Could an autotrophic civilisation develop, or will evolving life forms always eat each other?

Question

I can imagine our own civilisation becoming autotrophic eventually, if biological life gives way to a population of machines that need only sunlight. However, the history of that situation still involved a long period of organic life forms eating each other.

---

So my question is about an organic evolutionary history with only autotrophic organisms, that still leads to civilisation.

I'm imagining a world in which organic life forms evolve to gain energy from light/other radiation/heat/chemicals in the environment without any of them ever evolving to gain energy from eating other life forms. That is, an entire evolutionary history without any of the life forms eating others.

I see two potential obstacles to this:

• Without the increased complexity of competition involved with eating and being eaten, and the far higher energy density available, intelligence may never emerge.
• Even if the emergence of intelligence is possible that way, it may be impossible to have a large varied population without the spontaneous emergence of organisms that eat others.

I'd like to know if there are natural situations in which these two obstacles would not apply (naturally - not in the form of an overseeing species that tends the life on a new world to remove heterotrophs). I'd also like to hear about any other potential obstacles that I should take into account if this autotroph world is to be believable.

Since "civilisation" is subjective, I'm looking for a world that has developed to the point of having at least one species using learned language to communicate and record history.

---

To clarify, I am looking for a natural evolution from scratch, not asking about machines. The introductory paragraph shows a simple example of a population ending up autotrophic, to contrast with my goal of a population that has always been autotrophic, right through its evolutionary history.

Also, the environment need not be Earth-like. I'm looking for environment/conditions under which this might be plausible. So if the limited amount of energy on Earth is a restricting factor, could it still be possible in a very different environment with much more available energy?

Answer 1

I don't see how the situation you suggest is possible. As soon as one species develops the ability to consume another it will have a massive competitive advantage since animals are a denser source of energy than plants which are a denser source of energy than sunlight.

In other words you would need something pretty massive in place to stop the evolution of consumption. The Giant's Trilogy (James P Hogan, good trilogy, I recommend it) has an alien world where all animals have evolved a way to be incredibly toxic to each other. This means that they are all herbivores as no carnivores evolve, but even there the animals eat plants.

Assuming it did happen though then competition would definitely still emerge (just look at trees in a forest jostling each other for light for example). Intelligence is much harder to justify though, there is a huge energy cost in running a brain and so the gains need to outweigh those costs. Plants are not mobile enough to need much intelligence, and sunlight is not a dense enough power source to give them much mobility.

Answer 2

life in abundance produces competition. Go to any forest, (it's more obvious than a prairie) you can see the trees and other plants all fighting to get their share of the sunlight.

And plants have fungus and bacteria that attack them.

Maybe if one thing only eats something else after it has died? because you will need something to eat and 'decompose' the dead or you everything will just die and take up space, or the life forms never die. I think right there is the major problem, what happens to the dead? And once you have something that eats the dead, what stops them from starting on the feeble? or making them sick/feeble?

Answer 3

You might see this if life somehow evolved in extremely high radiation. Either much closer to a star, or around a much hotter/brighter star.

Then it might be possible that energy storage actually ends up being less efficient than simply getting it from the environment. So autotrophs would have the advantage, and "eating other things" wouldn't really make sense. Competition would be competing for raw energy collection, which might involve combat but lifeforms wouldn't be eating each other for energy. This would provide the potential impetuous to develop intelligence.

You will likely need something to at least break down other things for the raw ingredients, the "what to do with the dead" question that other answers have brought up.

Answer 4

Plants are out. Even if you increased the efficiency of photosynthesis to the point that a plant could think and run around, there would be no reason for it to. Sunlight is the same everywhere within reasonable walking distance, so there is little incentive to move, especially when you have to be huge to expose enough area to the sun.

Chemotrophs could work though. With the right conditions they could behave much like regular animals - they just happen to eat rocks instead of plants or other animals.

Single celled life

Start with the necessary chemicals bubbling up from underground. When this happens, small organisms reproduce rapidly, feeding until there is no usable energy left and the rock has been reduced to a fine dust.

Wind picks up the surface layer of dust, and a few survive long enough to be blown to a new deposit, where the cycle repeats.

