Could Two Alien Races Evolve on the Same World?
This episode is sponsored by Raycon. We often wonder if in all the billions of planets in this galaxy, another intelligent species might have arisen on another world, but what about the possibility of two arising on the same one? A few months back in our Valentine’s Day episode on Multi-Species Habitats, we examined the classic science fiction trope of marrying aliens and having hybrid children with them. It’s also fairly common in fantasy genres too, usually half-human, half-elven children and such. However, a less common trope in science fiction is two separate species coming about on the same planet of origin and not interbreeding at all.
This is much more common in fantasy though, and certainly in human mythologies, for presumably two reasons. First the action on fantasy tends to be limited to a single world, so your nominal aliens have to be from there too, and second and probably more importantly, these are usually predicated on one or more deities having directly created the intelligent species in question, so we need not be concerned about the seeming improbability of two separate species both getting intelligence at roughly the same time. This is not like us and the Neanderthals, who are simply another branch of intelligent hominids we share a common ancestry with, and indeed with whom we have increasing evidence of interbreeding, but rather something very far apart. It is not hard to imagine some fantasy equivalent like elves or dwarves as fairly close relatives who may be only many thousands of years apart from us genetically, but if we’re talking lizard people or walking and talking cats and dogs you’re looking at millions of years of genetic divergence. It seems improbable that two divergent lines separated by millions of years would hit intelligence at roughly the same time so that one would not dominate or wipe out the other before they got smart too. We’ll be looking at both how improbable that really is and the various ways it might happen anyway.
We should note that in many ways, this is the same question we often deal with regarding the Fermi Paradox and our galaxy. Humanity has been around and using fire for about a million years, and sending objects and people into space for less than a hundred. I would be quite surprised if a million years from now there was a single star in this galaxy that our genetic or technological descendants had not yet reached.
So if we assume two million years is about the average time it takes a newly sapient species to get civilized and colonize the galaxy, but this happens rarely enough that others haven’t already conquered our galaxy, then it’s highly improbable that two rare species’ two-million-year epochs would overlap much. So two spacefaring species meeting and finding out they’re anywhere near the same levels of technological development is as highly improbable as two species evolving on a single planet and having roughly the same level of intelligence. But it’s not ridiculous, and there are scenarios in which it’s plausible. Consider that we’re not talking about two entirely alien paths of life arising on a world, just two distant cousins.
Ones sharing the same basic biology, rather than say a world on which carbon-based and silicon-based life both arose, though that might be an interesting discussion for another time. I’m not sure what the nearest common ancestor of dolphins and octopuses is, but it would be an invertebrate much older and not nearly as intelligent as either of those critters. And yet these two very distant cousin species are in the same general zone of intelligence. We also have many other smart critters of distant relation, cats, dogs, elephants, racoons, and more. Now there are more levels of intelligence below human and above average mammals.
The second smartest critters on the planet after humans are our close relatives chimpanzees and orangutans, both of which are demonstrably smarter than all those other cute critters I just mentioned. They’re also dumber than other effectively extinct near-human lines, of which Neanderthal is but one. We don’t know how long these various smart critters have been as smart as they are anymore than we know what drove humans to high intelligence, but we can speculate on various causes and we can also recognize that what caused it here doesn’t have to be the same as what caused it elsewhere. As an example, one of the strongest candidate theories for why intelligence evolves higher and higher is as part of a predator-prey cycle. This is where an improvement in one of them, like the prey getting faster or smarter, pushes the predator to get better or smarter if it wants dinner, and vice-versa, an improvement in the predator can drive improvements in the prey to avoid becoming dinner.
The hare gets better at finding places to hide and the fox gets better at finding them. It need not be as simple as foxes and hares, you could have two smart critters who don’t eat each other, just compete with each other, who get smarter for that competition for resources. We can also imagine some predator akin to a spider in methodology, that is relatively dumb or weak itself but spins traps and prisons for its prey and hunts pig, racoon, and monkey alike. They get captured in the web-equivalent, but can think up a way out to escape it, and pigs are quite clever at escaping pens, or racoons for getting into containers.
