People are often wary of mushrooms, associating them with magic and superstition. According to German folklore, witches dance in "fairy rings" made from mushrooms, while a French fable warns that anyone who enters these circles will be cursed by huge frogs with bulging eyes. Maybe it's their appearance, or maybe it's their poisonous and psychoactive properties, but mushrooms are known to make an impression.
While we may end up on rough ground claiming mushrooms are conscious, recent experiments show that this may be true. For example, they can make individual decisions and quickly learn new information or skills. Results that highlight the spectacular sensitivity of these "simple" organisms and place a counterpart of the human mind within a spectrum of consciousness that could encompass the entire natural world.
Before we explore the evidence and clues of fungal intelligence, let's consider the definitions for a moment.
What is consciousness?
Let's get off to a good start. Whatever it is, the definition of consciousness implies the awareness, the proof of which can be expressed in reactivity or in the sensibility of an organism to the environment surrounding. Until recently, most philosophers and scientists attributed consciousness to big-brained animals and excluded other life forms. The problem, how stressed the cognitive psychologist Arthur Reberoutside, is that it is impossible to identify a threshold level of awareness or reactivity that would separate conscious animals from unconscious ones.
We can escape this dilemma, however, if we allow ourselves to identify different versions of consciousness across a continuum of species, from apes to amoebas. This does not mean that all organisms possess a rich emotional life and are capable of thinking, although mushrooms appear to express the biological rudiments of these faculties.
What are the mushrooms?
This question doesn't have a simple answer either. THE mushrooms are the reproductive organs produced by organisms that spend most of their life underground in the form of microscopic filaments called ife. These hyphae, in turn, branch out to form called colonies mycelia. The mycelia expand in three dimensions within the soil, absorbing water and feeding on roots, wood and the bodies of dead insects and other animals. Each of the hyphae in a mycelium is a tube filled with pressurized fluid and extends to its tip. The materials that feed this stretch are piped into small packages called vesicles, whose movement is guided along an internal system of "rails" by proteins that function as motors.
Hyphae can grow around obstacles and even implement a repair system if they are damaged. These actions tap into an array of protein sensors and signaling pathways that connect external physical or chemical inputs to the cellular response. The cell's electrical activity is also sensitive to changes in the environment. Voltage fluctuations across the hyphal membrane have been likened to nerve impulses in animals, but their function in fungi is poorly understood. Hyphae also react to confinement, altering their growth rate, becoming narrower and branching less frequently. The fungus, in other words, adapts to the structure of the soil and the anatomy of plant and animal tissues as they advance and forage for food.
Are mushrooms conscious? They are intelligent?
We tend to associate conscience and intelligence with the appearance of stubbornness or intentionality, that is, the decision-making process that results in a particular behavior. Whether or not humans have free will, they take actions that seem intentional: there are those who finish their coffee, and there are those who leave it halfway (just to give an example).
Fungi always express simpler versions of individualistic behavior. Branch formation patterns are a good example: each young mushroom colony takes on a unique shape, as the precise timing and emergence locations of the branches from each hypha vary. This variation is not due to genetic differences, since identical clones from a single fungus parent still create colonies with unique shapes. So what is it due to?
Mushrooms also show evidence of learning and memory. Working with fungi isolated from grassland soil, German mycologists have measured the effect of temperature changes on mycelium growth. When it heated rapidly for a few hours, the mycelium stopped growing. When the temperature dropped again, the mycelium recovered to form a series of smaller colonies from different points across the original mycelium.
Meanwhile, a different group of mycelia was exposed to mild thermal stress prior to the application of a more severe thermal shock. Colonies that had been "primed" in this way resumed normal growth very quickly after the severe stress, and continued their regular expansion rather than bouncing back here and there in the form of smaller colonies. This finding suggests that the mushrooms developed some defense mechanisms that allowed them to fend off the most severe stress. Not only that: the mushrooms retained this biochemical memory for up to 24 hours after the mild heat shock, but they forgot it soon after and succumbed to further heat stress as if they had learned nothing.
The fantastic story of a special yeast
Even the single-celled fungus present as yeast, the saccharomyces cerevisiae also used as a dry yeast by a well-known Italian mill, ha shown cellular memory capacity. Yeasts triggered by salt exposure become better at responding to other types of chemical stress. Other fungi, such as the decomposers that rot wood, exhibit this information transfer. When? As they fan out in search of dead and damaged trees, fallen branches and other food sources. When part of the mycelium finds woody debris, the extracted nutrients are distributed throughout the colony, which concentrates its growth from barren to fertile places on the forest floor. The mycelium operates as more than a mere sum of its individual hyphae; it is like an integrated multicellular organism.
Mushrooms never cease to amaze
When the researchers followed the nutrient transfer to the lab, further discoveries they started to emerge. In an earthen tray, hyphae have been observed to come into contact with a block of beech. They grow on its surface and penetrate the solid structure, secreting enzymes that destroy the polymers in the wood and release sugars that fuel their metabolism. When the mushrooms run out of energy in the block of wood, they grow in all directions, once again in search of food. This is where mushroom awareness becomes clear. When a mycelium spotted a second block of beech and was then placed in a new tray, it remembered that growing from a particular side of the block of wood had previously led to a food reward, and then tried to repeat the action.
These are tests of memory and intelligence.
Other simple forms of learning and memory have been studied in slime molds for many years. Slime molds are not fungi, but relatives of a "superstar" of biology, the amoeba. They form called sparkling yellow colonies plasmodia which ooze onto decaying wood and eat up bacteria. If there is enough moisture, these sticky "monsters" can cover the entire stump of a tree.
In a experiment of the 2010, when its plasmodium was surrounded by oatmeal arranged in the same pattern as the cities surrounding the Japanese capital, a mold created a pattern strikingly similar to the layout of the rail system around Tokyo. Responding to the need to create the shortest connections between its food stations, the slime mold has reached the same conclusions as the human architects.
Mushrooms establish relationships
The complexity behavioral fungi increases when they interact with living trees and shrubs rather than dead wood. Some of these relationships are destructive while others are mutually supportive. Pathogenic fungi can be very cunning in the way they feed on plants and escape their defenses. Mycorrhizal fungi are more cooperative, penetrating tree roots and establishing close physical connections through which water and dissolved minerals pass to trees, in exchange for the food produced by photosynthesis.
This complex symbiosis is based on a continuous chemical communication between the fungi and the plant. A relationship that affects the development of both partners.
Are forests super organisms connected "in a network" by mushrooms?
Mycorrhizae support the productivity of the entire ecosystem, stimulating some mushroom enthusiasts to reimagine forests as superorganisms connected through a "woody web" of mushrooms.
This is an intriguing idea, but the comparison with the internet may not be perfect. For starters, it does the mushrooms themselves wrong: unlike the internet, mushrooms generate their own information through active interactions with their plant partners. Second, the computer metaphor is often adopted by those who attribute almost supernatural properties to mushrooms, which is why fungal behavior has often (wrongly) been relegated to the margins of 'real' science.
Fungal expressions of consciousness are certainly very simple. But they align with an emerging consensus that, while the human mind may be particular in its refinements, it is typical in its cellular mechanisms. Fungal consciousness experiments are exciting to mycologists because they have given way to the study of behavior within the broader field of fungal biology research.
Those who study animal behavior do so without referring to the molecular interactions of their muscles; likewise, mycologists can learn a lot about mushrooms simply by paying more attention to what they do.