Early evolution

Mobility would be an advantage in this environment - first to simply move to denser energy sources faster than the competition, but also to make it to the next food source. Some would grow wings to more easily catch the wind and be carried further. Others would grow legs and store enough energy to be able to walk a useful distance into the desert. Most would still die, but the slightest advantage is enough to get evolution going.

You could also have trees, extending roots down to get at chemicals deep underground. The bacteria can't do that if the reaction also requires something from the air.

Complex organisms

Walking around works best with an internal digestive system, so these creatures would probably lose the ability to simply sit on a rock and absorb it. There are a couple of ways it could work.

• All the cells could retain the ability to use the original energy source. Digestion just means separating it from the ingested rock and getting it into the bloodstream.

• Cells are more specialized to the point of being similar to regular animal cells. Stomach bacteria convert the rock and air into organic material that can be digested in the normal way.

The creatures would grow larger, because that makes it easier to walk long distances between food sources, or to fight off any competition once you get there. This isn't necessarily a peaceful planet - nothing worth eating is quite different from nothing worth killing.

Intelligence

With larger creatures it is possible to have a large brain without using too high a percentage of the available energy.

Evolving intelligence would be a definite advantage. Recognizing the geology that is likely to mean a fresh energy source nearby. Tool use to dig through the dust and uncover deeper deposits without waiting for them to be exposed naturally.

Civilization

Mining takes the place of agriculture on Earth, allowing the people to settle in one place and develop a civilization. Depending on the chemical reaction used as the original energy source, it may be reversible once the civilization can use fire or another external energy source, which would make it even easier to grow a city.

Removing heterotrophs

Avoiding the development of predators (or even mushrooms) is harder. Life has a way of filling every niche there is.

I don't think toxicity will work. For just about any toxic substance you can name, there is something out there that will happily eat it.

Energy density is better, but not perfect. The initial bacteria can be efficient enough that almost all of the material they take in is converted into an unusable low energy form that isn't worth eating, but once the original food supply is exhausted, being able to feed on what's left would be a huge advantage.

Limiting heterotrophs

It might be possible to limit heterotrophs to lower life forms if there is generally not enough extractable energy in animal cells - fungi growing on a carcass is unavoidable, but chasing down prey to eat is never worthwhile. The concept of heterotrophy would be familiar, but a civilization of humanoid mushrooms would seem very alien.

Earth type life evolving independently is also a possibility. You could slow that down with active geology that is helpful to the chemotrophs until they start trying to build cities and a shortage of liquid water.

Stable civilization requires the planet to quieten down a bit, so life as we know it will still evolve, but the chemotrophs have a billion year head start - They are building a civilization while everything else is still limited to single celled organisms.

Answer 5

Realistically? No.

But as far as world building goes I think you could do it by taking Tim B's answer as a basis: Extreme toxicity, but then of course in the plants themselves. Now he claims that there is no reason for the plants to develop mobility and/or intelligence, but all you need for that is a more aggressive planet. The most peaceful option would for example be a huge planet with an extremely strong star and a very dense set of clouds with holes in them moving extremely slowly (no idea what the correct name for it would be, but we have them here on Earth from time to time, so creating a world where they are far more common would be doable) and give a huge advantage to a 'plant' moving along with the hole. Even better this would lead to more and more fighting between the 'plants' to stay 'in' the hole and even though they can't eat each other, this will still cause a nice amount of competition and as cloud coverage isn't exactly constant it can lead to a bit of diversity (e.g. the mobile plants develop in the desert where holes are constant, whilst around mountains you get more traditional plants). So what is the weak point in all of this? You probably can't make a plant toxic to all other organisms. Still though, world building has never been about perfect realism, it's about creating believable worlds and for that the idea of toxicity is perfectly adequate. The trick is just in thinking up a scenario where competition and murder will become worth it.

Either way, given the above you would then allow these 'plants' grow more powerful and bigger and bigger. These bigger, stronger 'plants' would overtake the 'dumber' communities that exist in places where the cloud coverage isn't as bad. Here they would very slowly develop till they figure out ways to disrupt the flow of the clouds using some kind of combined effort which would allow the creation of villages in the rest of the world as well.

An interesting alternative to sunlight would be organisms fighting for heat from an active core of a planet. There are deep sea communities which live near underwater volcanoes that function like this. Still I think it's harder based on that to build a full ecosystem, but just maybe you could use it as a foundation for some more diversity in the previously described ecosystem. As in, you could have lots of lava vents in the world and as there is no competition with photosynthetic plants most of the time they would be free to grow. Next the mobile 'plants' could murder whatever shape these communities take and build their tools out of them or something.

Answer 6

Read Ben Bova's Jupiter or Leviathans of Jupiter. For this science fiction novel he postulates that the storms and high densities in the upper atmosphere of Jupiter create a nutrient/food that is not a living entity. This filters down to the depths of Jupiter where the Leviathans have evolved (with intelligence). The leviathans eat only this "manna" like substance. In this story other creates eat the Leviathans, but you could easily take them out of the picture. Population levels would fluctuate based upon the availability of the manna. The Leviathans in the story reproduce through a process very similar to mitosis. So when food is scare they stop dividing. When food is plentiful the divide more frequently.

Any location that could support life, had sufficiently large source of energy and sufficient space could potentially develop life as you suggest.

Perhaps the right stellar nebular has bred intelligent life in this way. The energy demands of movement in 0-g and low-g environments is much lower and perhaps sunlight could be strong enough to support it.

Answer 7

For four years, I lived in the Amazon forest. Of all the environments on earth, you would think this to be the most likely to be the most closely autotrophic environment on earth, huge rainforest, just converting light energy to life sustenance. But it is the most violent place I have ever seen. I tell people that when a person walks into the Amazon, the jungle starts licking its lips. Even the native people's relationship with the jungle is one of nearly animalistic survival - consume the jungle or be consumed by it.

The soil in the Amazon is terrible. All the rain washes out the nutrients from the soil terribly fast. So when the native people clear out a plot to plant anything, they get soil that supports hardly any crops. So one wonders why the forest is so green. The answer is in a very fast, efficient, ruthless cycle of life and death. Plants and animals alike are constantly dying and the survivors consume as much of the nutrients as they can before the rain washes them away. And the plants are not just passively competing for light. They are actively killing each other and animals, so they may have more nutrients. Many of the plants will even inject chemicals into the soil, by their roots, to do away with competition, and when trees outgrow each other, they are only too happy to consume the loser's rotten remains.

So if the most likely autotrophic environment we know turns out to be the most perfect example of eat-or-be-eaten. I'd say the indications we have is that no matter which way you slice it, things will develop ways to eat each other.

Faxn and Quentin propose some plausible scenarios, but even there, I can imagine predatorial traits developing. Quentin shows the difficulty of removing or even limiting heterotrophs, and in Faxn's world, I can easily imagine that survivors at the edges of one of the catastrophic events might benefit from turning around and eating the dead or even other weakened lifeforms. Imagine if in Faxn's world, some of the lifeforms realize that if they run toward the danger warning, they will encounter a ready source of predigested energy. The danger warning becomes a dinner bell to predators - too tempting a possibility for life not to give it a shot.

Answer 8

I like the way you're thinking and would like to offer some reasons why the species may evolve. However, there is one thing I'm not sure about, but I'll get to that.

Competition

• You brought up a great point about competition being a factor in the necessity to for a species to grow and develop to the point you're speaking of. Even without the search for food, there's always something to compete over. If the planet were completely 100% autotrophic, and no life were to develop the ability to consume other life(even single celled organisms), then there will likely still be the need to procreate and therefore populate new land. Species might compete for land to support their populations, thus giving reason why they may evolve defensive and offensive abilities, as well as behaviors, strategies, and innovations to suit.

Communication

• I would expect that since they get their energy from the sun or heat or radiation etc, that they still would need a good source of water. They may never have orifices for any reason other than breathing, drinking, hearing, and scent(which would be for finding water sources and evading competitors). In fact, they may be able to absorb moisture through their skin like some reptiles and amphibians. This might limit their communication to skin coloration(much like the giant squid), physical motion, etc. rather than truly vocal communication.

