Photo: biodiversity heritage library/public domain

The magic of mushrooms forces us to rethink what intelligence means

The astonishing secrets of fungal life raise profound questions
October 7, 2020

One of biology’s enduring struggles since Darwin’s time has been to throw off the hierarchy in which all living things are judged by their proximity to the supposed pinnacle of evolution: humans. If we measure evolutionary success in terms of sheer biomass, bacteria outweigh all animals on Earth by a factor of about 35, while the humble fungi exceed the world’s fauna by around sixfold. Evolution, as the biologist Stephen Jay Gould unflaggingly tried to explain, has no overarching goal: it is not trying to make organisms that are more complex or smarter. It is merely the process by which every lineage of organisms adapts to thrive in its own niche—and evidently, simplicity is often the best solution.

Yet the biological sciences themselves are still trapped in human-centred thinking. There is a pecking order in which the study of humans—even if at the reductionistic level of genes and cells—has primacy, with mice and fruit flies close behind as convenient proxies for trying to unravel our own biology. At the other end of the complexity scale, bacteria are well studied, in part because they are so ubiquitous and important to our own wellbeing, but also because their simplicity and the ease with which they can be grown in the lab makes them useful for understanding the basic processes of human (and other forms of) life: how genes are replicated, how enzymes work.

Plant biology, meanwhile, though important for agriculture, remains underappreciated. But even plants enjoy greater status than fungi, the third of the multicellular branches (along with animals and plants) on the “eukaryotic” limb of the tree of life (that is, those organisms with complex cells that partition their genes in nuclei). Part of mycologist Merlin Sheldrake’s purpose in Entangled Life is to stick up for mushrooms—and indeed to explain why there is much more to fungi than mushrooms alone. Mycology, the study of fungi, is a “neglected megascience,” in the words of one of its practitioners—yet you don’t have to delve very deep into it to be intrigued. Consider the “zombie fungus” Ophiocordyceps unilateralis, which infects a species of ant and in effect takes over the insect’s brain. An infected ant is compelled to lose its instinctive aversion to heights, clamber up a plant, and lock its jaws into the plant tissue. What follows sounds like a nightmare out of science fiction. The fungus stitches the ant’s feet to the plant surface, grows through and digests the body, and sprouts mushroom-like from the head to spread its spores.

This might look like the Darwinian struggle for survival at its most ruthless. Yet Sheldrake’s deeper goal here is to suggest that the neglect of fungi in biology has skewed our view of life inordinately towards that picture of “red in tooth and claw” competition. It’s not wrong exactly, but incomplete. Fungi show us what an astonishing variety of ways there are to exist within the constraints of Darwinian evolution, in particular by developing intimate and yet promiscuous symbiotic relationships with other organisms: they help one another, but not exclusively. As a love letter to this undervalued form of life, Sheldrake’s book is deeply engaging and constantly surprising. But its ultimate message goes further, showing that the story of life on Earth can be given many narratives.

Take lichens, such as the pale green stuff you often see on tree bark or rocks. These organisms are symbiotic combinations of algae and fungi (and are also packed with bacteria), and they exist all over the planet, covering as much as 8 per cent of its surface—more than tropical rainforests. They are perhaps the hardiest organisms known, able to survive on spacecraft bathed in ionising cosmic rays. We don’t even really know how to think about such composite lifeforms: they are like micro-ecosystems that “confuse our concept of identity and force us to question where one organism stops and another begins,” Sheldrake says. In fact, it might be better to think of lichens not as combinations of autonomous component parts but as “stabilised networks of relationships”: the components are the notes, but the organism is the song.

Or take mycelium: “ecological connective tissue, the living seam by which much of the world is stitched into relation.” It consists of fine fungal strands called hyphae that lace through soil like blood vessels through flesh—and also “along coral reefs, through plant and animal bodies both alive and dead, in rubbish dumps, carpets, floorboards, old books in libraries, specks of house dust and in canvases of old master paintings.” In a teaspoon of soil, there might be 10km of hyphae; mushrooms are (literally) their fruit.

“Mycelium is a way of life that challenges our animal imaginations,” Sheldrake writes. Some hyphae are sensitive to light, wind, temperature, moisture, surface texture and electrical fields, and can detect and navigate around nearby objects. Some networks stretch over kilometres and can be thousands of years old (whatever that can mean, exactly, for such a “distributed” organism). The Nobel laureate biologist Max Delbrück considered mycelium “the most intelligent” of simple multicellular organisms.

Fungi force us to reconsider what intelligence even means. It’s an emotive, slippery and in many ways unhelpful word—for many people it is synonymous with sentience or consciousness, while at the same time being notoriously hard to measure even within a given species, let alone to compare across the species divide. Many animal behaviourists prefer instead to speak of cognition: the neural processes that govern behaviour. But that generally assumes a brain, or at least a nervous system. Plants and fungi have neither.

What they do share in common with us and other “higher” animals is a system of branching filaments that act as conduits for signals of some kind—signals that put cells and tissues here in touch with those there. Mycelial networks may send electrical pulses along their hyphal strands, reminiscent of those that travel through nerves. Some mycologists have suggested that these filamentary fungal webs, like the entangled root systems of forests, can be regarded as analogues of the dense neural networks inside our skulls, so that both plants and fungi display a kind of cognition, even intelligence. Others regard that as absurd talk: these networks might be more akin to those of river basins, distributing matter and energy without any cognitive process.

