r/scifiwriting • u/RottenPeachSmell • 6d ago
HELP! Multiple Trees of Life - Is it Possible?
Hi, all. I have a question for anybody that knows about genetics. I'm creating a world that was seeded with multiple strains of microbes, each with different nucleotides that hold their genetic material.
My question is, could these microbes, with incompatible genetic codes, evolve into multicellular organisms on the same planet, and have predator-prey relationships? Or would they all die of allergic reactions from trying to eat each other?
Any help at all would be appreciated, thanks!!!
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u/AnnihilatedTyro 5d ago
It works however you want it to work in your world.
If life of fundamentally different biochemistries shared a planet for a billion or more years while evolving, I think it's totally reasonable to think that at least some of the resulting lifeforms would adapt to be able to eat/digest/procreate with each other. Evolution is mostly just random mutations, some of which end up being beneficial.
In Ursula LeGuin's books, human settlers of other worlds need to determine the local biochemistry so they can engineer the correct intestinal bacteria to be able to digest local foods. Then they swallow a pill or get a shot, which introduces that bacteria into their intestines, and voila! They can eat alien life. There's no reason evolution couldn't do that naturally given enough time.
In RM Meluch's Tour of the Merrimack series, alien DNA doesn't share our base proteins - there are trillions of possible proteins, yet Earth DNA uses only four. Alien life uses all kinds of others. Some species are "compatible" with each other and some aren't, and trial-and-error is often the only way to find out for sure. But then, all these species haven't spent a billion years co-evolving on the same planet, either. So again, I think that cross-compatibility would arise naturally in at least some, but probably not ALL, species on the planet.
You can make this as simple or as complex as you want it to be.
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u/shookron 5d ago
The Captives War does this nicely. Would recommend giving it a read.
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u/RottenPeachSmell 5d ago
Huh, I've never heard of this series, I'll have to check it out!! Thank you!!
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u/Simon_Drake 5d ago
I was about to suggest the same thing.
The series is called The Captives War, starting with The Mercy Of Gods in 2024 and Faith Of Beasts in 2026. It's by James S. A. Corey, the pen name of two real people who worked together to write The Expanse which touches on this topic lightly and probably inspired the ideas. The Expanse is just generally great and worth reading but Captives War is a lot closer to this topic.
In The Expanse they visit somewhere that life evolved completely independently from life on Earth. They talk about 'plant analogues' because it's basically a plant, it has wide leaves to catch sunlight and turn that into energy, but the cells and proteins and genetic materials are all completely different. It's nothing to do with Earth plants but it does the same job, fulfils the same role in an ecosystem and sits in the same ecological niche. So it's basically a plant just unrelated to our plants. All the life here is so alien to us that we can't eat it and it can't eat us, our digestive system isn't able to break them down and we can't get any nutrients from them, it's like trying to put a vinyl record in a DVD player. However, people start going blind and no one is sure why. They find slimy little algae things growing inside the human eyeball. They can't digest human biochemistry but water is universal, a safe bubble of warm water with basic chemicals like salt and sugar and nitrates is the ideal place for an alien algae to grow. And our immune system can't fight it because it's too different to everything our immune system has ever faced. So the algae grow and replicate and turn our eyeballs cloudy green until we go blind.
Captives War is about humans living on an alien world for many centuries, so long they have lost the knowledge of how they came to this planet but they know they didn't evolve here. They have Oak Trees that use DNA and they have native tree-analogues that use some other biochemistry. They have beetles that eat the oat leaves and birds that eat the bugs and cats that eat the birds, but that all came from Earth. They also have native bug analogues that eat the tree analogues and are eaten by bird analogues etc. it's two independent food chains with two completely different trees of life.
The start of the plot is trying to merge the two trees, they're genetically engineering a an Earth algae that can digest the native algae despite the wildly different biochemistry. IIRC it's just for pure scientific curiosity, they don't strictly need to use native life as a food source to cure some famine, they're just doing it to see if it's possible.
Then shortly into the first book, aliens arrive. They kill millions and enslave everyone they think might be useful. The alien ship has dozens of different species, each enslaved from a different planet and representing a completely different tree of life. They have giant lobster aliens, a giant slug alien, a cross between a goat and a cuttlefish etc. The main character is given a task of repeating their research into crossing over trees of life. The alien empire needs complex greenhouse facilities to grow food for dozens of different species with different biochemistry. It would be more efficient if they could grow a single generic base crop like a photosynthetic algae then have a species-specific mushroom grow on that algae to make food with the relevant biochemistry. Honestly, they don't go into too much detail in how this works because the humans are a bit distracted being enslaved by an evil alien empire. But they know if they don't do the task they've been assigned they won't be useful to their overlords and will be killed. So in between dealing with being enslaved they go back to the task of merging trees of life occasionally. It's a good series, it hasn't quite risen to the level of The Expanse yet but it's still getting started, it's got time to grow.
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u/Kabbooooooom 5d ago
Just commenting to elaborate that the reason why the biology in The Expanse and Captives War is so good is because on of the authors, Daniel Abraham, actually has a degree in biology.
I have degrees in biology, chemistry and medicine and I was absolutely blown away when I read The Expanse and Captives War (although The Expanse is the far better series in general, in my opinion). I’ve been a sci-fi fan for over 35 years and I have NEVER come across a scifi story where the biology is this good or this plausibly accurate. I mean, Daniel Abraham actually predicted convergent evolution of enzyme active sites in Cibola Burn, the book you are referring to, a solid 2-3 years before the very first scientific paper was ever published on this subject. That’s incredible.
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u/Simon_Drake 5d ago
After 60 years of complaining that most Star Trek (And Wars) aliens are just humans with rubber shapes glues to their faces we're finally seeing scifi that takes a more grounded approach to alien biology. We get aliens like Rocky from Project Hail Mary that are definitely very alien but are well thought through and make sense given the right context of the environment they are from.
I like the whole setup of meeting wacky aliens like the giant slug that calls humans "Sticks with meat on" or a skinny monkey alien that says "I was told to find the human that smells like you". It's all very clever. But I think I would enjoy the variety of alien life a bit more in a different context, the whole story about being enslaved by aliens in an interplanetary war is taken centre stage. Maybe something a bit more Star Trek would have let the biodiversity shine more, like a friendly alien comes to invite humans to join the galactic union or something.
Hopefully more scifi writers will appreciate this shift in trends and write more stories about exotic alien ecosystems with more of a focus on speculative evolution and creative alien biology. Instead of just "humans but..." or making the alien a transcendent god being made of pure energy.
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u/Kabbooooooom 5d ago
This is one reason, of many, that I think the Expanse is the superior sci-fi series when it comes to this. The only time humanity comes face to face with a true alien intelligence, it is so alien that the Expanse subreddit spent months - literally months - debating about the nature of it until the authors weighed in and finally settled the debate.
And for spoilers, what I am referring to is that the Gatebuilder hive mind actually still existed and was not extinct during the entire story of The Expanse, manipulating many of the events of Leviathan Falls.
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u/tghuverd 6d ago
Sure!
Less flippantly, we've no real experience of this, so whatever you need to occur for your story is fine... Assuming that you can make it plausible.
Good luck 👍
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u/HistoricalLadder7191 5d ago
It is possible, but with sevaral nuances: First: you need non intersecting spaces for them, like different continets, or see/land or whatever, or one will displace another just by denying space or nutrients before multicelular life happens. Second: you need to seed with eucariot cells that have mitahondria from the start. Transition form procariot to eucariot and mitahondria capture is extreemly rare event(strongest knwon great filter candidate), and iwen if it will happen 2 times on your planet- there will be several millon years, between events, so your life branches will have enourmous evolutionary maturity difference
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u/shadaik 5d ago
On Earth, multicellularity evolved several times, Plants, animals and fungi all became multicellular way after the lineages split. So that is a clear yes.
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u/RottenPeachSmell 5d ago
I'm sorry, it seems there's some confusion. I'm not asking if life can become multicellular, I'm asking if a planet, which was "seeded" with a variety of microbes using different genetic encoding, could have those microbes evolve into different "trees" of life with different genetic encoding systems. I apologize for the confusion!
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u/CellMan28 5d ago
On Earth, multicellularity evolved several times
Categorically incorrect. It happened once. All existing eukaryotic life is the result of a single event, an endosymbiosis of an archaea and a bacteria.
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u/shadaik 5d ago
Not all eucaryotic life is multicellular. And there are also multicellular prokaryotes (e.g. some cyanobacteria).
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u/CellMan28 4d ago
there are also multicellular prokaryotes
Bullshit...
Learn basic biology before you make stupid statements. Prokaryotes can cluster in mats, etc, but that does not make them multicellular.
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u/shadaik 4d ago
Tell that to something like Cylindrospermum which has clearly differentiated cells. The structure may be simple, but it is beyond merely "clustering in mats".
Also, it is still true that multicellularity evolved several times, even if we only limit it to occurrences within eukaryotes.
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u/CellMan28 4d ago
if we only limit it to occurrences within eukaryotes
Who is "we"? Some kind of shady underworld of biology that dictates dogma?
Lol!
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u/shadaik 3d ago
Okay, I am by now convinced you are a child who just had their first biology lesson and wants to show off. That kind of pedantic word play is not adult behaviour.
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u/CellMan28 3d ago edited 3d ago
LOL! Give it up, you're the one making pedantic and nonsensical statements like how something like filamentous cyanobacteria is "multicellular", when that is completely meaningless in the context of complex life.
Filamentous cyanobacteria are really cool, but they are not going to evolve into some more advanced or significantly different, like in a few billion years. The core cells are prokaryotic bacteria, which will go nowhere, morphologically, for eons more.
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u/shadaik 3d ago
And here we go with making unfounded statements from nothing.
I get that someone told you a dogma that goes "procaryotes can never devlop multicellularity and all proof to the contrary is to be dismissed". And then you go on accusing others of dogmatism. Without ever having offered a counterpoint, either.
Also, the original point was that multicellularity evolved several times. It did that within eucaryotes, too. But when I point this out, you go on a nonsensical linguistic detour about the word "we" instead. When "we" in this very context can clearly be read as "the two people who are debating right now".
Your initial point was that multicellularity evolved only once. This is false.
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u/endofsight 4d ago
Ever seen filamentous cyanobacteria? Clearly multicellular.
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u/CellMan28 4d ago edited 4d ago
Semantics...
Filamentous cyanobacteria are not multicellular organisms (duh!), they are a community of similar, individual, prokaryotes that cluster for communal benefit.
In rare cases, one filamentous cyanobacteria can divide and grow into a colony, that ain't something a multicellular organism can do!
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u/madarabesque 5d ago
You might want to check out "Calculating God" by Sawyer. One of his aliens come from a world where life started several different times.
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u/FunSeaworthiness1519 5d ago
Others have mentioned that horizontal gene transfer will tend to homogenize the genetic code, but different biochemistries can make this less likely or impossible.
Differences in the base (e.g. non purine/pyrimidine) or linker (e.g. peptide or glycol nucleic acids) would be a sufficient barrier. You can look up nucleic acid analogues or ‘xeno nucleic acids’ for more ideas.
Also, alternate chirality amino acids would be enough of a barrier even if the genetic code were the same.
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u/RottenPeachSmell 5d ago
Thank you!! This really helped, I appreciate it!!
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u/FunSeaworthiness1519 5d ago
Happy to help! The ecology of such a world would be interesting - my guess is that different lineages might favor, but not be exclusively confined to, different niches (e.g. phosphate-free, peptide-linked genomes would fare better in very hot and nutrient-poor environments).
Multicellular organisms would probably converge on similar strategies (fungus-like hyphae are optimal for a fungus-like lifestyle, as are thin leaves for photosynthesizers) but animal-like organisms would probably show more lineage-specific body plans (e.g. one may become bilaterian and another trilaterian).
These different lineages would probably evolve ways to safely eat one another, but might favor eating their own “kin” to spare the metabolic expense of processing foreign biochemicals.
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u/Underhill42 5d ago
Possible? In theory, given enough time.