Fire

• As many animals do, this species may get creative when looking for their needed energy sources(especially if they get energy from the sun/heat and seek more energy after sunset). This could eventually lead to an understanding of the dynamics of fire, and the creation of fire.

Higher Intelligence

• One of the greatest contributing factors to higher intelligence is the capacity for imagination. Imagination, innovation and creativity are closely tied together. If the species can be creative/imaginative/innovative, they can grow in that creativity and become truly sentient.

But...

• They don't consume matter, so their bodies have no matter to work with to grow or maintain itself. So, they would have to have some way to get all they need from minerals/chemicals. Even plants require some matter along with their sun air, and water. Seeds are packed with nutrients that the plant needs to begin the fulfillment of its potential for life. Where would these things start? What matter does their body use? Do they only absorb matter that is soluble?

Many questions, but still intriguing enough that I created an account to answer.

Answer 9

I think it might be plasuble for predators to never evolve. Here's an abstract template for such a world.

Imagine life evolving on a world that has frequent extremely destructive natural disasters, like meteors strikes or high intensity storms (or something more fantastical like spacequakes or phlebotinum shocks).

There are various ways life can evolve around such a pressure, but one in particular gets the result you want, spreading thin. Populations of autotrophs get as far away from each other as they can manage to increase chances that more of them are where the disaster isn't and thus survive to make a next generation. They evolve movement to facilitiate this spreading out, basic communication might evolve as a warning system, even if they are never fast enough to escape a disaster once it's detectable, if A detects a disaster and warns B b might be able to move father away sooner and thus live.

Now imagine a predator trying to evolve in this, your prey spread out to the farthest edges of their preception, and their first, most important communication is "danger! get away from here!".

Stopping carrion eaters is harder, plentiful corpses from the disaster would build up. This might be fixed by placing this whole thing on a gas giant. living things float, dead things fall the core where the pressure is too high for life.

Inteligence and socicity evolve from the shouted warnings of disasters, If patterns exist in the disasters being able to predict them is a huge advantage. Even just being able to describe the location of current storms better could help.

Answer 10

I'm going to break from the mold and say this is plausible; here is why:

Competition is not the only agency at work in evolution.  In fact, it isn't even a majority shareholder.  Most life-on-life interactions are either complementary or indifferent.  Few relationships are actually competitive.  Early scientists where not immune from injecting philosophical bias into their theories; people, in general, find it difficult to even notice, let alone understand, unfamiliar behaviors.  The idea the life in forest ecologies are competitive by nature is an example of just such an anthropic projection.  Sunlight is mostly anti-biotic and trees rush to fill gaps in the canopy to protect and nurture life in the understory, which in turn recycle the tree's waste.  Plants tent to only grow within their niche and few plants actively 'steal' food from others.  Hemlock grows slower than Douglas Fir, and as such spends much of its life shaded.  It does, however, tend to average a longer lifespan, the wood is hardier, denser and will, eventually, break through to the upper canopy.  Trees can still grow in shade/partial sunlight(albeit retarded), the main advantage of filling the canopy comes from protecting the understory, a completely symbiotic act.  Imagine a couple of big, old oak trees who have grown into each other and become entangled.  One person might look at this and 'see' them competing for sunlight and canopy space.  Another person, of a different altruistic persuasion, might 'see' them providing structural support for each other.  Many modern biologists have been attempting to trend perception of evolutionary mechanisms to reflect evidence suggesting that, in the game of life, altruism is the best, most used strategy.  Although any strat, so long as it's reproductively successful, can persist.  Intelligence, I'd contend, is more the product of reproductive selection than survivability.

However, this is an argument against competition in evolution is nearly moot when considering a completely autotrophic ecology (I felt someone had to be the voice of Kropotkin amongst all these Darwinists).  With this question, we're muddling about the thin, hazy ontologic boarder between what constitutes 'life' and 'non-life'.  Is life the process or the processor?  Or both?  Does it have to be cellular?  Can not any indefinitely sustainable chemical reaction be considered alive?  It's not simple to strictly separate 'organic' from 'inorganic' compounds in this respect.  We tend to think of life as being cellular, and when observing the cell we see a complex factory, self sustaining and replicating at the behest of thousands of decidedly non-autorophic, indeed heterotrophic processes.  For you to argue a completely autotrophic ecosystem, than you are most likely to describe non-cellular basis for life, molecular automatons, which would themselves hardly be recognizable as 'life', and might simply be dismissed as a wholly chemical, geologic, or otherwise 'natural' process.

