Researching a lot about fantasy, I've always had interest of mushroom humanoids, but I wanted to put my own twist on them. Instead of sentient mushrooms, I wanted to have a humanoid species infected with some kind of Mycorrhiza, which is a symbiotic association between a fungus and the roots of a vascular host plant.

Cases with parasitic fungi tend to not go well, but Mycorrhiza is more symbiotic, and I want to know how and why would there be a human species that has a symbiotic relationship with "parasitic" fungi? And if possible, what kind of physical differences would it have from a regular human?

  • 2
    $\begingroup$ How closely are you trying to stay to what Mycorrhiza is actually capable of? Are you just using this as an example of a symbiotic fungus, or do you actually want to know what a human/mycorrhiza symbiosis would look like? The answer to your question is extremely different depending. $\endgroup$ Aug 19, 2018 at 4:22
  • $\begingroup$ @MorrisTheCat I'm trying to ask for both, although I'm wondering if I worded it weirdly. $\endgroup$
    – TGCF
    Aug 19, 2018 at 13:08

5 Answers 5


More than half your body is not human

We all think of ourselves as everything involved in the weird meat sacks we lug around, but in reality there's a huge amount of bacteria that is absolutely integral to our wellbeing.

In fact, we're increasingly learning that this isn't even a relationship in which we own the bacteria, but rather a conversation and relationship that works both ways.

Although for us it was microscopic bacteria, I think that's a really interesting source of real world inspiration to build a species that has evolved to have this relationship with fungi.

To give an example usage, a symbiotic relationship with the penicillin fungus would give us built in access to antibiotics. Although it is unlikely to impact the appearance of a human in any significant way in this case.

  • 5
    $\begingroup$ More than half of the cells in your body are not human. They (the bacteria) just happen to be really tiny cells. Thus, 90% of your body is, in fact, human. $\endgroup$
    – RonJohn
    Aug 19, 2018 at 22:57

I'm going to go a bit off-script here and come at this from a different angle.

The short answer to your question is that a symbiotic fungus could do ALL KINDS of beneficial chemical things. Help with digesting difficult foods, providing beneficial neurotransmitters, pretty much anything that modern medicine can do with medication is potentially feasible.


If you've got this beneficial fungus, and it's going to be an element in world worth talking about, the question you should be asking yourself is what Bad Things do you want to have happen and/or what challenges do you want your characters to have to overcome when that beneficial fungus gets messed with somehow.

As it happens, the webcomic Schlock Mercenary did this exact thing last year. One of the races has a symbiotic fungus that grows like a mohawk on their heads that works like a really groovy antidepressant. At one point one of the characters gets stripped of his fungus and it makes him emotionally unstable because the sudden absence of the symbiote messes with his neurochemistry.

This is just an example, but it's useful in this context to start from the consequences and/or dramatic points you want to create and work your way backwards.

  • 1
    $\begingroup$ Indeed. For a more concrete example, a fungus that more rapidly "deals with" fatigue poisons would be interesting. Imagine being able to exercise harder, longer, without getting tired... never being sore the next morning... Or, what about a fungus that stops you from having hangovers? $\endgroup$
    – Matthew
    Nov 14, 2019 at 21:23

They could act as a separate breathing system.

Mychorizzia is a very effective nitrogen fixer. Maybe this fungi is very good at pulling O2 out of the air, separating it from toxic gasses that often occur in pockets underground.

It could even make you mushroom men be able to breath underwater, because it could (with a bit of handwavium) pull O2 from water, acting as a pseudo gill.

And in return for the O2 this fungi puts into your blood, it takes minerals and sugars.


You might want to first ask yourself where the fungus would be hosted. Each of your organs offer very different environments in which a micro-organism can live. The additional functions granted by the fungus would then depend on which organs are affected:

  • Skin: By forming a thick coating on the host's skin, the fungus would serve as a protection against physical dangers (thorns, stings, impacts) and chemical / microbiological dangers.

  • Lungs: Many fungi secrete antibiotics to fight off bacteria, so it would be interesting to have them protect the delicate interface that is your lungs from infections (if oxygen can get into your blood easily, so can bacteria).

  • Brain / Nervous system: As has been mentioned, by secrete certain neurotransmitters, the fungi could help stabilise our emotional state. They could also help protect sensitive areas, like as I mentioned for the skin.

  • Stomach / Gut: As with a lot of microorganisms that live inside us, the fungi could help us digest our food, by breaking down large molecules that we trouble digesting on your own.

For most other organs (liver, kidneys etc) you could imagine the fungi enhance their basic functions beyond normal human capabilities. It might be harder to explain how the fungus arrived there though.


You can take the example of “Parasitic Water Shrooms” from a manga called “Made in Abyss”. In the manga, the fungi attached to the host and sucks nutrients from them just like any other parasite. However, if the fungi notices that the host is about to die, it actively gives back nutrients to the host in order to keep them alive. You can make it so that the mushroom does not have such an impact on the health of the human so that the mushroom is actually more helpful than it is harmful thus causing a symbiotic relationship.

  • 1
    $\begingroup$ Note that parasites are not symbiote. $\endgroup$
    – RonJohn
    Aug 19, 2018 at 17:48
  • $\begingroup$ While its name says its parasitic, if the nutrients it sucked off were to be negligible, it would be more symbiotic than it is parasitic is what I was trying to point out. $\endgroup$
    – BlueFire
    Aug 19, 2018 at 22:27
  • $\begingroup$ Symbiotes work (though maybe unknowingly) together for the benefit of both. I don't see how "Oops, almost killed him" is for the benefit of the host. $\endgroup$
    – RonJohn
    Aug 19, 2018 at 22:56
  • $\begingroup$ @RonJohn I think they give back nutrients if the person is going to die for a third party reason. The fungus works like an extra battery cell, absorbing nutrients when there are extra and then releasing them in times when the host has a deficiency or needs a supplement. $\endgroup$ Aug 19, 2018 at 23:33
  • $\begingroup$ @ClayDeitas a truly useful symbiote would during the nutrients back when it's actually useful: being chased by a lion, chasing a gazelle, during a famine and you're nursing a child, etc. $\endgroup$
    – RonJohn
    Aug 19, 2018 at 23:37

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .