and shred the arachnid to pieces like a doll. And the others aliens are now scared that humans as a species are introduced into their universe. The story has more than that, but for your story it could be enough:

  • Humans produce a combat drug when in stress,
  • Humans eat organs of other species to gain strenght,
  • It is said among the wise ones that if a human bites you, you can turn into a human yourself when the moon is full,


So maybe the aliens are aware of humans. They just don't want them to run everywhere like kids with scissors.

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    $\begingroup$ Human are seen as less of a intelligent species with thoughts and wisdom and more like those Veloraptors that figured out doors in Jurassic Park. As a professional human, I'm liking that characterization. $\endgroup$ – Pinion Minion Jul 16 '18 at 14:27
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    $\begingroup$ Humans living on a "High" gravity world is part of one of my worlds. 1/6 gravity aliens looking at humans tolerating 6, 8, 10, etc Gs is like us seeing something tolerating 36-60 Gs $\endgroup$ – Andon Jul 16 '18 at 15:29
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    $\begingroup$ They Are Made Out of Meat $\endgroup$ – SJuan76 Jul 16 '18 at 17:03
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    $\begingroup$ @RobWatts thanks, I found it! It was The Kevin Jenkins Experience. Worth reading again! $\endgroup$ – kikirex Jul 16 '18 at 18:50
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    $\begingroup$ @kikirex you should read the rest of the book as well. it's the length of multiple novels and it's still updated with a new chapter monthly. there are some chapters that seem to drag on a bit (chapter 22 in particular) but there's a lot after these chapters and the book in general is very engaging. $\endgroup$ – Dmitry Kudriavtsev Jul 17 '18 at 10:16

For one reason or another, Earth and its star have been marked as "explored and nothing is there". Since there are 100 billion more interesting, more well known places, for hundreds of thousands of years nobody has bothered to check on Earth again.

Remember the Nordic colonies in North America, such as New Sweden or Vinland? Have you ever tried sailing for the mythical islands of Antillia or Thule yourself? When's the last time you heard of anyone searching for the legendary cities of El Dorado or Iram of the Pillars?

Perhaps contact was briefly made with humans, but knowledge of humanity was buried under some greatly more important galactic event. Perhaps a couple exploration teams perished after searching a few stars, but their search was marked 'complete' in databases passed on throughout the ages. Perhaps fantastical tales have been told of lost planets like Earth for generations, but nobody takes such tales seriously enough to think Earth might actually have life.

Regardless of why, after a hundred billion stars were explored, one was bound to slip through the cracks. Earth is just a tiny island in a vast sea, and everyone thinks somebody else already landed on it.


Do we really want to make contact with meat?

According to a 1990 Omni article, Aliens don't attempt to make contact with humans because "They're made out of meat". The short story is a great read.

Similarly, due to our location, the galactic version of Google Maps routes everything around us. The lack of traffic also causes limited (or no) review on the galactic version of "Yelp!". (We also have a Bermuda Triangle reputation thanks to Area 51, etc).

The extinction of Dinosaurs has also caused the galactic version of "Field & Stream" to cease the series "Big Game on Planet Earth".

The galatic version of Wikipedia might have a decent write up. But, the more popular cousin, "The Hitchhiker's Guide to the Galaxy", only has the simplistic entry of "harmless" or "mostly harmless" (depending on updated revision).

If there was a Prime Directive, that galactic government would probably have a "no contact" ban on us until we get pulled over by the FTL Highway Patrol for not obeying local traffic laws.

Finally, according to Ancient Aliens, we are a genetic experiment. Most likely, we are an experiment that went wrong and was sanitized with a world wide flood. The area is still considered to be contaminated. The cops will bust us hard for claiming we are from a contaminated region of space.

As far as aliens detecting our radio signals from SETI, those are ignored. Citizens of the galaxy don't use light based communications to send an email to their grandmother on Omicron-Persi-8


Lets go Uplift for a moment.

Every sentient race in the known Five Galaxies was raised (uplifted) to sentience by another race. The most prestigious and well respected intelligences in the Five Galaxies can trace their lineage back to the Progenetors (and of course, the fewest generations between your race and the Progenetors, the better). This process has been going on for two billion years. A species raised to intelligence by its parent species serves a period of servitude, usually a few hundred thousand years, not that long, really.

Then Earth and Humans come along, having uplifted themselves. And not only that, they've already uplifted chimps and dolphins! Why do they get the status that comes with being an patron race without serving a period as an client race first!? The scandal!

Of course, how did Earth go without notice? Everyone wants to know...

Well, as every species in the Five Galaxies knows, inhabiting a planet and harvesting its resources and building cities there causes ecological harm to the planet, reducing its biodiversity. But in order to continue the chain of Uplift and having new and wonderous species to find, raise, Uplift and nurture...planets have to go fallow for a while, let the planet recover. Destroy all the buildings, toss it all in the ocean trenches for recycling...Come back in a few hundred million years and open it up for settlement again.

And it's a crime of the highest order to cause a species to go extinct intentionally. Surely you've heard about the Bururalli. They were given their first planet, which they proceeded to exterminate every last higher lifeform on the surface and went feral. Their parent species, the Nahalli, were made clients again for having failed to teach their client species properly.

How did Earth go without notice?

Well, it was fallow.

There was not supposed to be any contact to avoid violating the intergalactic rules regarding a planet's fallow status!


There's a lot of great answers here, but I'd like to offer one which is so subtle it might not even be interesting: random chance.

Consider the case where contact with aliens is not something that is organized in some galactic consul which makes sure all planets are accessed equally. Make it be more random. Perhaps planets get visited when it was convenient, such as when a shipping run brings you close by.

There's a fascinating story about such statistics. A teacher was teaching about statistical distributions. He gave the students a homework assignment: flip a coin 500 times, and record H or T for each one. The next day, he gathered the assignments in class, and to everyone's surprise, he graded them immediately. He started announcing whether each student cheated (by writing random letters without flipping the coin) or did the exercise properly, within a few seconds of looking at the paper. When he was done, he had divided the classes papers into two neat piles. He then asked them if anyone felt they had been graded improperly. Nobody raised their hands. He then asked if anyone knew how he did it.

When nobody raised their hands again, he explained his technique. He simply looked for 7 H in a row or 7 T in a row. If that was there, he assumed the student did it properly. If there were not, he assumed that the student cheated. We, as people, tend to assume highly unlikely events actually occur less often than they should. Sever heads or tails in a row should occur once every 128 draws, so between the two, you should expect it to occur in 500 draws at least once in the majority of cases. However, seven in a row feels "too lucky" to the human mind. We think it starts to look suspicious. Thus, none of the students who cheated let such long strings appear in their paper. They injected a H or a T to break up the streak, to make it look more random.

We could simply be nothing more than the statistically unlucky draw. We could be the one civilization that just didn't happen to get visited all that much.

Such an answer is amusing to me because that story of the teacher could appear in the novel itself, teaching people something about statistics. It also means that, when we do finally have contact (and I presume we do), the greater galactic civilization is going to have reason to treat us as an oddity. We're the statistical oddity that just got left out, and is now running to catch up.

It all depends on what story you want to write, but I find the story of humans trying to catch up to fluke accidents says a great deal about the human condition.

  • $\begingroup$ This, to me, is the best answer - may not be a great choice for a novel, but this in my opinion is very plausible. In fact, I was thinking writing a similar answer when I saw you beat me to it. One thing a lot of people forget when it comes to statistics is that improbable doesn't mean impossible. In a bell curve, there are entries in either end, albeit vastly outnumbered. From their point of view, it seems weird that they're an oddity, but in the large scale, oddities are necessary for things to average out. $\endgroup$ – Sach Jul 16 '18 at 18:13
  • $\begingroup$ A good example is lottery tickets. When you buy a lottery, the chances of you winning the jackpot is so slim you might as well not bother. Yet we have multi million dollar winners. And even that had such a little chance of happening, happened, and from the winner's POV that just looks impossible. But in the grand scheme of things, it just had to happen for things to be normal. On this occasion we just happen to be the 'unlucky' winners who never saw the little green men. $\endgroup$ – Sach Jul 16 '18 at 18:16
  • $\begingroup$ @Abigail You have a good point. I must have misremembered the story. I have adjusted the count up from 100 to 500, to make sure the story is consistent. Now I have to go find the original story and see what I messed up! $\endgroup$ – Cort Ammon Jul 17 '18 at 2:15
  • $\begingroup$ So...Anthropic principle? We're the race that didn't get contacted because "things just happen, what the hell" - Terry Pratchett $\endgroup$ – Ruadhan Jul 17 '18 at 8:37
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    $\begingroup$ @Ruadhan2300, I mean, why not. $\endgroup$ – Sach Jul 18 '18 at 16:52

The aliens are water creatures, they looked for intelligent life forms in the depth of the oceans. Clearly they didn't find many humans, there. Not alive, at least.

They sometimes found rests of ships, which they took as remnants of a lost civilization.

  • $\begingroup$ But, just because were on land doesn’t mean we’re intelligent $\endgroup$ – Thunderfoot Jul 16 '18 at 14:05
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    $\begingroup$ ...and in fact, the cephalopods we see in Earth's oceans today are all that remains of an intelligent, space-faring civilization that went extinct after launching an ill-fated colonization effort to Earth a million years ago or so. A terrible tragedy, but at least their descendants are tasty when breaded, fried and served with an appropriate sauce. $\endgroup$ – HopelessN00b Jul 16 '18 at 15:18
  • $\begingroup$ @Thunderfoot, that's why I said they didn't meet humans. I didn't say they didn't meet intelligent life forms. Dolphins might be there, before saying "so long, and thanks for all the fish" $\endgroup$ – L.Dutch - Reinstate Monica Jul 16 '18 at 15:30
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    $\begingroup$ They didn't find humans, but they found whales. And then a few million years later, they sent a probe to make contact again... $\endgroup$ – John Montgomery Jul 16 '18 at 19:35

700,000 years is not very long. It may very well be that other life forms just hasn't gotten around visiting Earth yet. And for that, there can be many reasons.

For instance, other lifeforms just may not have that much interest in visiting other worlds. They may not go exploring for the sake of exploring -- perhaps they only venture out to other worlds when they need to.

Or they have have the interest, but find it way too expensive. Or they find Earth just too far away (if you go many times the speed of light, in space, things are just very, very far away).

On the other hand, while on a galactic scale, 700,000 years isn't that long, it is long for humans. If aliens had visited Earth 20,000 years ago, how would we know? Even if they had had contact with humans; writing wasn't invented, and it may easily have gotten lost in oral tradition (after all, who would believe the person who says (s)he's visited by green men coming from a flying saucer, specially before saucers were invented?).


Multiple causes

TIME: Specifically the time where we as humans could be contacted and could record such contact. The universe is a very big place and civilizations rise and fall. In Billions of years of the existence of the universe, we have only been able to even reliably record history for about 2,000 years. Any race to contact us would have to be capable of contacting us during this windown, which compared to the age of the universe is a very tiny one. Some alien civilizations visited when the earth was still a molten ball, not even begun to cool, They come back a billion years later, then find nothing worth noting. But now their civilization is beginning to ebb, either through disease or playing with forces they did not fully understand, they go extinct.

INTEREST Some alien races are just not interested in exploring as humanity is, and are content to look no further than their own immediate interests. Perhaps they also think that they are alone, or are so advanced that all other species are of no concern. To them it would be like us trying to communicate with bacteria. Nobody would bother which brings me to:

INABILITY The life could be so alien to us that we may not even be able to perceive them. They may exist only partially in our universe, or be energy based. Their methods of communication are not only incomprehensible, but unperceivable to us.

BAD PAST EXPERIENCES WITH OTHER RACES Perhaps they had been in a long, drawn out war with a brutal race. This alien species, while having won the war and exterminated their enemy did at great cost. They do not want to go through anything like that again, so they have become xenophobic and cloak their existence from the rest of the universe.

BAD PAST EXPERIENCES WITH US It could be that initial scouts were sent to earth and were brutally murdered or just didn't like what they saw. They have quarantined this planet as dangerous and stand just outside our detection, waiting to act if we get too far out of line.


The planet was found by an alien civilization, however this civilization does not have radio signals invented, leaving their only method of communication as direct physical transfers.

However this civilization's technology, for one reason or another, does not have the capacity to enter an atmosphere this rough. (Maybe they're a civilization that has always existed on a planet without an atmosphere, or a very weak one)

So in short, they know it's there, but they can't talk to it.

  • $\begingroup$ Welcome to Worldbuilding.SE! When you get a moment, please take our tour and visit our help center to learn more about us. The inability of the vessel to get through our atmosphere was clever, but the tech to fly in space presupposes the tech to detect radio signals. Can you expand on your answer? $\endgroup$ – JBH Jul 17 '18 at 3:38
  • $\begingroup$ @JBH It only presupposes the tech to detect radio signals if you think from a limited human perspective, these are aliens we're talking about. $\endgroup$ – Callum Bradbury Jul 17 '18 at 10:44
  • $\begingroup$ @CallumBradbury, that know how to cross the vast distances of space but don't know how to pick up RF signals? I understand that they may not use the modulation we do, certainly would have trouble decoding our binary (ASCII is arbitrary), but the inability to detect the use of RF is a technology dichotomy. It's like claiming you can smelt metal without first discovering fire. $\endgroup$ – JBH Jul 17 '18 at 19:58
  • $\begingroup$ Peter, Cheers with the expanded answer. That's exactly the kind of thing we're looking for. Thanks! +1 $\endgroup$ – JBH Jul 17 '18 at 19:58
  • $\begingroup$ @JBH yeah, and maybe you can smelt metal without first discovering fire, if you don't limit the possibilities to the range of experiences expressed by humanity's technological evolution. $\endgroup$ – Callum Bradbury Jul 17 '18 at 21:38

TLDR: They don't want to influence our evolution

What does two civilization that encounter themselves do? they interact. By trading technologies or doing war, by studying the opposite culture...

We would make a huge technology leap, our culture would change a lot, in short, our society would evovle and enter a new era.

Even if they didn't offer us technologies, we would know space travel and alien are a thing.

However, if aliens have some advantages to contact us (yeah, more people will by our insert random alien thing to sell), they also have an advantage to not contact us: see how a society evolve without any help.

Yep, we are more or less an anthropological experiment. We where not put on earth by alien on purpose, but they deliberately avoid any contact to analyse how fast we evolve, and if we will be able to contact them by ourself.

  • $\begingroup$ Valid idea, but humans might be pissed when they see the cure for cancer, STDs, and flatulence sitting on the aliens' bottom bathroom selves. See if you get invited to Life Day, egotistical space-jerks. $\endgroup$ – Pinion Minion Jul 16 '18 at 14:21
  • $\begingroup$ @PinionMinion Well, humans also often oxperiment, either with animals or humans. That's how you advance science. Sometimes, sacrifying few can help lot of people. Also, that's assuming aliens will bring the cure for cancer, but they also could enslave us in holywood style $\endgroup$ – Kepotx Jul 16 '18 at 14:26

This answer depends on what aliens you use, but they could use a finicky classification system when it comes to intelligent life. For example, if the dominant species are eusocial (have multiple sexes) or reproduce asexually, maybe they simply wouldn't consider humans anymore sapient than we consider tool-using birds sapient. Its very arrogant, but it would mean they have no reason to socialize with us as long as we stay on Earth.

Alternatively, you could so say that Earth and the local group has already be claimed by a very territorial alien species. This species wouldn't be interested in interfering with humans either because Earth doesn't have any resources you couldn't get elsewhere for cheaper. Maybe they don't want any interaction with Earthlings because they are worried it would forces changes in their culture, so they ignore the human problem until humans leave Earth themselves. In the meantime, the territorial species discourages all the other aliens from going to Earth. Maybe once humans make first contact, the whole galaxy gets pissed at the humans "landlords" for never doing anything. Could make for a fun backstory, I don't know.


We are in the waiting line to be contacted, you could always assume the galaxy is extremely populated, but only one or two species have got so far as to be able to travel faster than light. The ships are rare and there are millions of planets calling out for a visit and each one needs scanning and observing and processing before being allowed into the club.

we are just waiting for our turn without even knowing


Simple: Humans are just a backwards species that is far more violent and short-sighted than their alien brothers. A culture that puts people in giant stadiums and makes them fight to the death? Too violent, let's wait a bit before contact... A culture of xenophobia that murders entire groups of people and calls it their "final solution"? Too dangerous. A culture that treats their entire planet as a waste disposal plant? I guess the humans really don't improve. Let's see what the future holds!

calvin and hobbes


Man (AKA Homo Sapiens) is the most violent animal on this planet. I suspect that the dark side of the moon has a large warning sign (or transmission device) to warn intelligent species that there is nothing of value on the adjacent planet.

Perhaps a few thousand years in the future, assuming mankind has not eliminated itself and that the radioactive debris reaches acceptable levels, something might get curious as to what was here.

In fact, I am quite surprised that I am alive today as I never expected to live past middle age due to what would have been called World War III. I worked in industry in some interesting places, including within the program office for the development of the Poseidon submarine launched ballistic missile. I reported directly to the Chief of Weapon Systems Effectiveness.

It is fortunate that Russia was sufficiently intelligent to recognize that World War III would not be of benefit. I do not have that degree of confidence when I look at some countries that currently exist in the Middle East and Asia.

  • $\begingroup$ Hello, Sidewinder, and welcome to Worldbuilding! Please take our tour and visit the help center to learn more about the site. Have a nice day! $\endgroup$ – Gryphon Jul 17 '18 at 2:09

Only about 0.0000000000000000000042 percent of the universe contains any matter. We are only a very, very small fraction of that and on top of that, we are also in a fairly sparse region albeit the Milky Way and Andromeda are beacons seen many light years away.

So, it is as it happens that we were just not stumbled upon. Our inhabited planet was not marked on any galactic maps. We are lonely of visitors.


Faster-than-light doesn't work here

For some reason, the usual faster-than-light travel devices don't work in (and some light-years around) our solar system. Due to this, none of the spacefaring species discover us here.

In Beyond the Impossible, this is caused by a device from some ancient civilization (older than the current rulers of the Galaxy) hidden on Earth, but it could also be some natural anomaly.

  • $\begingroup$ Hello, Paŭlo Ebermann, and welcome to Worldbuilding.SE! Please take our tour and visit the help center to learn more about the site. Have a nice day! $\endgroup$ – Gryphon Jul 17 '18 at 18:37

They did

They did. Millennias ago an ancient species, the First, discovered the solar system and built bases on Earth, Mars and Phaeton.


Some architectural wonders like the pyramids of Giza or Machu Picchu are remnants of their presence. Look it up, there are many sceptics around the current explanations of the construction and use of these ancient sites. I can recommend YouTube channel Bright Insight, whose host questions a lot but does not throw in wild theories like others do. Should provide a lot of inspiration that fits nicely into our storyline. Why the bases on other planets? Earth itself proved to be inhospitable to the species itself because of temperature, atmosphere or seasonal climate changes - make something up, I'm not going into the Firsts' physiology and biology - so they settled on Mars to provide food and shelter for the scientists and collected minerals and metals from the resource rich Phaeton.

The Homo Sapiens project

Discovering various primitive Homo species they started genetic alterations of the most promising species trying to create a simple, yet effective race to act as soldiers, which resulted in the creation of Homo Sapiens. There were many issues of the soldiers' obstinacy, denying orders, going rampant killing other soldiers, birth issues (humans are pretty much the only species with such a high stillbirth rate and danger of the mother dying in the process) and various other health problems. An explanation to our hostility.

Galactic war

The Homo Sapiens project has still been in the process when another rivalling species, the Second, declared war on the First and in the process drove the solar system into a battlefield, destroying Phaeton altogether ripping it apart into small chunks forming the asteroid belt between Jupiter and Mars, stripping Mars of its atmosphere casting it into the lifeless planet it is today and causing destruction to the bases on Earth.

Forgotten history

Few humans were able to evade the destruction and remained undetected by the galactic fleets that were busy fighting each other and over millenias the history of the First cast them into gods, changing the actual events into our current religions. The biblical myth of the great flood - one of the Seconds' superweapons - still lives on today (other religions have told this story before in different ways, like the ancient Sumerian belief) that was part of the devastating destruction.

Neither the First nor the Second ever returned, with the destruction of Mars and Phaeton driving the Solar System due to its distance and empty neighbourhood into irrelevance and the Homo Sapiens project being cancelled due to the high amount of investment with highly problematic and seemingly unsolvable physical and mental issues. There was no reason to return.

  • $\begingroup$ It's a nice answer, but this doesn't really answer the question in any way. $\endgroup$ – Sydney Sleeper Jul 17 '18 at 4:22
  • $\begingroup$ Sure it does, in a way. Modern humans with our current history weren't discovered because the alien races didn't have a reason to return after the destruction that happened. They simply never scanned the region anymore. $\endgroup$ – Otto Abnormalverbraucher Jul 17 '18 at 7:59
  • $\begingroup$ 2 downvotes, although it does explain, why humans were more isolated than other species and there is no clear contact written in our history books, which was the question. Yeah, thanks. $\endgroup$ – Otto Abnormalverbraucher Jul 17 '18 at 8:05

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