I'm building a world but I keep coming across the idea of putting an ancient race in the mix similar to that in the mass effect or halo story lines. However, I feel like it has been over used lately. It really makes my story more believable but I think it takes away from the story at the same time by making it seem less original if that makes sense.

Without getting into a lot of detail, several different sentient species develop simultaneously on different planets in a solar system with planets that are in very close proximity to one another and most of the story takes place when the other races discover one another.

If you read this far you might understand part of my dilemma because of how improbable this story sounds. Without creating a back story of an advanced alien race that basically manipulated the solar system to this are there other probable explanations?

  • $\begingroup$ When you say they discover one another, you do realize they'll discover evidence of them with telescopes YEARS before they're able to even communicate with, let alone travel to, them, right? Also, where exactly are these planets? Are they in the same orbit, just a different spots? This is extremely, extremely unlikely to occur and remain stable. $\endgroup$
    – iAdjunct
    Feb 24, 2017 at 4:14
  • $\begingroup$ Yes I realize that they will know of each other's existence long before they actually meet. The planets are in different orbits around a smaller star so that they can be closer to one another and yet still remain in the habitable zone as well as make it plausible that say three or possibly four planets to be earth-like. The solar system itself is not in question rather possible scenarios that might cause sentient life to form if that makes any more sense lol $\endgroup$
    – Dtb49
    Feb 24, 2017 at 4:34
  • 1
    $\begingroup$ From a story point of view, you don't have to explain it. Within the story it could be acknowledged that no one really knows why their star system ended up like that. Allow for the truth, whatever it is, to come out later. $\endgroup$ Feb 24, 2017 at 5:42
  • 1
    $\begingroup$ Dtb, welcome to the site. Can you update your question to define what would make one option better than another? As it currently stands your questions does not have any criteria that would make one answer better/worse than another. $\endgroup$
    – James
    Feb 24, 2017 at 14:45
  • 1
    $\begingroup$ Why does it seem unlikely that similar planets will not form life at similar times? We already know that natural selection can produce similar structures in unrelated evolutionary branches. $\endgroup$
    – user458
    Feb 24, 2017 at 16:34

12 Answers 12


It's actually not completely improbable. There are meteorites on Earth that originated on Mars, and it's possible that there are others which originated from Mercury or Venus which haven't been identified as such yet due to lack of comparison data.

It has also been hypothesized that microbes could "hitch a ride" between planets on meteorites. Similar reasoning is why NASA crashes its Saturn and Jupiter probes into their planets at the end of their missions -- they don't want to risk contaminating one of their moons accidentally.

So it's not unreasonable to imagine the following scenario:

  1. Primitive life evolves on one of the more central planets fairly early in the development of the planetary system.
  2. One or more impactors on the life-bearing planet scatter microbe-bearing meteorites into interplanetary space.
  3. Some of these meteorites land on other planets in the system.
  4. A small number of microbes survive the journey and begin evolving on their new home planets.
  5. Due to circumstances, evolution progresses at roughly the same pace on each planet, resulting in them each bearing at least one sentient species at a given point in time (e.g. when the story takes place).

The last point isn't actually unreasonable. Depending on how you measure sentience, Earth currently has quite a few sentient or near-sentient species: primates, corvids, cetaceans, octopi, etc. Early ancestors of humanity have been around for hundreds of thousands if not millions of years, and its possible that our descendants or the descendants of one of the other sentient species on this planet will continue to exist for millions of years to come.

  • 1
    $\begingroup$ I like point 5. I think the trick to making that work is to have a point in the evolutionary process which "catches" species before they get intelligent by making it evolutionarily undesirable to take the next step. Then, if a cosmic-scale event were to break down those barriers, the race for intelligence could start at an even starting point. $\endgroup$
    – Cort Ammon
    Feb 24, 2017 at 23:58
  • $\begingroup$ This is covered in the question Is it statistically and physically possible to have two civilizations in the same star system? $\endgroup$
    – JDługosz
    Feb 26, 2017 at 9:09

Colonization -> Dark Age

This is another well worn trope, e.g. Vulcans and Romulans from Star Trek, but the alternative is that a group from planet A colonized some of the other planets, but then the civilization collapsed on the initial planet. The big advantage of this trope is that all the civilizations have the same development starting point only a few centuries in the past, which makes becoming aware of each other at the same time much more probable.