Yet we yield, for the sake of the question, arriving at a civilization of intelligent beings after some process akin to evolution.  To do this we would accept beings of 'structural complexity', rather than 'chemical complexity'.  A very subtle distinction.  The main contention with your idea of a strictly autotrophic ecology is the build up of waste.  Excrement, shedding, carcases, and other materials must be recycled in some way, or else the entire niche might eventually suffocate.  If you're attempting some sort of 'living sand', 'living slime', or 'living smoke' I don't see how it would be distinguishable as 'living' without making some chemical alteration to its structure and strata.  Even then, the mechanism responsible for building/stacking is going to require fuel for motivation, a chemical reaction, or else we sorta deflate the meaning of the word 'food'.  To be truly autorophic we would describe some natural process which can recycle chemical(food) waste.

Because we have fuel requirements to attain locomotion for large organisms, these organisms would be an advancement of growth, rather than separable species.  That is to say, your beings are theoretically immortal, beginning life as something similar to lichen or slime mold, and growing into an intelligent, complex being.  I would imagine alteration in life cycle would lend to an interesting social structure.  The young are 'cultured', and grown as we humans would tend a garden.  Even so, we need some mechanism for the building/stacking of the 'organic' aspects and a way to distinguish where one sand monster ends and another begins, and what exactly differentiates them from their environment.  This is some form of life with a distinctly different chemistry than what we are familiar with on earth.  Think an ecosystem at home in the churning storms of a gas giant, or a very actively volcanic world, or something truly exotic living in a heliosphere, or within the probabilistic permutations of a black hole's compressed condensate.  Someplace where natural processes can fill in the gaps which would otherwise be filled by other organisms.

Careful, however, if we stretch the definition of life too far, than even the hydrogen atom could be considered alive!

Answer 11

It is not possible for an entire eco-system to be autotrophic. Eventually a mutation will allow a species to consume the other, and when that happens the consuming species will have a MASSIVE evolutionary advantage in the form of significantly higher energy densities ensuring that mutation will spread.

However, civilization doesn't usually refer to an entire eco-system, only the collection of sapient beings. You could therefore try looking at the idea of autotrophic sapients evolving in a world with other non-autotrophic organisms.

For this to be possible at all it would require MUCH higher energy density then the earths sun provides though. There isn't enough energy density to support active movement from the sun, and without that not much reason to waste further energy on a brain.

I don't think you can just move a planet closer to the sun either. Rather or not intellegent life can evolve so close to a sun and at such high temperatures implied by such is...a complicated subject that not everyone agrees on. However, it doesn't really matter, as no matter how much energy is available from the sun it's unlikely that sapients would evolve from photosynthesis. The problem is that with photosynthesis the more surface area available the more energy available, and thus life will be encouraged to focus on covering as much surface area as possible. There isn't enough of a justification to evolve complex intellect and movement, even if the energy density allowed it, for a 'plant', the optimal strategy is to go with the R approach of spreading uot with lots of plants and growing as fast as possible, and generally just enduring being eaten, rather then adopting complex locomotion that would be a prerequesite for a sapient brain to be advantageous.

Instead the only means I could see is for this species to produce their energy via a form of chemosynthesis which requires a limited chemical or substance to fuel the reaction. Such that the creature had to evolve locomation to persue this chemical it needs to fuel it's energy production. Effectively the creature still 'eats' and still 'hunts', it just happens to be hunting a non-organic substance which technically makes it autotrophic.

This substance would have to be renewable enough to sustain a species for a very long time, even from an evolutionary perspective, but also require hunting to find. This would suggest it's a substance created as a side effect of a major weather pattern or something similar. As to what that substance is...I have no idea. I'm not a chemist so I can't even begin to think of a good source of energy that would be produced regularly enough but still be consolidated into a high energy density container and spread out enough to require movement to find and collect it.

