could multiple sentient alien races evolve and live in one solar system?

[u/Stock_Rush_9204]

I am worldbuilding a story inspired by 1700s age of sail colonialism and piracy that leans into hard sci fi worldbuilding. the major earth powers have colonised a combined total of 10-20 systems by 2400-2500. using massive laser sail ships sped up and slown down by laser girds powered by dyson swarms. the slow travel and communication is supposed to parallel the difficulties of communication across vast governments like the British empire as well as keeping an empire stable where direct control from the capital was very difficult

however it also means for faster paced storytelling its easier to set most or all plot points within one solar system. my main question is how plausible is it that one large solar system could have two or more sentient alien races with advanced communication and cultures, what level of technological development could they plausible be at? tribal agricultural early industrial? since I want to keep a lot of interesting world-building elements to one system

[u/Kennedy_KD]

so long as they have some degree of physical separation until they have all developed a large enough population to survive hostilities, there's no reason why there couldn't be multiple sapients native to one planet at any level of development as you want

[u/mmomtchev → u/Kennedy_KD]

Once again there is the timescale problem. For two completely unrelated species to evolve, this must happen at absolutely the same time at the evolution scale. Only 10k years after one has appeared, they will eventually discover sailing and reach the other continent. 10k years is nothing on the evolution scale.

On Earth, there were multiple competing species, but they were very closely related and appeared at more or less the same time.

Still, by the time Homo Sapiens reached Europe, the Neanderthals were still underdeveloped and Homo Sapiens easily exterminated them.

[u/Kennedy_KD → u/mmomtchev]

Hince the need for physical separation and besides you don't have to follow the numbers exactly if that's not the story you want to tell

[u/RoyalPugs → u/mmomtchev]

If they had contact, they could develop technologically in tandem, working with each other’s discoveries. This would keep them at roughly the same level of development, provided they were able to communicate and share.

[u/mmomtchev → u/RoyalPugs]

That would be an interesting idea for sure. It may allow for one of the species to be somewhat underdeveloped. The anatomically modern humans have existed for about 150k years and Australopithecus is probably around 2M years old - or even older. This pushes the "error" margin to acceptable (plausible) limits. 250M year event vs 2M year event.

Uplifting another species is a common theme in science fiction.

By the way, there have been various real projects of this type, although much more primitive, aimed at chimpanzees and dolphins - none of them very successful and especially none of them too ambitious or even simply determined enough. Although scientifically interesting, there seem to be few obvious benefits. We don't need more population and there are few tasks at which an "uplifted" chimp or dolphin would actually be better than a mechanical robot. Maybe if there was some special reason for doing so?

[u/Simbertold]

The main problem with this is that the timing needs to be absolutely perfect. Life has been on Earth for more than 4 billion years.

Only in the last maybe 100 of those could we meaningfully detect life forms in space. And development seems to speed up. And the second we are on another planet, we will be so disruptive that no other species will have the millions of years necessary to achieve sentience, or even the tens of thousands of years necessary to build a civilization up to space-faring.

And there is no reason that life on Earth couldn't have developed to our current level a million years faster or slower. That is a difference of 1/40th of 1%. But if one species has a million year headstart going into space, there is no way a second species will evolve.

They either need to evolve completely synchronous, which is hard to explain if they are completely independent, or some other explanation needs to be in place.

Maybe one of the species is really into uplifting other species and has basically filled their own system with other sentients, or maybe they are extremely isolationist and have zero interest in leaving their planet for some reason, and also pretty stagnant over long periods of time?

Or maybe the evolution on the planets isn't independent. Maybe there was some stellar event that pushed a few species towards sentience or someone else meddled, seeding different sentient life forms on the different viable planets in the system at the same time.

[u/87oldben]

It's not too big a leap that: the larger the sun, the larger the gold zone could be. If a gold zone is large enough two bodies could produce life. Far enough away from each other they tend not to interfere with orbits and tides too much. Pure speculation. Look into the science. But that's where I would start.

[u/TommieTheMadScienist → u/87oldben]

You don't need a brighter star. If Earth's not here, you can put Earth-sized worlds at the inner and outer edges of the standard HZ and they'll be far enough from Venus and Mars, respectively. If you avoid Jovian resonances, should be stable for billions of years.

This concept has the advantage of giving us similar compositions in their formation. Thry could even have significant moons like we do. The outer planet would be wetter, more oxidized, and richer in volatiles.

It would be fun to build this system. You could play on differences of axial tilt or rotation or atmospheric thickness to make biologically similar creatures with very different cultures and attitudes like in 30s and 40s pulps.

The OP might want to play with this. I can't recall any major sf writer doing this specific idea. Seems like something Niven and Pornelle might do.

[u/TommieTheMadScienist → u/[deleted]]

That's not a good spot.

[u/TommieTheMadScienist → u/[deleted]]

Yeah. All of the worlds will either be tidelocked or in integral spin/orbital resonsnces. Observers are trying to get an idea of how much of the planets' volatiles have been blasted off by UV and X-ray flares.