I don't think this is as implausible these days as it seemed many years ago when the trope surfaced. First off, you only have to look at our own space program on Earth. Did you know that the last man on the moon walked there Dec 1972? That is now 44 years ago. For reference that 44 year gap is the same between the Wright brothers and the first supersonic flight by Chuck Yeager.

Second off, the mechanism by which civilization wounds itself has become clear. Climate change going over a tipping point of some sort, while I consider it pretty improbable in reality, makes a great storyline. You don't have to destroy civilization on the first planet at all to set it back a century or two. The concept of migrant hordes from the poorer tropical regions flooding the more advanced parts of the world is more or less a reality. If you consider the current migrant problem in Europe was caused by a war in a country of 25 million, what would happen to 1.3 billion Indians if the monsoon failed? It is easy to imagine a situation r where wars over limited space consume the planet. Maybe sprinkle a few nukes in for good measure.

A last story aspect that has come up on this site a lot recently is Kessler Syndrome. A Kessler catastrophe around the home planet could put space exploration back by centuries if it was catastrophic enough, not just from making space launches hard/impossible, but by politically convincing the people of the home world to abandon space.

As for the colony worlds, they could lose contact with other worlds through low population and lack of expertise. Imagine a colony of 1000 that is focused on farming and terraforming. The knowledge of how radios work could be lost in a generation if there were no radio/electrical engineers around in the first place. Cut them off from the main planet, have them focus on survival and a few centuries could turn the home world into a half-remembered myth.

Put some of these things together, and it is not too hard to imagine a 200 year or more gap between colonization and the re-entry of some of these worlds into space. That might get you what you want. You could have situations where several colony worlds make it into space together to find the ruins of the homeworld, or the homeworld remembers the colonies but has ignored them and space for centuries.

  • 1
    $\begingroup$ I like your idea very much, but I would add one more thing. Before "the collapse" the specie should develop designer babies. That would explain how the hell quite big genetic differences appeared so rapidly. Actually in such situation rubber forehead aliens that can reproduce with each other suddenly make sense. $\endgroup$
    – Shadow1024
    Feb 25, 2017 at 19:27

Space/Time Rifts

No need for an alien race.

Assume only one inhabited planet to start (a variant would be multiple, but to keep it simple, assume one for now).

Have a rift "Event" in space/time appear on that planet in different locations on that planet --- with the other side of the rift being the other planets you desire to populate.

Then, some of the inhabitants from those various locations go through (or are shifted through - perhaps an entire city gets scooped up and moved) and end up on these other planets.

They will have been roughly equal developmentwise before the "Event" and being shifted to their new home worlds. But, their new home worlds could alter them genetically and technically and perhaps morally.

When they meet for the first time, they may have some common race memories which could make for some interesting interactions, but, they will also have developed so far away from each other over tmie that they are essentially alien to each other.


Ancient Forerunner Race Solutions...

  • Your entire solar system is an abandoned zoo full of species from across the galaxy.
  • Your entire solar system is a homework assignment or thesis by an ancient student of biological adaptation to planetary conditions.
  • Your entire solar system is a Casa Blanca style safe zone for refugees in a galaxy scale war between two ancient alien races.

Solutions without a Ancient Forerunner Alien Race

  • Your own species once colonized the entire solar system, using genetic manipulation to adapt some of your kind to each of the planet's environments. That advanced, space faring civilization then collapsed leaving each planet to evolve independently.
  • A flaw in your specie's genetics has caused widespread dementia and xenophobia through your population. The other planets are all actually lifeless, but everyone sees aliens everywhere they look.
  • Virtual Reality! Yep, each planet is populated by a separate city's best VR players and they are all competing in an immersive delusion which utilizes memory altering drugs to convince the players that the simulation is real.
  • And my favorite... It just happened (because God has a sense of humor and likes watching His creations fight)

New Ideas after reading @SRM's excellent answer...

  • An enormous herd of a non-sentient space-born predator species floats into your solar system and some fly down onto all of your planets to become the apex predator on each world. On most of the worlds, a sentient species evolves to wipe out the invaders. On one of the worlds, no indigenous species arises, so the invaders thrived and eventually evolved sentience as well.

Multiple species all "coming of age" at the same time is, most of us agree, improbable. You need to tie the emergence of sentience to an environmental trigger. That's what gives the "ancient seeder species" idea such power.