Even assuming you had that though...the species in question is unlikely to ever become sapient. It's not that such a species couldn't theoretcially become sapient, the problem is that they are too slow in the evolutionary arms race. Species that prey on this species will have a far higher energy density available to them, which will mean more available energy to spend on brain power. Predatory species will also have an additional driver in intellect due to their need to hunt more intellegent prey trying to avoid them. The net result is that the non-autotrophic species likely will be driven towards sapiens faster and it's quite likely they will achieve it first. Once that happens it's unlikely a second species will ever achieve sapience since the first species will likely domesticate or alter the living paterns of other intellegent species before they can evolve to sapients (and on a grimer, but frankly accurate, stand point it's likely the sapient species will develop technology of such a scale that they manage to so alter the world that they drie other species to extinction. The exponential rate of technological development once sapience is reached is so high that unimaginablely powerful technology is expected within a evolutionary heartbeat, it's just a matter of time before someone employs that technology foolishly).

So...yeah it still wouldn't happen. But I think the above description is the most proabably option if you wanted to create a world with an autotrophic sapient species and you would simply have to handwave the other topics.

Answer 12

Some form of competition would seem to be inevitable, as various sub elements of the machine ecosystem competed for resources. They might not "eat" each other in ways that we would understand the term, but there would be analogous behaviours including predation, parasitism and even symbiosis, and perhaps stranger behaviours which have no direct analogues in the natural environment.

Taking over CPU cycles of "prey" and running botnets to consume their computing resources could be considered a form of predation if done by force, or parasitism if delivered stealthily. There may even be mutually beneficial relationships between elements of machine ecosystems where units share CPU cycles for particular tasks in a symbiotic relationship. This is just a very simple analogy, and I'm sure far more complex arrangements could be imagined.

Answer 13

You could rig a scenario where only one species evolved and survived. If your ancestor species died out due to an environmental change you could have a singular species. This would ease pressure and allow you to stay stationary evolution wise. You would need some way to keep them stationary on autotrophism though, so they didn't branch out into another species through random mutation. Two ways I can think to do this are DNA repair on (or more likely above) the level of Deinococcus radiodurans and/or being on a local or global optima for the environment. You could still have genetic variation as long as it was for minor traits, but a smaller gene pool like in Cheetahs would be ideal.

As others have pointed out, sentience requires a high price in energy and so civilization may be a large leap even with these constraints. You would require an energy source rivaling fat and protein, as well as pressure to evolve sentience. I would imagine photosythesis would need to be better than any we currently know of, on top of having something like smart carnivores in your prehistory to drive evolution.

Answer 14

So compitition among plants is very much possible. As an on and off gardener, I have to do something about the weeds that will pull nutrients out of the soil from my desired plants. And don't get me started on my neighbors, who thought Ivy was a good idea and it's now running into my arms and agressively strangling every tree it can get it's runners on. And if a tree falls in a rainforest, and no one is around to hear it, I couldn't tell you what sound it makes, but there will be a lot of up and coming vegetation that will take advantage of an opening of sun in the otherwise dark canopy.

Answer 15

The Semiosis Duology by Sue Burke features an autotrophic civilization (or at least the remains of a past one) on the planet Pax, but not a completely autotrophic ecosystem. Pax has animals, and the animals eat plants, and they eat each other... but the pressure of competing with other plants in the presence of animals has resulting in many plants developing intelligence. This allows them to do three things: to intentionally tailor their growth patterns and toxin production to better compete with whatever specific other plants are trying to grow in their vicinity, to negotiate with other plants growing in their vicinity to share resources and improve their chances against other plants, and to actively control animals.

On Earth, there are plenty of examples of animal/plant pairs co-evolving symbiotic relationships, but new ones take evolutionary time scales to establish. The fact that plants on Pax are sapient, however, allows them to intentionally establish new animal relationships on the scales of months, rather than tens or hundred of generations, using intentional growth patterns and targeted production of psychoactive chemicals to teach and take control of animals that they find useful--and that gives them the ability to build a technological civilization, using the most convenient animal drones that are available to them in any particular place or time.