All three smarter creatures are prey to this dumber critter which has recently and successfully evolved superior trapping skills, forcing all three to adapt by getting smarter or to perish. We can use spiders not just as an example of creatures that trap their prey, but because spiders have a rather novel way of flying, by spinning a silk strand and floating away like some upside down kite, that lets them travel kilometers high and cover over a thousand kilometers of distance. So they can migrate continents, whereas a pig, racoon, or monkey, smart though they are compared to a spider, have a harder time crossing continents if the land bridge between them goes away. So we could imagine three isolated continents, isolated to the prey at least, getting simultaneously preyed on by the same predator. These bigger smarter critters also relatively few in number, so in the case of lone member of that species making it across the sea somehow, for it to successfully thrive, it needs to be able to survive in a new environment, find a cousin it can breed with, successfully do so, and have that offspring be fertile and survive.
This is quite an uphill battle, and a land bridge offers the option of a cohesive pack or herd of the organism making a crossing, offering much better odds. But we know all about land bridges here on Earth, and they probably aren’t that rare in galactic planetary layouts, and let’s start with this simplest case: divergence of an already smart species by land separation. We wouldn’t expect them to be that much different, two or more clades of a species separated by something like what we had with the Americas from Africa, Europe, and Asia, but given that folks often think of elves or dwarves or such as different species, it's plausible enough. We also don’t want to assume evolution is the same in details and timelines everywhere. The basic premise yes, but we can’t assume a given planet is going to have its human-equivalents having lifetimes, generations, and population densities anything like ours. It’s a decent bet life anything like ours will need similar amounts of space and energy but there are some big ‘ifs’ in there.
For instance, even though evolution will tend to push toward optimal machinery, the neuron nature develops on one world with one set of chemistry might do the same job for half the mass and twice as quickly, or even an order of magnitude better… or worse. See our episode Non-Carbon Based Life for some more discussion of alternative chemistries. We should also keep in mind that cannibalism is common in nature, and at some point you have a divergence in a species of one chunk of it eating the other chunk, becoming predator and prey, and that can happen many times and intelligence is no bar on this, nor really is genetic similarity. Indeed we cannot take for granted that the problems we have with diseases passing through cannibalism would be a universal issue, even if pathogens were common, a different type of digestion might remove the issue. So we can imagine divergence of near humans akin to elves or dwarves, but we can also imagine the vampire equivalent, a sub-species that evolves to a predator-prey relationship. These near-human cases where the genetic separation is relatively recent isn’t our main interest today but they merit some consideration.
And again, while we might assume it would take a million years to diverge that much, that’s not necessarily true even on Earth, let alone alien worlds and species. For humanity we don’t seem to have diverged too significantly but even big barriers like crossing between hemispheres after the ice age don’t seem to have completely stopped the occasional exchanges of DNA, ideas, and goods so that we can’t really make a strong case for divergence on Earth. We might hypothesize that instead of humans reaching the Americas 10-30,000 years ago some early humanoids got there half a millions years earlier, and then the ice ages ended, that those two branches of humanity remaining might have diverged beyond the point of interbreeding. We might get something as visually distinct from humans as the mythological Yeti, while at the same time it would not be terribly implausible that they both continued to get smarter and kept parallel enough that once reunited by ocean-travel capable technologies the one who developed it had no special advantage in understanding or utilizing it than their cousins, once they’d been introduced to it. Same as with us only with more genetic differences that made interbreeding harder or less desirable.
Emphasis on desirable because you could have genetic divergence while separated by nothing more hard to cross than a creek, as opposed to an ocean. Bigotry is hardly admirable but also hardly rare, and probably not rare on other worlds either. So too, using that vampire example of earlier, for all that vampires often appear as romantic partners in fiction, a divergence caused by one chunk of a species turning cannibal on the other and initiating a predator-prey cycle is not likely to result in a lot of marriages and happy neighbor relations. For a given value of the words cannibal and predator of course. There are options for symbiotic relationships there, and we’ve often had groups, classes, or castes who had fairly predatory attitudes toward their fellow humans.
