From the little green men of Mars to the rubber foreheads of Star Trek, aliens persist as a tried-and-true staple of science fiction. Though the concept of alien life isn’t unrealistic, scifi representations are almost always implausible. We’ve recently deduced that Earth-like planets should number in the billions in our galaxy alone, so life – even intelligent life – should be common. But there’s no reason aliens would look, sound, or act remotely like us.
You don’t need to look beyond Earth for an example of why this makes sense: the two most intelligent animals besides apes are dolphins and the crow family. Minor tweaks to history could give Earth very different representatives on the galactic council: large aquatic creatures possessing an entirely alien sense (echolocation) or tiny flying scavengers descended from dinosaurs. A single planet with a relatively narrow range of environments* and just one biochemical “language” can give rise to incredible diversity.
What’s more, the differences between life forms on Earth can give us hints about how aliens might look and behave. Life has evolved to solve specific problems. Some of these problems – and the solutions evolution comes up with – are weird, random, or arbitrary. But other problems are universal physics quandaries: how to streamline for maximum swim speeds, how to create lift and stay flying, how to focus light in order to see.
To discover aliens from Earth-like worlds, we don’t have to travel trillions of miles to seek them out – let’s just go back in time.* We’re not going to give Hitler an art scholarship or prevent the fall of the Roman Empire; we’ll rewind time to when Earth was a lifeless rock and force biology to do a hard reset. When we re-run Earth’s “Make Life” program from an infinitesimally different random seed, what happens? What aspects of life are arbitrary, and what are set in stone?*
Luckily, we have a dimension ship at our disposal, so we can visit this alternate Earth and gaze in wonder at its Earthenoid inhabitants!* What unfathomable alien vistas await us?
What if there is no life here, only our deaths?
This journey to an alternate Earth assumes that complex life developed to begin with. It’s possible that when we step out of our dimension ship we suffocate in the atmosphere of nitrogen, carbon dioxide, and methane. Whoops. Guess we should have looked out the window and checked for obvious signs of photosynthesis before getting outside. Large complex life probably requires oxygen, (it’s a waaaay better fuel source than anything else on this planet) and an oxygen-rich atmosphere is only going to exist after the Earth evolves the right kind of photosynthetic bacteria or algae.
It’s even possible that no life exists on Earth at all. It’s difficult to gauge how unlikely life is going to be, just as it is difficult to gauge how likely it is for complex life to arise once single-celled life exists. All we know is that both things take a lot of time – time measured in billions of years. Resetting the Earth’s life might be like resetting the lottery after discovering that you have the winning ticket.
Even if complex life exists where we’re headed, and doesn’t immediately try to eat us or dissect us in a lab, we need to be concerned about carbon dioxide levels. Significantly lower or higher levels of CO2 could cause us to hyperventilate and possibly fall unconscious. Probably not lethal, but problematic enough to limit our tour to a few minutes.
Earthenoid Animals
Alter-Earth’s animals – let’s call them earthenoids – would be the first things to grab your attention* after you step out of your dimension ship. They skitter, they lope, they screech, they reek. They’re none of the right colors or proportions, and they’re too slow or too fast. All in all, they look, sound, move, and smell entirely alien.
That is, except for a few noticeable similarities:
Bilateral Symmetry
Their left sides will look like their right, though it may not be true symmetry. For instance, our heart is on our left side, and our liver is on our right. Simpler organisms resembling Earth’s sea stars and jellyfish may have radial symmetry.
Eyes and Mouths
Everything that wants to navigate the world and feed itself needs eye(s) and mouth(s). And since eyes and mouths have similar design constraints regardless of species, they’ll probably be recognizable even for beings that are otherwise totally alien.
Size
Size is limited by Earth’s gravity and atmosphere. These earthenoid beings might be a bit bigger or a bit smaller than us, but assuming they’ve had a while to evolve, they won’t be bafflingly enormous or microscopic. All bets are off for water-based creatures!* While it’s true that some of our Earth’s dinosaurs were pretty huge, during the “age of the dinosaurs” most creatures were roughly human-sized or smaller; the big stuff just stands out.
Shape
Unrelated species can share common traits because they have the same physics problems to solve.* This is why unrelated orcas, tuna, and earthenoid goobleyfish* all have sleek, torpedo-shaped bodies.* Similarly, all flying creatures will be as light as possible with large wingspans.