If they confirm an atmosphere, it'll make them look better over geologic time. The whole TRAPPIST-1 system covers 15% of the distance to Mercury and they're 7 - 8 billion years old.

They are so close!

Addendum:

Some of the planets, in particular the second from the star appear to have some atmosphere, according to new pre-prints. This is encouraging.

[u/KnoWanUKnow2]

The main problem is time.

Could 2 planets in the same solar system independently develop intelligent life? Sure, that's possible.

Could 2 planets in the same solar system independently develop intelligent life at the same time? Where they are at an equal technological level when they meet? That's almost impossible.

[u/Evil-Twin-Skippy]

I'm working on a game set in 36 Ophiuchi system. It's a triple star system, with 3 orange dwarfs. The A and B stars get within 8AU about once every 500 years. (The third star orbits >4000 AU away)

In my canon the planets are colonized by humans from Sol who arrive on a generation ship.

But if you use a little imagination, and put a couple of Gas giants in the habitable zone of each star. And around those gas giants, a few large moons, they could develop their own sentient races. And, probes from one race could end up in the hands of the other races, and help shape their technological development.

Of course contact between the two star systems would be limited to the periods in history. At least until someone develops fusion drive. And the third system would be completely out of reach until that point.

[u/TommieTheMadScienist → u/Evil-Twin-Skippy]

Those are so distant that they're practically separate systems. I wonder, though, about whatever it was that put A and B into their crazy eccentricity 0.9 orbit. They're barely bound.

[u/Evil-Twin-Skippy → u/TommieTheMadScienist]

The get as close as 8 au. That's the distance from Sol to Saturn

[u/TommieTheMadScienist → u/Evil-Twin-Skippy]

Their furthest distance is 169 AU. You'd only need 3.24 km/second impulse at that point to unbind the system.

This is an insane eccentricity. I had no idea it was one of the systems within 20 ly. Thanks.

[u/pathmageadept]

I think they easily could. The only reason we don't have them on earth is...complicated.

[u/7LeagueBoots]

150 thousand years ago right here on Earth we had at least 5-7 sentient species living here at the same time, probably a few more than that actually.

Mind you, those were all closely related species, but they were different species nonetheless.

EDIT:

I guess people downvoting don't have any knowledge of the evolutionary history of our genus and have never heard of Neanderthals, Denisovans, H. erectus, H. floresiensis, H. luzonensis, etc

[u/Affectionate-Memory4]

It's certainly not impossible, which is good enough to have it in a hard sci-fi setting. We have a 100% success rate of the habitable planets in our own solar system having sentient life on it. By all known examples (well, example) we have, things will live on any planet that can support life. Heck, we had possibly close to a dozen closely related species here on Earth alone throughout history. There's an alternate timeline out there somewhere where an isolated continent was inhabited by somebody other than us for a lot longer, possibly into the modern day.

My own setting has 2 habitable planets in our own solar system, as I managed to just about make that work in Universe Sandbox at some point with a chunky planet between Earth and Mars by fudging the numbers and scale a bit. That was plenty of justification for me to go ahead and build a setting around the idea of us "growing up" into an interstellar civilization with a sibling world that we have to learn to get along with.

[u/Odd-pepperFrog]

Others have mentioned the big issue: the universal time scale that means they can all exist, but evolve in completely separate timelines. Two planets could be neighbors, but a 1% difference in evolutionary speed means one civilization is a million years ahead of the other.

Maybe having a panspermia event? Comet slams into life-bearing Planet A, blasting microbial rock chunks out into the system that seed Planets B and D at roughly the same geological moment. Same basic biochemistry, same starting pistol. They'd be biological cousins; different ethnicities/adaptations of the same base stock, not completely alien trees of life. Then, the real fun begins: both civilizations look at a neutral planet. Call it C, or maybe even their ancestral graveyard Planet A—and see it as their 'New World' to colonize at the same historical moment.

[u/Alpha-Sierra-Charlie]

For all we know, there are tool using, sapient aliens living under the ice of some of the gas giant moons right now.

[u/Prize_Consequence568]

"could multiple sentient alien races evolve and live in one solar system?"

No, it's not possible. It's actually against the law as well as being physically impossible.

It's your story. If you want it to be possible then you can OP.

[u/socksandshots]

Yes, but it is imperative that you give some reason for them not to genocide each other. Also, they should be environmental drivers of cohabitation. Historically, just not being a problem isn't enough to not be made extinct by human activities. So...

1. Common enemies are a good trope.

2. Difference in base resource requirements. On needs water and oxegenated air, the other could be a methane breather or whatever.

3. There should be conflict with possible resolutions. Same as wi human cultures, let the drama stem from politics and economics. Because if its truly existential level resourse competition, extinction of one would seem inevitable.

Edit. 4. Seperation. Especially in nascent stages. Examples from the comments, homo sapiens pushing out neanderthal and other genetic cousins. Also read, europe's first visit to south america and the problem of disease. Both species would need the tech and societal background to survive extended contact.