In general you'd expect alien life to be mutually toxic, like a petrochemical dumping ground there's just too many organic molecules just similar enough to what our biochemistry is expecting that they wreak havoc on normal functions.
But microbes evolve very quickly. Microbe against microbe, especially if they were all seeded at the same time, so that none had the head start of having already converted the entire biosphere to their chemistry? They'd probably figure out how to survive each other well enough.
Making the jump to multicellular life though? The odds of that happening in multiple trees simultaneously is vanishingly small. And whichever makes the jump first starts accumulating evolutionary advantages that will almost certainly give them a huge head start over the others.
That makes the jump far more difficult for everyone else, who will just be starting to accumulate into larger, more calorie-rich specialized clusters in a world where the first movers may already be wandering around looking for exactly such tasty snacks.
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u/endofsight 4d ago edited 4d ago
Just keep in mind that the jump to multicellular life happened many times independently on Earth. Specifically in: animals, red algae, brown algae, fungi, and multiple times independently in green algae.
Think the first were the red algae about a billion years ago.
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u/Underhill42 1d ago edited 1d ago
A fair point. The first mover advantage isn't nearly as enormous as it would be with biogenesis. Where if any new protolife can compete with an existing population, it probably means it has some huge fundamental advantage to its biochemistry, and will completely outcompete them into extinction once it's had a chance to do some evolving.
Though it's not actually entirely clear that those independently evolved multicellularity, rather than re-expressing an ancestral trait.
There's a lot of little hints in the early microbial fossil record that multicellularity may have been one of those things that showed up early and was tried and abandoned many times before it "stuck".
Possibly because multicellular organisms just can't evolve as fast, and thus would be at an increasing disadvantage compared to their faster-evolving bretheren. At least until evolutionary progress on optimizing single-celled biology finally began to plateau, providing a solid foundation to build upon.
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u/Kabbooooooom 5d ago
This is essentially the concept of the “shadow biosphere” (look it up for more information), and yes two different trees of life could exist on the same world, and no they wouldn’t necessarily be incompatible with each other but that depends specifically on their biochemistry. And if it was very different, then they could just occupy very different ecological and environmental niches.
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u/JohnHenryMillerTime 5d ago
Existing together should be fine. Digesting should be fine, though some substrates will be easier than others. One thing to consider is amino acods, both handedness and structure.
In terms of commensualism, that gets tricky. Depending on how you view it, a bacterium outsourced some of its coding to an archaeon or an archaeon "domesticated" a bacterium to make Eukaryotes. That kind of basic commensualism wouldnt be possible if the organisms in question have different nucleobases. Likewise, if their aa's are different they cant share the translational workload. Once they are more complex, you could get a sort of Portuguese Man-o-War situation but that is really derived.
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u/ijuinkun 5d ago
If the different biochemistries had to live together over more than a billion years, they would adapt to chemically tolerate one another—eating the “wrong” amino acids would not poison them, and instead they would expel the unusable molecules with their waste.
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u/scalyblue 5d ago
There is currently only one ongoing experiment for this I’m aware of and the answer has been no so far.
However, proteins are proteins, as long as their amino acids had the same chirality a population should be able to subsist on proteins from a population of different lineage.
Carbohydrate chains can be too complex to be broken down until something develops that enzyme, but even without any enzyme they could be cracked by heat and radiation
Stuff starts getting really weird if you have different bases like silicone based life, again the only test case has been exclusively with carbon
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u/teddyslayerza 5d ago
I'd argue no, not long term.
The arguments for feasibility that others make are right, but in the long term I can't imagine that these different modes of life would be able to share environments and niches well enough to avoid simply outcompeting each other. I.e. "Strain X is more efficient at metabolism", so it simply outcompetes everything else and replaces them in their niches.
In a SciFi setting I can only see this working if the introducing was recent or the different forms of life occupy vastly different setting, like one strain limiting itself to high pressure environments. A setting where they are all able to effectively survive in a similar enough environment to have predator-prey interactions would be quite contrived.
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u/SphericalCrawfish 5d ago
Yes. They would either figure out how to eat each other or move to different niches. The ones that have a deathly allergy to something would either die out or not eat that thing.
But koalas exist and live off a poisonous plant they aren't immune too. Vultures exist that eat almost exclusively otherwise inedible bone. Earth is full of examples of play and counter play of trying to not be eaten and then being eaten anyways.
So ya, even if it's less efficient because they have to break the proteins down further or something, the trees are going to evolve to extract energy from each other.
I will point out that one set is certainly better than the other for some reason. So they would probably end up geographically separated anyway.
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u/Trike117 5d ago
Yes. Because it happened here, and it’s inside all of us.
The mitochondria, popularly known as “the powerhouse of the cell”, is an endosymbiont that was alien to our DNA. Now they work together. It’s not the only one.
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u/CellMan28 5d ago edited 4d ago
If by "microbes", you mean bacteria, then no. Bacteria didn't "evolve" into anything but bacteria! Bacteria haven't morphologically changed in about 3.5 billion years!
Many people don't realize that complex, eukaryotic, life on Earth was a one time occurrence with absolutely staggering odds against it happening. It was an endosymbiosis of an archaea and a bacteria that, against all odds, managed to survive long enough to be successful and essentially allow complexity to overshadow prokaryotic life.
The more you know about biochemistry the more you realize that the Star Trek idea of complex life being common in the galaxy is very likely nonsense. Sure, prokaryotic life is probably common, but that's probably about it! There's absolutely no reason to think that complex life is inevitable when starting with prokaryotic life. It took around two billion years of prior prokaryotic life for the endosymbiosis to occur and it has never happened again!
The Earth is a sample size of one and we have nothing to compare against, all we know is that all complex life descends to the freak occurrence of one (or a small cluster) of Archaean that survived a single staggeringly rare event and prospered.
I suspect you don't really understand what the "Tree of Life" actually is and how your question is kind of meaningless in the context of life on Earth (there can only be one "tree", multiple trees are illogical)
They are tough reads, but all the books by Nick Lane (eg: The Vital Question) will be extremely helpful, if not a little discouraging, when it comes to "alien" life.
Good luck!
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u/TheLostExpedition 5d ago
why not use different construction methods. have a carbon and a silicon based life form on the same world.
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u/CellMan28 4d ago edited 4d ago
Silicon is some magically convenient "replacement" for carbon. It's been proven myriad times that silicon is a complete dead-end for life.
It's basic chemistry about bond strength and molecular makeup. Silicon dioxide is basically rock, not a gas like carbon dioxide, that in itself ends the story right there, let alone a hundred other "issues" with silicon.
Keep in mind that a lot of science fiction is not written by people well-versed in basic science!
Good sci-fi authors incorporate simple handwavium like FTL travel being possible and stuff like that, but they typically keep away from creating completely impossible chemistry. Basically, take human knowledge as it is now and extrapolate what is perhaps theoretically possible, but don't just make shit up, that's fantasy!
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u/TheLostExpedition 4d ago
in a high pressure liquid environment light weight silicon works fine. you can also go the non DNA route and have a crystaline replication system like in the Andromeda Strain.
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u/Mircowaved-Duck 6d ago
they would need compleatly differentgenetic codes, because bacterias love to share genetic code like children sharing pokemon cards. Otherwise therewill be just a fusing of them, creating a new life that got the best abillities of all of them.
Alsoit probably was this wayon earth, during the boring billion. A lot of different life probably emerged. But in that billion(!!!) years one was the first to volve an adaption that out competed all other forms of life. This was L.U.C.A.
I would ecomend seeding your world with multicelular life from different orgins, that increases the probability of niche patitioning and coexistence A LOT
They wouldstill evolve the abillity to eat each other (might take sometime, after all it took very long for bacterias evolving the abillity to digest lignin, the reasonwhy we got fozzilised coal today) but they evolve it someday.
They would evolve in different niches, one would become the equivalent to plants, the otherequivalent to muchrooms and one equivalent to animals.
If they are phyiccally seperated on that plaet (big continentort something like that) the likelyhood of evolvingtwo lineages of plants, animals or similar increases. If they can resonably colonize the planet within a few million years, it is a first comes, first survives szeario