Humanity has frequently had class or caste based systems which were hereditary, and just because we tended to interbreed a lot even in those cultures which most staunchly opposed such mixing, doesn’t mean aliens would. A given alien race might view mate selection as more akin to investment advice than a deep spiritual bond, and adultery or accidental pregnancies might be essentially unknown. In a situation like that, where hereditary castes or classes existed and the culture could actually make it stick with few to no incidents of interbreeding for several hundred generations, you might end up with a civilization composed of various species who could no longer interbreed anyway. I also don’t find it too hard to imagine a civilization that could make hereditary castes stick that long and well might have some other issues with technological stagnation and innovation so that their march from early civilization to the stars might take a lot longer. Though that’s got a fair amount of human bias on it too, again a species that genuinely didn’t put much emotion into mate selection or career exploration isn’t necessarily one that doesn’t put emotion into parenting, friendships, or following any other rigid societal structure besides a day job.
Though we probably want to remember that a hypothetical species that was pretty logical and emotionless, like the Vulcans of Star Trek, is not the easiest thing to evolve either. Mate attachment has some valuable properties in evolution, especially in lifeforms needing many years to develop, as an extra parent doubles access to food, protection, caretaking, and teaching. Nonetheless we can’t assume any given type of emotional bond would be universal in presence or strength.
The genetic caste concept is a fairly common trope in fiction too, the alien race composed of very distinct and specialized sub-races genetically suited to their role, and one of the more interesting examples of it is the Moties from the Classic scifi novel “The Mote in God’s Eye”, which are hyper-specialized into castes, and maybe more justified in their case because they have cyclic apocalypses that keep driving them back to the stone age. Which is one way something like that could theoretically happen on Earth I suppose, the end of the ice ages ended the land bridges, and the reverse, a melting of the ice caps and hard core apocalypse that knocked us down to a handful of isolated surviving bands, say a few dozen tribes of a couple hundred folks each scattered across the planet, is exactly the sort of genetic bottlenecking that could result in a bunch of massively divergent clades of humanity. There’s a lot of scenarios that could result in one species splitting into two close-cousin species but this is not really what we mean by alien. It’s just your elves and dwarves equivalent, not your dragons or lizardfolk or other fantasy examples, which again usually assume a mythological progenitor being involved. Which is a scifi option too of course, ancient aliens transport critters to a planet, from various alien worlds or laboratory creations, and they simply can’t interbreed with each other anymore than trees and robots could with us or each other.
One could imagine some rather unlikable overlord race having a lot of such species around that they’d made incapable of using their technology, then dying off or leaving, and a million years later those critters evolved themselves back up to intelligence or reinvented tech. That does raise another option though for two very distinct races to evolve, we often talk about uplifting animals to be human-smart, which is obviously one way to get two or more intelligent races on a planet, but we also discuss how we might use such technology to assist a marine species we encountered on another world. We’ve often discussed how hard it would be to get technology on an ocean world for something like dolphins or whales, even if they were as smart as us, and if we might give them technology and assistance if we found them on another world. But it doesn’t have to be another world.
We might imagine Earth, if dolphins got a bit smarter before humanity evolved, where they were around a million years older with roughly our intelligence but never developed technology. Such a world might have entirely cordial and cooperative relationships between early humans and those dolphins, and then when humanity got around to developing fire based technologies and growing civilizations, the dolphins just came along for the ride. We are often contemplating two races on a planet being in fierce competition till one wiped out the other, and that’s certainly an option, but the land-dwellers and marine civilization don’t really have many natural points of conflict, have some good basis for cooperation and trade, and until you get to relatively modern technology, no realistic way to occupy each others territory or pursue genocide. For that matter, while we tended to assume we wiped out most of the other human cousin species in the Homo Genus, like Neanderthals, we have better reason to think we just interbred, and I’m not aware of any documented efforts in history to wipe out apes, chimpanzees, etc.
Given many of the nastier moments of human history, such genocides aren’t hard to imagine either, but should not be taken as a given with us let alone myriad aliens. This land-sea scenario strikes me as reasonably plausible, where the first species to hit high intelligence just wasn’t well situated to achieve technology, and was followed sometime later by one that could, and again it did take us around a million years to go from harnessing fire to using it for even simple applications like making pottery. Some marine based civilization might need far longer to get there if they could at all, but then seeing us using fire on the seashore, might easily understand it and suggest applications for it. Another scenario is that an event kicks off a technological race between various intelligent but non-technological species. Same as a severe asteroid impact might cause an earlier intelligent species to be broken into a handful of surviving and isolated bands that genetically bottlenecked.
Or instead of a single big strike, we could have something like a collision of iron-rich asteroids leave debris in a system that manifested on the planet as a bunch of meteorite strikes. So that you had lots of meteoric magnetized iron available that the curious natives played with or some natural event that made fires a lot more common and encouraged the various smarter species to figure it out and figure out how to manipulate it. We also have some potentially weirder scenarios. Consider some sort of fungal parasite that infested animals as a way of controlling them, sounds like pure sci fi but it's actually something not entirely unknown on Earth. We have a zombie fungus that infests an ant’s brains to force it to migrate to a place ideal for the fungus which then locks the ant in place there and sprouts from its head.
There are several other types of brain controlling parasites on Earth and we explored that concept a bit more in our episode Parasitic Aliens. However we might imagine a very sophisticated evolution of that into something like a neural network of fungi and eventually some sort of symbiotic rather than parasitic relationship. Now such a situation might result in a divergence of the fungi, with certain types specializing in brain control of birds while others got mammals or fish, or which specialized to the point of being able to do only one Family, or Genus, or even Species. Such being the case, thinking of this as an intelligent species of fungus may not be accurate at this point.
Indeed the fungus might just be a neuron equivalent to the host organisms of what mitochondria are to our cellular energy production. We don’t talk of various animal species being various subspecies of mitochondria, even though they are an entirely separate organism that’s formed a very long-term and specialized symbiotic relationship with all of us. Telling a hundred different intelligent animal species that they’re really one species of parasite or symbiote isn’t likely to make them feel all unified anymore than a cat and mouse might feel if informed that they share the same basic mitochondria.
Indeed, it’s not like Darwin’s “On the Origin of Species” suddenly made us feel a great kinship to cows, pigs, or chickens. Nor did it change our general attitude of good will toward cats, dogs, and horses, which predates thinking of them as relatives, so we probably should not assume two intelligent species could only get along in the primitive era in cases like our people and dolphins examples from earlier, where there was no particular zone for competition. Needless to say it isn’t hard to imagine them trying to wipe each other out either, we just shouldn’t take that as the default approach, let alone the norm with few to no exceptions. Perception is as important as reality when it comes to behavior, and humans have often attributed human level intelligence to various animals and rarely tried to wipe them out. Human caused extinction of other species has generally been a product of ignorance or indifference, not intent, and since we often have attributed much higher intelligence to various animals than they apparently have, we shouldn’t take for granted that if they actually had it, we would have sought to wipe them out.
Though of course it can certainly happen and presumably did for a lot of dangerous predators, lions and wolves for instance have both been species humans have tried very hard to eliminate in their environments. We also don’t really know how the various intelligence to survival feedbacks worked in human evolution, you could potentially have critters who were quite smart but not well suited for tool use run a parallel case to the dolphin example. Your human analogue species invents the technology and some other smart critters find it easy enough to use once exposed to it. Some might be smart enough to use it with training but not really understand it, following into some role with the other species paralleling draft animals like oxen or horses, while in another setup we might imagine them as smart but not adapted for a technology, and thus exchanging their own skills for use of it, like a tiger dragging in antelope to the clever monkeys in exchange for them using their nimble fingers for crafting this or that useful thing.
All in all, I still would expect the likelihood of two intelligent species evolving on the same world independently to be fairly small, but as we saw today, it’s maybe not quite so improbable as we might assume, especially given that their evolution to intelligence might not always be very independent of each other. Speaking of long term symbiotic relationships, one we tend not to have in the average modern household is goats or sheep for mowing the lawn, and I’ve generally found lawn and garden care a great combination of exercise and quiet time for thought or to listen to a good audiobook. However, mowers and a lot of other gear are quite loud, so it’s nice to have a good pair of earbuds with noise isolating features, without dangling wires, and at half the price of other premium earbuds, I’d recommend trying out Raycon’s Everyday E25 Earbuds. They’ve also got a good battery life and a very compact charging case with its own battery that can recharge them four times while you’re on the go, which means they’re recharging every time I put them back in their case for safe keeping, even when I’m far away from any power outlets. Raycon earbuds give you 6 hours of playtime, seamless Bluetooth pairing, more bass, and a more compact design for a comfortable, noise-isolating fit! Raycon is disrupting the electronics industry by designing premium wireless audio for half the price, without compromise.
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