The “how to move over land” problem has many more solutions than the physics problems associated with flight or swimming. Just like on our Earth, ground-bound earthenoids walk, lope, run, scuttle, slither, ooze, hop, skitter, and… bound. Legs of some kind are common, but they’re not required, and they could come in any number.
Earthenoid Plants
The backdrop for these bizarre earthenoid animals isn’t quite so strange. The earthenoid plants are odd, to be sure, but the basic shapes of forests, savannas, and (especially) deserts are the same. Plants have simple jobs: soak up sunlight, grow, reproduce, don’t get eaten (much). While plants on the Earth we came from had all sorts of ways to do these jobs, there’s one generic catch-all strategy that remains the same: grow really, really tall. So while the undergrowth might appear a bit confusing and alien, earthenoid forests will be recognizably forest-like, if oddly colored.*
Like animals, plants have size limits imposed by gravity and atmosphere. Competition would ensure that tree-like plants grew high enough to actively push against these limits – just like trees do on Earth.*
Under the Microscope
Earthenoid life would still be made of cells organized into tissues organized into organs organized into organisms. True, there are some animals from our Earth that exist as giant undifferentiated blobs (looking at you, sponges and coral). But amorphous simplicity doesn’t work well on land, especially not after a billion years of evolution herding life toward more compartmentalization and specialization of tissues.
It’s fair to expect earthenoid organs to look freakishly weird, but some basics will still be in place for complex life larger than an Earth worm: heart(s), lung(s)/gills, brain, digestive tract, muscles, and frame (bone or exoskeleton). That’s because blood-like fluid needs to get pumped, oxygen needs to get harvested from the air or water, motions and behaviors need to be coordinated, and food needs to be digested. Also possible are stingers, poison sacs, gas bladders, livers, gall-bladders, spleens, and all sorts of other “optional organs” that we see on our own Earth.*
Like the physics problems experienced by flying or swimming life, cells experience identical chemistry problems, forcing them toward the same solutions. Thus the similarities between earthenoid life and the life from our Earth increase as we zoom in to look at cells and molecules. At the most basic level, earthenoid life is still carbon-based, still using water as a solvent, and still (for the larger, hungrier life) using oxygen metabolism. There are alternatives to carbon molecules, water solvent, and oxygen metabolism out there, but these are by far the best options for life on any Earth-like planet; they won’t be changing when we do our reset.*
We find Earthenoid life organized into cells. In order for complex life to survive, these cells must have some basic functions carried out by specific sets of building blocks:
- Libraries of data (built with DNA & closely related RNA)
- Molecular machinery and scaffolding (mostly proteins, but also some RNA)
- Walls, shells, and compartments (lipids, also known as fats)
- Fuels stores (often sugar or starch, but could be any organic molecule)
While these functions won’t be provided by the exact molecules listed, only a handful of those molecules’ close relatives would be up to the task under Earth-like conditions. We’ll find that earthenoids use a slightly different chemical language or have slightly different “building codes.” Maybe a chemical relative like PNA replaces our DNA, or the proteins use a different “alphabet.”* Their libraries might all be backwards or written right to left instead of left to right. Directionality is just as arbitrary in biochemical languages as it is in written languages. But this alphabet would be, to us English readers, more like Cyrillic than Chinese: many of the letters will be recognizable.
We could take a gamble and eat some earthenoids if we got really hungry, because they’ll probably use the same energy-rich building blocks as life from our Earth. But even if they do, there’s a fifty-fifty chance that all their molecules are mirror-image (chiral) versions of ours. That’s not a matter-on-antimatter mega-explosion scenario; rather, it would just make us sick and not fulfill any of our protein requirements.* This is probably for the best, since it also means that bacteria and viruses that we’ve inadvertently brought with us probably won’t be able to thrive here when they don’t find the right sort of food.
Intelligent Eartheniods
Weird alter-Earths filled with strange plants and animals can make great scenery, but we won’t get as much mileage out of an alien world without, well, aliens. Though there’s no guarantee we’d find life of human-or-better intelligence here, it’s not unlikely. What is unlikely is that it would look anything like us; intelligence can arise anywhere.
We can expect intelligent eartheniods to be social creatures. Evolution is actually less about competition between species and more about competition between individuals of the same species. And when a species has an intricate social structure, greater intelligence increases an individual’s ability to navigate it – just like saying and doing all the right things on a date will help a human get laid.
Increasing intelligence allows for more complex social structures, which demand increased levels of intelligence. This upward spiral to sapience can happen for any species, though it helps if the animal had some smarts to begin with.* The process is limited by how cumbersome, energy-consuming, and vulnerable the brain becomes. Evolution works around these limits by making increasingly efficient brains.
This process is less likely when members of a social group share genetic material. For example, ants and bees are highly social, and their societies are complex, yet they face little pressure to gain intelligence. They aren’t in competition with their siblings; their genes do just fine if they always put their group’s welfare above their own. So earthenoid hive minds are unlikely, though if humans are any indication, earthenoid cultures could still create groupthink.
And don’t forget, there could be multiple intelligent species sharing the world – so long as they occupy very different niches. Humans are land-based species able to exploit almost any niche. We also actively killed off all our sapient rivals because we’re jerks.* But imagine if crows and dolphins simultaneously beat us to the intelligence threshold. They’d be much more amenable to sharing the planet, since neither would bother with the others’ territory.
There’s not much else we need to see here – unless the intelligent earthenoids are so far beyond humans* that they’ve explored space and contacted true aliens. But even that would be superfluous; we’ve already seen the truly alien. Hopefully the experience has been strange enough that we vow to keep humanoid “rubber forehead aliens” out of our science-fiction stories from now on. The realistic options are less relatable but infinitely more varied and interesting.
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Although N.K. Jemisin has significantly diminished my desire to read about alien species, this is a very thought-provoking topic. I hope Mythcreants will make more science related content.
Who’s N.K Jemisin?
Octopuses are pretty smart too, and apart from humans the only preemptive tool users. By which I mean that apes and crows both make tools, but only when the need for them becomes apparent – whereas octopuses that use coconut shells for armour or rip the tentacles off of jellyfish to wield as deadly whips do so before getting into situations where they need armour or deadly whips.
You’re absolutely right there. Plus octopuses (octopi? no idea) can live on land for a certain amount of time and can be found crawling around by using their tentacles. If any species is ever to take over earth from us, it’s probably going to be them.
I, for one, happily welcome our new, eight-tentacled overlords!
But I hope someone manages to delete all Hentai porn before.
>using our imagination, which is a significantly less stylish method
Speak for yourself. I’ll have you know that my imagination is quite stylish!
Interesting article! Just comments about some of your specific points:
Photosynthesis: I have heard some arguments that chlorophyll is mostly used on Earth because it is the most efficient molecule for photosynthesis (after all, the Sun does not primarily emit green light, so there has to be a significant advantage for chlorophyll and maybe star color doesn’t even matter). On the other hand, it could simply be that evolution doesn’t always find the absolute best solution and chlorophyll isn’t superior. There is also the possibility I just found that plants only absorb a narrow band of light to prevent overheating. This might mean that alien plants may not be black, but may not necessarily be green either.
DNA and RNA: There is some evidence that our genetic code is not arbitrary. Specific nucleotide orders code for specific amino acids, and some studies show our specific arrangement may have a function such as minimizing the possibility of errors, or it might be determined through chemical affinity. If true, this might mean that Earthlike aliens will share the same kind of genetic code. Might.
There also have been claims that DNA and RNA are the best possible genetic material. Certainly nucleic acid analogues have been constructed in the lab, but it’s unclear whether they are easy to form naturally or are as good or better as DNA. Of course, there’s no proof that they wouldn’t work either.
Chirality: Some processes might mean our left-handed chirality is non-random. However, most scientists believe other carbon-based life forms may use different chiralities after all, and while space radiation can preferentially destroy one form, that seems to depend on which way it is polarized and may differ across solar systems.
Intelligence: For your discussion of ants and bees, they’re often considered pretty intelligent (for insects, at least. I’m not even getting into how difficult comparing intelligence among species can be; for instance, bees can outperform computers at the traveling salesman problem.) There can actually be conflict within eusocial species; for instance, queen-worker conflict due to differing genetic relatedness. See worker policing, in which workers try to prevent other workers from reproducing. I also heard of a wasp with a strict dominance hierarchy and an evolved ability to recognize individuals.
There is also another thing to consider: even if something is intelligent, can it physically create technology? This might be a concern for something aquatic or without hands, such as the dolphins and ravens you mentioned. However, there have been a few proposals for how technology could develop underwater, and there’s a lot of debate to what kinds of appendages could function similarly enough to hands to allow for the building of technology. (I wonder how it could be tested – robots or simulations, perhaps?)
Ants and bees are much smarter than you give them credit for. They have a notable level of language, tool use, teaching, and basically everything humans needed to form our civilization
They also have slavery, so they can’t be that civilized.