The whole argument rather misses the point. Attributing sentience to fungal networks might indeed be a wild leap—but then perhaps sentience, including our own, is just a poorly-understood byproduct of the primary goal of systems like our neural structures, namely to convey and process sensory information from the environment in ways useful to survival and growth. And with fungal networks, this processing isn’t just a passive affair in the manner of roads acting as conduits for traffic. Fungal networks possess a capacity for solving novel problems, such as growing through a maze to locate the shortest path to the exit. Some researchers are exploring their electrical signalling to make what they call living fungal computers—not to perform calculations, but perhaps to act as environmental sensors that can report soil quality or pollution.

[su_pullquote]“Mushrooms are not just mind-expanding; they expand the very concept of mind”[/su_pullquote]

Whether this qualifies as intelligence is a matter of semantics. It’s more useful to recognise that what has previously been considered intelligence, often with an anthropocentric bias, is now increasingly being subsumed into a broader question: how do biological entities acquire, represent and integrate information and come to possess memory, predictive ability, agency and self-identity? Our own mental processes and the “reasoning” of fungi are two different but related answers to these general questions. The magic of mushrooms is not merely mind-expanding, then; it might expand the very concept of mind.

Symbiotic relationships of fungi and plants are in fact the norm: more than 90 per cent of all plant species rely for their viability on fungi called mycorrhizae to sequester nutrients from the soil, while returning the favour by allowing the fungi to enjoy the benefits of photosynthesis, the harvesting of energy from sunlight for metabolism and growth. Mycorrhizal filaments may also carry vital molecules from one plant to another, blurring their status as separate organisms; other micro-organisms such as bacteria ride this organic subway too. And as with lichens, it makes no sense to ask here who dominates the relationship, who is “farming” whom.

Plants and fungi can find new partners in different environments, and are altered as a result: certain mycorrhizae make strawberries sweeter, change the taste of herbs and tomatoes or the baking properties of wheat flour.

Photosynthesis is often seen as a sine qua non of plant life: it requires the light-harvesting chlorophyll pigments that make plants green, and drives the production of the organic material they need for their growth and survival. But in at least one case, mycorrhizal fungi have produced a plant species—the ghost plant (Monotropa uniflora), native to the American northwest and Asia—that doesn’t use photosynthesis at all.

Monotropa lacks chlorophyll entirely, and is deathly white, indeed looking rather fungal, like “clay tobacco pipes balanced on their ends.” The plants depend on the carbon compounds supplied, via fungal conduits, by other plants—and, oddly, they don’t appear to reciprocate any favours. But this is only an extreme example of a common trait; all orchids, for example, lean on fungal networks for their nutrition at some stage in their development.

Sure, we could choose to see this as a case of one organism “exploiting” others to survive—that’s the classic neo-Darwinist view. But it’s an arbitrary narrative. We could alternatively fabricate a cosy, romantic story about cooperation to counter the brutal one offered by survival of the fittest—but “cooperation” is no less anthropomorphic than “selfishness.” Mycorrhizae are simply showing life for what it really is: connection. Biology needs new ways to describe and reckon with the interconnectedness of all life—for no organism, not even fungus, is an island. Mycology can help. But the question, Sheldrake says, is whether we can talk about what he calls these “wood wide webs” without “leaning on one of our well-worn human totems.”

Sheldrake is not immune to romanticism of his own. His account of the mind-altering properties of magic mushrooms has a touch of the shaman about it: all very well, but descriptions of other people’s hallucinogenic trips tend to be tiresome. (The son of maverick biologist Rupert Sheldrake, Merlin grew up among colourful company, and the apple clearly didn’t fall far from the tree.) He breezily describes the potential of fungal hallucinogens such as psilocybin to treat disorders like depression, downplaying the possible dangers and the mixed and still rudimentary evidence of their efficacy. And in entertaining the speculations of his father’s friend, the “eccentric author, philosopher and ethnobotanist” Terence McKenna that, by altering our consciousness, psilocybin mushrooms are somehow “wearing our minds” much as “zombie fungi” do for ants, he risks stepping into the Age of Aquarius.

But these are quibbles about what is otherwise a balanced, well-informed and at times beautifully written book. Sheldrake ends with a paean to “radical mycology,” a mostly “citizen science” movement that aims to redress the professional neglect—the equivalent of the amateur astronomers who regularly contribute real advances to their field. Some of these folks just like growing edible mushrooms; some, inevitably, are drawn to the hallucinogens. Others study the potential of fungi to sequester pollutants such as heavy metals; one collaborates with scientists to look for antiviral agents in fungi. (Let’s not forget that the first antibiotic, penicillin, came from a fungal mould.) Radical mycology organises itself like its subject matter, with “decentralised mycelial logics.”

Sheldrake is a spirit in tune with this anarchic approach. He gets drunk on cider fermented from apples scrumped at night from a cutting from Isaac Newton’s famous apple tree. And he announces in the epilogue that he will grow and eat oyster mushrooms from a dampened copy of his book. But beneath the playfulness is a serious and disruptive question: how different would our societies look, Sheldrake asks, if we thought of fungi rather than animals and plants as “typical” life forms?

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Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures, by Merlin Sheldrake (Bodley Head, £20)