So.., what other environment triggers are there that would affect multiple star systems? Well, pretty much only one comes to mind : a local nova. The ejecta of a star exploding would impact other systems. Let's assume that life is common on worlds -- an open question and still a plausible theory, despite the counterexample of our own solar system so far. Life is on all these worlds. Then the nova disrupts the ecology by causing a major extinction event and making the environment more chaotic for an extended period of time. We don't know what triggers sentience, but a world where survival demands problem solving would select for it.

So you have your worlds equidistant from a nova and you posit that this opened the door to sentient dominance, all at the same time. And you argue that the laws of nature are structured enough that once sentience happens, the path to space flight is, in general, a straight path with a fairly fixed timeline, give or take 10k years. Sprinkle your worlds with a few species that are slightly slower to develop. You'd pass plausibility for me and, I suspect, other readers.


How "hard science" is your story? What is the tone? There are many pulp sci-fi stories with this basic concept. Parallel development and equivalent analogous technologies is a pretty basic trope, so it doesn't really need a lot of explanation so long as you are not trying to be a hard science author.

The primary reason for an "ancient race", IMHO, is so there can be advanced tech artifacts lying around for the current populations to use but not really understand. Things like stargates. It lets you handwave stuff but still keep within a "Sci-fi" setting. It can also explain why Martians are just red skinned bikini clad babes (i.e. they are just transplanted humans) but E.R. Burroughs didn't even need that!

Humans currently assume that technologic advancement is always forward and rapid, but we forget the thousands of years on earth when very little happened. So if you need a somewhat plausible rationale for simultaneous tech advancement across an entire solar system, perhaps your solar system went through a dense nebula that resulted in lots of orbital micro-bombardments and reduced solar input, so life got real hard on all the planets, effectively halting civilization for a few million years or so. But this allowed primitive life to all reach a similar sentient, pre-technological level. Then the solar system leaves the nebula and suddenly there is lots of sun light and rocks aren't falling every few years. So every planet is primed for a technological renaissance at around the same time as each planets version of Neanderthal kicks into high gear with agriculture and technology (look at all this metal ore just lying around!!). Bam, each planet is basically developing simultaneously and you can fudge it a bit so they all have fairly equivalent technological achievements.


What do you mean "developed" at the same time? Humans "developed" 2 million years ago, and modern humans 200,000 years ago. Human civilizations developed 10,000 years ago and modern tech levels developed less than 100 years ago. There are also falls such as the fall of Rome and the dark ages at the end of the copper age. There are civilizations that rise and fall due to others and some that do so due to their own stupidity.

My guess is "how do you explain several close species developing star travel and roughly equal levels of tech at the same time?" Well Let's say they all developed within the last 200,000 years and are all within a 50 light years radius. At some point in those 200,000 years they all get to the point of writing, farming, etc... What does that mean in terms of today's tech? Nothing. Is it surprising giving 200,000 years? nope.

Ok so some time after that point they reach the iron age.... How does that effect their technology as you'd see it? What exactly does that mean for history? Not much, because Greece, Rome, the Middle Ages, all exist within the same area of technology. Even science and the renaissance isn't going to matter much about when it happens. pre 1900s technology could go on for centuries, perhaps millennia and it wouldn't be surprising...

It is only the Bessemer Process that really makes things start moving forward to the point where multiple civilizations of the same type at the same level likely won't exist in the same time frame. Well I sorta lied. A civilization that has the Bessemer process just makes expanding easier due to lots and lots of high quality steel. This allows civilizations to build large and build crazy contraptions like Plains, Trains, and Automobiles... as well as the eventual LHC, but ultimately this just means that the civilization can get up to the point of a global to solar system based civilization, but the next stage after this, for all we know could take millions of years which makes similar civilizations more and more likely. Sure they'll be at different levels of converting their solar system into multiple colonies, but ultimately they'll be at pretty much the same level.

That's right, we're pretty much at a possible zenith that could stand for the rest of history, and there is nothing that says we'll decided to convert all matter in the solar system to habitats or just leave them as they are and live in harmony with nature more so. So you could have a species that has reached the same zenith who really have developed out the rest of their system or really young who have. They're both going to be roughly equivalent to each other at this point.

