This is for a novel I'm writing. The basic premise is that massive networks of mycelium running under the soil combine to form a decentralised intelligence that has been managing life and conditions on the planet for hundreds of millions of years. Think Gaia theory, but way weirder. Humans occasionally making contact with the mycelial intelligence explains much religious and supernatural experience in my world.

The big conflict/mystery of my novel is that the mycellium have decided humanity have outlived their usefulness and engineer a population cull. But what I need to explore further is: how if at all might what in essence amounts to entire ecosystems acting with self awareness impact humanity?

Edited to add: Thank you for all the responses. Its given me a lot of food for thought.

My thinking is the mycelia is "magically" intelligent as a result of its current biology. We already know that mycelia will link up, share resources and communicate, so its not too much of a stretch.

MY thinking is that the mycelia doesn't have much ability beyond what actual mycelia has. They mostly manage the ecosystem by nurturing certain plants, or feeding them particular chemicals in order to achieve specific changes.

In terms of knowledge and psychology, i'd see them as having extensive ecological knowledge, but a very poor understanding of anything that happens at human timescale - not none, but little. We're talking immensely long-lived intelligence. They're quite happy to invest a few decades into a plan, since thats a trivial length of time for them.

As for methods, I see them going for something subtle and targetted. They don't need to wipe out humanity completely - a 90% population drop would be more than sufficient. And I imagine their preferred method would be to have us do it to ourselves somehow, preferably in a way that would keep collateral damage to other species or wider ecosystems to a minimum. My thinking is drugs that undermine critical thinking, and promote the kind of psychology that would breed violent ideologies or something like that.

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    $\begingroup$ You mean like in that movie with the big blue guys? What's its name? Ah, Avatar. $\endgroup$ – Ghanima Nov 7 '15 at 10:00
  • $\begingroup$ What level of "managing life and conditions on the planet" is it capable of? Or is that what you're asking us to figure out? $\endgroup$ – Samuel Nov 9 '15 at 18:15

Self awareness or the Hard Problem of Consciousness has been extensively debated by scientists, psychologists and philosophers. So what I (or anyone else, for that matter) can provide here is not a definite answer, but only an opinion based on common knowledge and some assumptions.

Self awareness is a property somewhat different from intelligence. A mycelium may be self-aware right now, for all we know. Some religions believe that this indeed is the case and every creature possesses a soul that makes them self aware. From a scientific point of view, we do not know if other organisms are self-aware like we are, but it is often assumed since we evolved from them. Of course, for this to be said, we have to make the assumption the we ourselves are self aware.

Intelligence, on the other hand, is something that can be quantified. We have a pretty good idea as to which creature has how much intelligence based on their behaviour, as well as studying their nervous systems.

Returning to your question... If you have said that mycelia are capable of fighting against humanity, you've granted them intelligence and power. Self-awareness, probably similar to humans is also required, but that is only a small condition. Now that they are an intelligent species , we can raise the usual questions:

  1. How intelligent are they? Equal to humans, way ahead of us, or slightly ahead?
  2. Do they have the same physical form as actual mycelia or is it different?
    (a) Do they have an intricately developed nervous system like a human? Is it microscopic? Or are you granting them intelligence by magic, without altering their physical form?
    (b) How much physical strength do they have? For example, even if they knew how to create a nuclear weapon, they may not have the physical strength to actually build one.
  3. What knowledge have they acquired so far? It is likely that a species with similar intelligence and different physical form from humans (not to mention a different environment and differently abled physical senses of the organisms themselves) will have evolved a different social system and culture, as well as different levels of knowledge in different scientific fields.
  4. What inherent psychological rules are they genetically designed to follow? For example, humans tend to perform activities for personal luxury. They desire fame, power and love in varying amounts. They naturally detest pain. They have instincts that cause them to be nervous in specific scenarios and frightened in others. Is any of this true for the species?

Have you seen that one movie with Mark Wahlberg, "The Happening", where plants mutate to produce "spores" which make people go crazy and commit suicide?

If a plant based intelligence - who's been running the world behind the scenes - suddenly decided to cull mankind they might be able to do something similar (but maybe more realistic).

Subtlety genetically modify our crops in a way that was lethal to us, but not necessarily to animals, for example (imagine mycelium slowly weaving itself into the plants in major cities, and releasing a toxin at a carefully timed/planned moment). Or making grass give off a hallucinogenic substance which causes people to become incredibly violent, and lose their ability to reason - think "28 days later".

At that point you have a lot of leeway as to how this intelligence would deal with mankind. Whether the mycelium intelligence would deal with humans "personally", or just set the stage for World War 3, and thus for humanity to wipe itself out.

The problem as I see it is that I don't know how humans would be able to defend themselves, or defeat this intelligence that they don't even know exists.


To answer your question, you need to look at what the ecosystem is willing to do to get rid of humans. Just because a conscious entity believes something has outlived its usefulness does not mean it automatically engages in total warfare to get rid of it. I'm sure we don't think mosquito have any usefulness, but they still exist!

An ecosystem that is conscious will be well aware that everything it does hangs in a balance. It may be able to get rid of the humans, but it must live with whatever it does to get rid of us!

So how badly does the biome want us gone? Are they willing to sacrifice all land-dwelling life to get rid of us? How about just forest life? Are they willing to make it harder for deer everywhere to reproduce for the rest of time? These kinds of questions will answer what they actually do.

As for what they can do? By your description, they have been like a gardener maintaining a garden of prized rose bushes. Think about how much damage a gardener could do to their garden by simply not helping.


Dexyan mentioned Cordyceps, an unusual type of fungus that hijacks its host's nervous system to spread and eventually makes its host position itself (just before it dies mind you) in just the right place to disperse its spores. For ants, Cordyceps has its dying host climb up a plant and bite down on the underside of a leaf, right over a well-used ant trail, so its spores will infect any ants passing by below.

You said the mycelia believe humans outlived their usefulness, yes? You didn't specify, so I am left to conclude one of the two choices:

  1. humans have become a detriment (threat) to the mycelia instead of a benefit,
  2. humans have become aware of the fungi's meddling and/or has become awfully willful, and the mycelia will not allow humans to leave its control. Think Britain during the American Revolution, or if you want an example more like what I'm thinking, the Othermind of the Breath-of-Evil plant in the Wings of Fire series. Seriously, it's a self-aware and sapient, possessive, and power-hungry plant. I'd highly recommend researching it, though you'll likely have to go on a fandom.wikia site to do so.

While the mycelia is relatively limited in its options (poisonous and/or infectious spores can only do so much against an intelligent, adaptive species such as ourselves, which will likely realize what's going on, don gas masks and hazmat suits, and try its darndest to exterminate the mycelia) it will likely see the potential in hijacking humanity and effectively taking their intelligence and resources for themselves.

Why? Because they have extensive ecological knowledge; humans have and are continuing to cause mass extinctions, and the mycelia has had an awful lot of time to realize our sheer destructive potential. Destroying a fungus is one thing; destroying an army of intelligent humans is quite another. Mycelia are connected despite the distance between continents, so they likely know of Hiroshima and will realize the need to take care of the nuclear threat.

Ergo, they will hijack small creatures that are relatively common (and stealthy) to spy on and find out whoever has the code to the nukes. Ants, roaches, pigeons, and rats would be essential. Then, after locating their targets, the mycelia will strategically sprout a fruiting body and spam spores on the unfortunate humans.

"But why not hijack the animals and have them deal with the humans?" Humans are the greatest exterminators on the planet, we're great survivors due to intelligence and adaptiveness, and some of us would likely pull off survival despite an all-out assault from the animal kingdom. Sure, it'd be difficult to make shelters against everything, but if we can create nukes and send a man to the moon, we can surely survive such an attack.

At this point, the mycelia, which communicates with each other, will realize the untapped potential of the human mind (and genetic engineering). It will realize humanity is still useful; to act as think tanks and manpower, as well as bring it to the best possible genetic state.


Vegitarians and Animal rights activists would protest against antibiotics. It could be a devicive issue like "abortion."


mycelia allready are somewhat intelligent, as they give moreor less nutrients to plants depending on how they are and what are their needs, if you just make it so it is more powerfull individually, plus their hivemind capacity which can do many things said over in other answers, plus something like zombie fungi, which already exists and affects insects, makeing them do their bidding, then you have an all-out apocalypse as a lot of this planet is covered in mycelium networks, if you make your civilization live in a forest planet, then even more is, they also are quite difficult to eliminate, if you take a chunk of earth, there is more underneath, very deep there is still mycelia, which quickly regenerates, and if you try to poison it, it cuts of the poisond parts, and the chunk with mycelium still tries to grow, if it can, it will be able to spread spores, to infect more of the cities with mycelia, sorry for the disorder, any mistakes are because of my spanish keyboard bye, hope this was helpfull


Frame challenge

They live under the soil, and even if they poke fruiting bodies into the air, these don't have eyes or ears.

They don't have the power of movement in the animal sense. Their thought processes are so slow that movement of even a snail is fast beyond their understanding.

In other words they cannot have any comprehension of the animal world at all, let alone the difference between a horse and a human. The best they can do is direct the roots of trees etc. in the direction they desire. Just possibly they could have some vague awareness of earthworms as incredibly fast creatures that move through the soil leaving tunnels.


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