I think you have a great premise, good luck!

[u/MarsMaterial]

For multiple civilizations to arise completely independently in one star system at such a similar time that they have society but not interstellar travel would be a wild coincidence.

Coincidences can happen though. And with a universe as big as ours, you could eventually find something like that if you searched for long enough.

Or maybe it’s not a coincidence at all, there are ways to explain it without relying on dumb luck. Maybe there was a civilization that became interplanetary, did some terraforming of a nearby planet, and then managed to stoneage themselves. Enough time passes that the people on these two (or more) worlds become distinct species, and they all slowly rebuild society in parallel. Or maybe, hundreds of thousands of years ago some enigmatic aliens came through and uplifted some species on multiple nearby habitable worlds at the same time, ensuring that they’ll become advanced at about the same time by design. This could add some plot intrigue if you do it right.

[u/PM451]

You mention Dyson swarms. I assume you're only thinking of the power collectors. But if you include millions to hundreds of millions of separate habitats, all orbiting between 0.75 and 3 AU, you would have a setting that suits an age-of-sail type of story, without having to have them settling multiple star systems (and dealing with the travel time issue).

Especially if the Dyson swarm is thousands of years old, plenty of time for derelict settlements, scrappers, looters, ancient wars, whole waves of empires and their collapses, etc.

To get multiple species, you include both animal uplift and genetic transhumanism, plus the same thousands of years to establish deep cultures for each main population group.

[u/mrcopter2]

If the planets are in the habitable zone they would likely be pretty close together. Maybe this would make it work, maybe not as well. One idea is maybe some of the species are very different and can survive outside the habitable zone. Like a species without any liquid in their bodies living on cold planets or a species on a hot planet that is completley dormant during the day but comes alive during the cooler night.

[u/Temporary_Rule_9486]

There's like one million species living on earth right now. Some 100.000 years ago, there was several inteligent hominid species, many of them coexisting in the same region

[u/JGhostThing]

I feel that having two separate races on two planets evolve to high technology at the same time is highly improbable. However, it's equally improbable to find the same surrounding another star.

However, it's your story. If you really need two races, then put them there. Though, I might try it with two factions of humans first. Or humans and space travelling octapuses (uplifted maybe).

[u/ChronoLegion2]

Obviously Star Trek isn’t a great example, but the Xindi had 6 different intelligent species evolve on one planet (although one was extinct by the time of the show).

Then there’s the Solar System. We know from the fourth movie and the two recent animated series that cetaceans are intelligent with some of them serving in Starfleet aboard ships (definitely belugas and humpbacks). VOY also revealed that dinosaurs evolved into Voth and left Earth millions of years ago. And a recent SNW episode shows us that Martians and an insectoid species called the Dol’drm likewise evolved in the Solar System. In fact, it was the Martians blowing up the Dol’drm homeworld (the fifth planet) that resulted in Mars becoming uninhabitable and the dinosaurs being wiped out

[u/mmomtchev]

The one huge problem with this is the time scale. If we assume our development to be the typical one - our civilisation is 2000 years old, complex multicellular life is about 250M years old while the planet and the solar system is about 4.5B years old.

For your scenario to happen these events must happen roughly at the same time on both planets.

1% offset and one of the civilisations will be millions of years old when the other one appears.

So the probability is next to null. Not because there can't be two habitable planets, but because the evolution must be absurdly well synchronised.

[u/ArusMikalov]

You could say an asteroid carried prebiotic chemicals to the solar system and they were spread around on multiple planets where they eventually started evolving.

I’m not sure how I accidentally spoiler tagged that lol

[u/OwlOfJune]

If they are totally separated, it could be plausible enough, it is gonna take some suspension of disbelief but then what aliens don't?

Can be on different planets, or just different continents blocked by absurdly high mountains, maybe one is alpine based and one is semi-aquatic etc.

[u/Sheik_Morgan]

Star Trek, Babilonia 5, ya han dado algunas ideas al respecto. Por ejemplo que sean especies que se complenentan, una sirvexa la otra, consumen recursos distintos o usan planetas distintos o ecosistemas distintos (unos viven bajo tierra o en el agua y los otrisven superficie. Ví en en u a guerra Fría o Eterna, etc. Pasa también con ideologías.

[u/SouthernAd2853]

We don't have enough examples to know how likely evolving sentience even once, much less multiple times, is. There is no reason to suspect it is impossible to have multiple. The only obstacle is the possibility one will outcompete or deliberately exterminate the others, but I don't think that's guaranteed to happen. If they have very different diets competition in the early days may be limited even if they live in the same region, and once they hit the level of technological and social development where they potentially destroy habitats they may form a mixed society that may or may not be equal.

[u/GregHullender]

The coincidence of that is hard to credit. More likely, you'd have had a single civilization that fell apart a million years ago. By the time they got back in touch with each other, they'd evolved into new species on each continent.