Now the question is how do they all get triggered to look out to interstellar space at the same time... Well, what if they are all older than "Earth" and all realized radio waves were useless long ago and while they have developed superior communication techniques that are similar to radio waves, because radio was such a waste of time each of their civilizations all gave up and never tried with the better stuff and they all just happened to have those time frames of people looking and emitting radio waves were just out of sync, but then "Earth" happens upon that superior communications tech and they're all roughly x distance away from "Earth" and so everyone in that area get the same "OMG SOMEONE ELSE IS OUT THERE?!" at the same time and thus begin working on interstellar technologies all at the same time.

Thus you have all the species both developed in the important areas at the same time, differences, and no "ancient alien"

Oh! and BTW, the ancient alien thing doesn't really work, because of what I described above. If 2 species start at the same point it doesn't mean they'll get to the same point at the same time. Rome could have survived without the burning of Alexandria and humans could have been in space 2000 years earlier. Or Persians could have won against the Greeks and Humans may never have even reached the moon due to the change of western philosophy.


Assuming a planetary system with multiple planets in its goldilocks zone, just like TRAPPIST-1, then while is extremely improbable that several sapient species could all make contact with each other effectively simultaneously, it's not impossible.

What people often fail to realize is that low probability events happen all the time. Even having an ancient advanced sapient civilization jury rig a planetary system's multiple habitable planets to have sapient species emerge effectively simultaneously would be itself a highly improbable event. Unless the advance ancients are doing this on a regular basis.

An alternative solution to sheer improbability becoming a reality and advanced ancients is that a sapient species arises on one of the habitable planets. They expand into interplanetary space, conduct genetic engineering on the native lifeforms, their home planet succumbs to an apocalyptic catastrophe and the colonists return but their civilization regresses into barbarism, all memory of the space-faring phase of their civilization is lost. By the time it re-emerges the other planets have spawned their own civilizations. This is a local uplift scenario involving not quite advanced ancients but then removes them from the scene.


Modern race

Instead of an ancient founders' race, what about a modern race? Openly acting they'd be gods, which may not fit with your story. But what if a race was acting behind the scenes?

For example, there was a story called Waiting for the Galactic Bus. Two brothers are stranded on Earth in prehuman times. Since they were bored, they made a few genetic changes to some apes to make them smarter and more interesting. Eventually civilization.

In the Hitchhiker's Guide to the Galaxy, the mice were in charge of the world, working as lab attendants.

You can of course come up with your own aliens. Perhaps house cats run the world. Or blame the trees. James Schmitz wrote "The Pork Chop Tree" where psionic trees would alter every animal species to be dependent on it. In that case, it also got rid of pesky things like sentience. But perhaps your trees have a different goal.

How do you build a transistor radio on a deserted planet? You need a semiconductor industry. Now in that case obviously you'd sacrifice making a transistor radio in favor of making something without as many requirements, e.g. a vacuum tube radio. But what if you couldn't? What if you needed a whole solar system's worth of resources to build the basic capability?

Assuming you're effectively immortal (don't die of old age, only illness and injury; or can pass memories to descendants perfectly), you might plan to uplift species on each habitable planet. That way rather than having to wait for them to spread out and colonize, you can uplift multiple races simultaneously and grow their populations at the same time. Each race can specialize in different things so that when they combine, they'll be strictly more capable.

Your aliens may not have opposable thumbs. They may be accustomed to work with others who handle the more active tasks. Perhaps they simply don't reproduce often enough, or they happen to be missing a sex. So populating the planets themselves is not feasible.

It's a similar trope to the ancient founders' race, but not the same one. Which could allow you to make it fresher.


We were them.

We built this civilization. After that

  • some catastrophe happened
  • a civil war happened
  • our civilization went into a bad direction (example), and after thousands of years of slavery we degraded and fallen apart.

The ancient race is not so ancient. In fact it is still around

You ancient races actually around today they are hiding from an old enemy and trying to give the impression that they've been wiped out so they leave their ruined cities above ground while they secretly live in high-tech underground bases.


I think you could tie in a group of sentient beings that have managed to contact each other through magic or telepathy and are therefore already aware of the other planets and have their own agenda - They have alway known of the existence of the other worlds and have used that knowledge for their own purposes and have shared their development with each other to suit their own desire to connect with each other or achieve some mystical, magical goal.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .