Evolution of Early Planets

I think photosynthesis evolved before the first eukaryote (but not by much)
Also thermosynthesis produces oxygen just like photosynthesis iirc, so that could produce oxygenation events too.

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@tjwhale I recall the decision was a while back that gameplay would be too limited without the nucleus plus the ER and golgi. If you guys are interested we could start a thread on the viability of the prokaryote phase and consider adding it in (I’d support adding it in).

@crodnu Do you have any links for thermosynthesis? I haven’t been able to find anywhere explaining what the chemical process for thermosynthesis would look like. Also, something I left out of the original post to not complicate it but is also interesting to consider is that photosynthesis actually did evolve a bit earlier but did not use carbon dioxide and produce oxygen in its first iteration. Oxygenic photosynthesis only evolved a bit after that, and that led to the great oxygenation event.

Also now that I’ve written out the whole original post and had time to think about it, I think we can break it down a bit more. The only real given to the Model Planet is:

  • Initial period of intense volcanism and meteor bombardment
  • Formation of an atmosphere of carbon dioxide, methane, ammonia, and other gasses
  • Formation of liquid water oceans
  • Accumulation of organic molecules in the deep ocean and around hydrothermal vents
  • Beginning of simple prokaryotic life metabolizing the minerals and organic molecules of the deep ocean

Anything past this is variable. Maybe photosynthesis will evolve and lead to an oxygenation event, or maybe not. Maybe photosynthesis will evolve but not the oxygenic kind. Maybe oxygenic thermosynthesis or oxygenic chemosynthesis will evolve (not sure if that’s possible). Maybe the oxygenization of the atmosphere will lead to different outcomes on different worlds.

i got the formula from the old forums, but maybe they were a placeholder?

also, the great oxygenation event happened 2.45 billion years ago and the eukaryotes appeared 1.6–2.1 billion years ago (both dates according to wikipedia).

How would it affect gameplay? They don’t really do anything from the players perspective. If we allowed prokaryotic cells to use pilli and flagella, then they could scavenge and fight, it would be pretty fun.

I think the 0th iteration for prokaryotic gameplay could be literally to just allow cells, as they are currently, but with nucleus + er optional. That’s really not a big change but get’s us along way.

@crodnu I checked the post and saw it was actually me who had posted that, but that was me just copying the formula for photosynthesis but swapping in heat for light (which is wrong). I’m not actually sure what the theoretical chemical process for thermosynthesis would look like.

@tjwhale I posted some of my thoughts over on the prokaryote thread: Prokaryote Gameplay

Vary concentrations of each to vary it. Less free organic molecules wold either slow progress, or make a hyper-competitive scenario. or the opposite, lots of organic molecules make fast progress that reduces importance of photosynthesis.
Too fast/slow; maybe check the growth rate? if it’s to fast or slow, try to reign in the outliers. We don’t want to make it TOO easy and thus, boring.

In your research (great work on that, BTW), i think you forgot to mention that earth’s first atmosphere (mostly methane) got blown off by solar winds. Also, fomration of the Moon blasted eerything, and made a moon. Major things missing? I don’t think so, you were pretty thorough.
I wouldn’t say ENTIRELY open-ended, or poodoo can hit the fan very hard. Like asteroid killing off the players entire species. I think we should always allow a CHANCE (even a small one) for recovery.

We could switch up the molecules used, change biology on a fundamental level. Mathane-based biology on a frozen world (instead of H2O), or breathe methane instead of O2 (They’ll love cows and pigs), etc. Little, plausible things that change how biology works to be based off a similar chemical.

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The plan is to have compound concentrations in for 0.4.0 so I’m excited to refer back to this thread.

It is? Isn’t the problem still that the player spawns randomly so the biomes can’t be differentiated. I think it will be a while until we get the editor support etc. required for differentiated biomes.

Not that, though that’s in the code already, I mean the compound concentrations going down over time (refer to @tjwhales post about his decisions)

The code already supports 02/c02 percentage variance and compound concentrations though)

Oh right. that. But still even if the concentrations can be tweaked, they shouldn’t as the spawning is random. And btw I can’t seem to generate any ATP even though I have full glucose (the environmental oxygen doesn’t actually seem to work).

Process system needs to be written to work with the new stuff :slight_smile: I was surprised even cell growth worked. I could get that working instead of health tonight if you want.

Tjwhale also wanted a lot of changes to that.

Since we’re doing patch differentiation in this update, I’m wondering whether we’d be able to get some of the features from this thread into the next update. I think some of these features would greatly help in giving life to the game and will also hopefully be easy enough to include in the current workload. This would be in the form of two behind the scenes events that occur that affect environmental stats:

Event #1: Origin of Life
Triggers on the first generation of gameplay.

  • Free floating Glucose, Ammonia, Phosphate, Iron, and Hydrogen Sulfide levels drop by 80% over the course of 3-5 generations. This represents all of the free floating nutrients getting eaten up by multiplying microbial populations.

Event #2: Great Oxygenation Event
Triggers 3-5 generations after the first species evolves either Thylakoids or Chloroplasts. If a second species evolves Thylakoids or Chloroplasts, the timer reduces by 1 generation.

  • Free floating Glucose, Ammonia, and Phosphate levels drop by 50% over the course of 3-5 generations. This represents the creation of a planetary ozone layer, which blocks the intense solar radiation that was generating glucose, amino acids (in our game represented as ammonia), and nucleic acids (in our game represented as phosphate) in surface water biomes (like ocean surface, estuary, and tidepool).
  • Oxygen levels increase from 0% to 15-25% on surface water biomes (such as estuary, ocean surface, or tidepool). Oxygen levels only increase to 1-2% in biomes any deeper than that (since oxygen does not dissolve that far down).
  • Iron and Hydrogen Sulfide levels drop by 95% in surface water biomes. This represents the oxidation of these nutrients (for example iron reacts with oxygen to form iron ore and sinks to the ocean floor). In deeper biomes, Iron and Hydrogen Sulfide levels drop only by 20%, since less oxygen dissolves to these depths.

The above features require that the game start with only one, 1 hex prokaryote species as planned. Also note that the percentage drops are multiplicative not additive (so final glucose levels would reach 10% of their values at generation 1 if both events occur).

If you want to read the science behind these events, read the OP.

I think these features can greatly add to the gameplay. When you start the game, fermentation is your only energy source. At the moment, it’s almost a no brainer to go for metabolosomes first, which I think is both a little boring gameplay wise and not very realistic. This makes it so that life diverges into different paths (aerobic vs anoxic, chemosynthesizing vs photosynthesizing, etc.) as well as upping the difficulty as the game progresses because the free floating nutrients begin running out.


Yeah nice ideas.

Re nutrients becoming less available we’d need to balance it with how well the species can spread out to make sure they have a chance to make it to the surface.

It’s interesting I had a look to see what you could do at 0% oxygen and you can still use cytoplasm, thalykoids, nitrogenase, chemosynthesizing proteins and flagella. If we took the oxygen requirement off rusticyanin you could use that too (not sure how everyone feels about that) and when we put the pilus in that would be available. So in a world with 0 oxygen there would be quite a lot of choices available.

It’s nice too as it means the surface regions of the planet will be quite different from the depths, which will differentiate things nicely.

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I already mentioned something like this in the Discord a while ago, but I suppose it’s relevant to this thread so I’ll rehash it here. Sorry if it’s a bit of a mess, I’m mostly throwing random thoughts together at 3am so please bear with me

I had a few questions and concerns about how evolution works in response to events and such:

For instance, as oxygen levels rise due to photosynthesis, what’s stopping nearly every previously anaerobic cell from independently adapting metabolosomes? Oxygen is toxic to obligate anaerobes, so realistically you’d expect an oxidation event to weed out the vast majority of these species, save for those still in oxygen-poor areas and those who were lucky enough to evolve some way of dealing with the increased concentrations of oxygen, which iirc is what happened on Earth.

But according to my current understanding of how auto-evo will work, basically every cell, eukaryotes included, would end up evolving metabolosomes sooner or later because they’re easily available in a single generation and, in a world where the air is slowly killing you, are easily one of the best choices for avoiding extinction. Perhaps a few very unlucky species would go extinct, but the majority would survive.

Wouldn’t it make more sense if aerobic proteins are something that are only evolved once or maybe a few times, (including by the player for gameplay’s sake of course) that all aerobic cells would then be descended from? (partially including eukaryotes with mitochondria)
Weren’t eukaryotes anaerobic until mitochondria came along? I think oxygen-producing photosynthesis only really evolved once on Earth, in cyanobacteria, but what about aerobic respiration?

How do we lock the majority of species out of a certain adaptation without it feeling artificial or making it equally hard for the player?

I’d also like to bring up some things about endosymbiosis too.

How would an anaerobic eukaryote manage to even be in the same environment as an aerobic “proto-mitochondrion?” Wouldn’t the oxygen that the aerobic bacteria thrive on be toxic to the eukaryote? Or would it happen in some sort of in-between zone, where the oxygen is enough to maintain the populations of aerobic bacteria, but not enough to kill the anaerobes? Or would the anaerobes evolve some way to tolerate the oxygen? How would that work?

Also, if a eukaryote already has metabolosomes, what realistically is stopping it from adapting and specializing those metabolosomes until they’re as efficient as a mitochondria?
Would it make sense for mitochondria and such to start out as effective as one or two metabolosomes, and the player could specialize them and make them more efficient?

Would it be an interesting mechanic if, instead of unlocking “mitochondria” or “chloroplasts” based on what cells you engulf, you got the actual cell you engulfed and can place it in your cell as an organelle, and could modify and improve it?
What if you assimilate a cell that already has an endosymbiont?

Obviously stuff like this is pretty far into the future and we don’t really need to think about implementing any of it just yet, but it could be useful later on as we try to figure out how to accurately represent evolution.

Interesting question, I have no idea. I guess maybe one possibility is that the eukaryote was aerobic but just not very good at it. That would mean the proto-mitochondrion could live in the same environment, live inside the Eukaryote without difficulty and be a huge boost to the Eukaryote. After the endosymbiosis the Eukaryote then loses it’s own respiration proteins because it’s more efficient to rely on the mitochondria. Though that’s a total guess based on nothing.

Quite a lot of people talk about this and it sounds interesting. I guess there’s not much difference. In the sense that adding a symbiont to your cell which has 2xmetabolosme is just the same as adding 2xmetabolosme next to each other. I guess maybe there’d be a bit of internal membrane too. If you edit the symbiont by adding a vacuole or something wouldn’t that be the same as just adding a vacuole next to it, would there be any gameplay difference?

It might not be so hard to implement for realism’s sake.

Firstly I think, for AI species, it would be quite easy to weight the auto-evo system so adding more of the structures you have is common, adding a new one you haven’t had before is rare. So if we wanted all cells with chloroplasts to have one or a few common ancestors we could do that I think if we wanted.

Re changing O2 concentrations I’m not such a fan of having the change be too dramatic. I think we want to avoid making an anaerobic stage followed by an aerobic stage because that means making 2x the content and that you can’t mix and match the different systems together. I’d rather have 1 stage where all the organelles worked all the time, it’s just that maybe near the beginning the aerobic stuff is weak and near the end it’s stronger.

I think our dev resources are so, so, limited we need to spend them as efficiently as possible.

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You forgot about aerotolerant organisms, which can’t use oxygen but can tolerate it, mainly by using enzimes that neutralize Oxygen’s toxicity, so it would feasible that an anearobic organism found an aerobic cell in the same patch.
Also, metabolosomes are supposed to be more efficient the more oxygen is around, so in a patch with low oxygen they wouldn’t offer a bigger advantage than gycolisis for example, making it less likely that species with them could thrive there.


I think another interesting question on this topic is “how similar should each Thrive playthrough be to Earth?”

On one end of the spectrum every game has a planet which starts out with the soup of compounds, then has anerobic life, then photosynthesizers turn up and has a GOE, then endosymbiosis happens and then multicellular life emerges. I think the Earth has been a frozen iceball a couple of times too.

On the other end of the spectrum would be a much more open space where things can happen in different orders or not at all. Like maybe complex life emerges without endosymbiosis. Maybe there is a high oxygen period followed by a low oxygen period. Maybe eukaryotes evolve 6 different times or something.

I’m not sure how everyone feels about it, we can have it be very prescriptive and linear so it follows the Earth very closely or we can have it very open or something inbetween.


Options, which could also be part of s difficulty setting.

As an example you could have the options of earthlike, semi random and full random. So it let’s the player choose what experience they want.

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I think it’s a good idea to bring this thread back up as discussion surrounding environmental tolerance adaptations mature a bit. It would be beneficial to have a shared understanding of how the player’s planet on an average playthrough will develop, as the player’s environment will have a dramatic influence on progression and other mechanics. I think a good amount of theory is present throughout the forums and this thread in particular, so I won’t dive too much into background information as I tend to do.

I will disclose that I am interpreting an average, “normal” setting of a Thrivian planet to largely reflect Earth’s geological history with some deviations. We can discuss variation when we better understand environmental tolerances, the “normal” playthrough, and when planet generation stops being cursed as a feature.

The Evolution of Compounds

Let’s first think of this topic through compounds, which represent the resources and niches a player has available. Looking at Earth’s history, the various compounds included have a generally predictable pattern influenced by natural developments on a planet.


  • Iron – Iron can be very prevalent on an early planet, but could slowly become less and less common as oxygen is introduced to the environment. Eventually, iron will likely be limited to the depths of the ocean.
  • Hydrogen Sulfide – Hydrogen sulfide will likely share a similar story with iron – predominance over most biomes, then gradual reduction with the introduction of oxygen. Hydrogen sulfide would probably be the most important compound in the beginning parts of the Microbial Stage.
  • Glucose - Glucose already changes through a playthrough, reducing throughout time as a representation of reduced free-floating organics.
  • Phosphate – Phosphate could probably reduce a decent amount as more and more organisms show up and utilize free floating organics, but not to the same extent as glucose. Local events, such as runoffs, volcanic activity, and more can temporarily increase the concentration of phosphate within local conditions.
  • Ammonia – Similar to phosphate, ammonia could reduce a decent amount as more and more organisms show up and utilize free floating organics, but not to the same dramatic extent as glucose. Local events, such as runoffs and volcanic activity, can temporarily increase the concentration of ammonia within local conditions.


Oxygen – The most dramatic example of an atmosphere evolving, oxygen will introduce itself to the planet through the biological activity of photosynthetic life. It might be beneficial if oxygen cannot dip beneath a certain concentration if it reaches certain checkpoints. For example, once oxygen reaches 3% on the surface, it cannot go below 3% no matter what, it cannot go beneath 6% once it reaches it, 9%, etc. This will ensure that the game doesn’t crap out and destroy the playthrough since it is so important for advanced morphologies.

Oxygen will first be largely limited to the surface patches, but will make its way down to the deepest parts of the ocean around early multicellular (ocean depths became oxygenated relatively recently).

  • Nitrogen – Nitrogen likely was present at a lower level than what is now seen on Earth. The maturation of the nitrogen cycle as well as the evolution of plate tectonics has resulted in an increase in available nitrogen, until it reached modern levels.
  • Carbon Dioxide – Carbon dioxide was likely more present on a young Earth than it was now. It is believed that carbon dioxide lowered somewhat as time went on, though obviously not to an extreme extent.
  • Sunlight – The atmosphere was rather hazy on young Earth due to the presence of methane and ammonia, volcanism, and the lowered rate of oxidation due to, well, a lack of oxygen. The beginning of a playthrough can have slightly less sunlight available on average, but this can trend towards normal conditions rather quickly. The early level of available sunlight can be an environmental factor that varies a lot from playthrough to playthrough.
  • Temperature – The oceans were much warmer on a young Earth, though this period of heated waters didn’t last very long – otherwise, a lot of Earth’s water might have evaporated and have been lost through a weak atmosphere.
  • Salinity – Earth’s oceans were likely less salty at first. Considering the lack of variety on salinity in the Microbial Stage in Thrive, I think it would be fair not to have salinity vary immensely throughout a playthrough.
  • Pressure – Pressure shouldn’t dramatically alter itself throughout a playthrough, though different planet generation settings can have average depth be a tweakable factor.

As a Whole, How Will The Climate Evolve?

I think that we should have environmental compounds be rather unstable and volatile to a dramatic extent at the beginning of a playthrough for multiple reasons…

  • Young planets don’t have stable biogeochemical processes established.
  • Introducing variations in the early game can be a relatively easy way to increase replayability. Players might have to rapidly pivot evolutionary strategies, which would be easier to do considering the simplicity of the organisms at this stage of the game.
  • The lack of other complex organisms results in a lack of a notable threat in the beginning of the game, so the environment should probably serve that role at first.

Currently, I think the average playthrough will follow this cadence…

  • Hectic, Chaotic Beginnings – The beginning of a planet’s history is characterized by unstable biogeochemical processes and intense natural events, such as bombardment and volcanic activity. Compounds will fluctuate dramatically with little rhyme or reason, and atmospheric concentrations will similarly vary. The environment as a whole is a threat to be paid attention to. To reduce the burden of this fluctuation on new players, hydrothermal vents can reduce less extreme swings in concentrations, and would generally be sheltered from the most severe of environmental events. These might be the first 10 or so turns in the average playthrough where compounds could genuinely go from being extremely prevalent to incredibly sparse within a patch.
  • Initial Stability and Slight Increase of Oxygen – Compounds fluctuations will eventually slow down into more settled numbers with some variety, and the frequency of environmental events will reduce. This is where we can start seeing some of the compounds trends mentioned above. Oxygen will start to build up near the surface, introducing hints of the most powerful respiration strategy in Thrive and allowing players to begin adding some complexity. This will help players feel secure enough to start somewhat specializing around their niche, allowing them to build up to performing endosymbiosis. Compounds might still fluctuate, but not to the dramatic extents seen before.
  • Snowball Earth(s), the Upsetter – Glaciation events can serve as an immense challenge placed on the player, reducing the viability of photosynthesis, shaking up food webs, and forcing players and AI to adapt their morphology. We would probably want to introduce controls to have it so that oxygen can’t just disappear completely once it shows up to not completely screw over the player, but the rate of oxygen production will likely slow down for a certain amount of time. Snowball events can occur multiple times, though we might want to consider making it so that later snowball events are less harsh than earlier snowball events.
  • Oxygenation and Stability – Eventually, oxygen is introduced and the atmosphere and environmental concentrations generally settle around certain levels. This will allow players to develop strong eukaryotic capabilities and eventually attempt to become multicellular. Environmental events may still happen, but to less of an extreme.

I think what this cadence will ultimately stress is the role of oxygen in relation to progression. Since oxygen has the most powerful form of respiration in the game, it is likely that that most players will trend towards adopting oxygenation respiration as a strategy. This is okay since the vast majority of complex, multicellular life as we know it is dependent on oxygen. But having oxygen also have a strong impact on the atmosphere will also provide a sort of rhythm for the player to understand; when oxygen arrives, compounds start shifting dramatically. Therefore, variation in gameplay can be tied to the nature of how oxygen is introduced.


Great that someone put this to writing. It would be great if we could get some input from our @Theory team about this.