Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures

by Merlin Sheldrake

Plants only made it out of the water around 500 million years ago because of their collaboration with fungi, which served as their root systems for tens of million years until plants could evolve their own.

In 2017, researchers reconstructed the diets of Neanderthals, cousins of modern humans who went extinct approximately 50,000 years ago. They found that an individual with a dental abscess had been eating a type of fungus, a penicillin-producing mould, implying knowledge of its antibiotic properties. There are other less ancient examples, including ‘the Iceman’, an exquisitely well-preserved Neolithic corpse found in glacial ice, dating from around 5,000 years ago. On the day he died, the Iceman was carrying a pouch stuffed with wads of the tinder fungus (Fomes fomentarius) that he almost certainly used to make fire, and carefully prepared fragments of the birch polypore mushroom (Fomitopsis betulina) most probably used as a medicine.

When we use drugs produced by fungi we are often borrowing a fungal solution and rehousing it within our own bodies. Fungi are pharmaceutically prolific, and today we depend on them for many other chemicals besides penicillin: cyclosporine (an immunosuppressant drug that makes organ transplants possible), cholesterol-lowering statins, a host of powerful antiviral and anti-cancer compounds (including the multi-billion-dollar drug Taxol, originally extracted from the fungi that live within yew trees), not to mention alcohol (fermented by a yeast) and psilocybin (the active component in psychedelic mushrooms recently shown in clinical trials to be capable of lifting severe depression and anxiety).

According to these anthropocentric definitions, humans are always at the top of the intelligence rankings, followed by animals that look like us (chimpanzees, bonobos, etc.), followed again by other ‘higher’ animals, and onwards and downwards in a league table – a great chain of intelligence drawn up by the ancient Greeks, which persists one way or another to this day. Because these organisms don’t look like us or outwardly behave like us – or have brains – they have traditionally been allocated a position somewhere at the bottom of the scale. Too often they are thought of as the inert backdrop to animal life. Yet many are capable of sophisticated behaviours that prompt us to think in new ways about what it means for organisms to ‘solve problems’, ‘communicate’, ‘make decisions’, ‘learn’ and ‘remember’. As we do so, some of the vexed hierarchies that underpin modern thought start to soften.

For your community of microbes – your ‘microbiome’ – your body is a planet. Some prefer the temperate forest of your scalp, some the arid plains of your forearm, some the tropical forest of your crotch or armpit. Your gut (which if unfolded would occupy an area of 32 square metres), ears, toes, mouth, eyes, skin and every surface, passage and cavity you possess teem with bacteria and fungi. You carry around more microbes than your ‘own’ cells. There are more bacteria in your gut than stars in our galaxy.18

Male orchid bees collect scents from the world and amass them into a cocktail which they use to court females. They are perfume makers. Mating takes seconds, but gathering and blending their scents takes their entire adult lives. Although he hadn’t yet tested the hypothesis, my friend had a strong hunch that the bees were harvesting fungal compounds to add to their bouquets. Orchid bees are known to have a taste for complex aromatic chemicals, many of which are produced by fungi that break down wood.

Fungi produce plant growth hormones that manipulate roots, causing them to proliferate into masses of feathery branches – with a greater surface area, the chances of an encounter between root tips and fungal hyphae become more likely. (Many fungi produce plant and animal hormones to alter the physiology of their associates.)

One species – Arthrobotrys oligospora – behaves like a ‘normal’ decomposer in the presence of plenty of organic material and, if needs be, can produce nematode traps in its mycelium. It can also coil around the mycelium of other types of fungi, starving them, or develop specialised structures to penetrate and feed off plant roots. How it chooses between its many options remains unknown.

When trying to understand the interactions of non-human organisms, it is easy to flip between these two perspectives: that of the inanimate behaviour of pre-programmed robots on the one hand, and that of rich, lived, human experience on the other. Framed as brainless organisms, lacking the basic apparatus required to have even a simple kind of ‘experience’, fungal interactions are no more than automatic responses to a series of biochemical triggers. Yet the mycelium of truffle fungi, like that of most fungal species, actively senses and responds to its surroundings in unpredictable ways. Their hyphae are chemically irritable, responsive, excitable. It is this ability to interpret the chemical emissions of others that allows fungi to negotiate a series of complex trading relationships with trees; to knead away at stores of nutrients in the soil; to have sex; to hunt; or to fend off attackers.

Fungi may not have brains, but their many options entail decisions. Their fickle environments entail improvisation. Their trials entail errors. Whether in the homing response of hyphae within a mycelial network, the sexual attraction between two hyphae in separate mycelial networks, the vital fascination between a mycorrhizal hypha and a plant root, or the fatal attraction of a nematode to a fungal toxic droplet, fungi actively sense and interpret their worlds, even if we have no way of knowing what it is like for a hypha to sense or interpret. Perhaps it isn’t so strange to think of fungi as articulating themselves using a chemical vocabulary, arranged and rearranged in such a way that it might be interpreted by other organisms, whether nematode, tree root, truffle dog or New York restaurateur. Sometimes – as with truffles – these molecules might translate into a chemical language we can, in our way, understand. The vast majority will always pass over our heads, or under our feet.

Like plants, fungi can ‘see’ colour across the spectrum using receptors sensitive to blue light and red light – unlike plants, fungi also have opsins, the light-sensitive pigments present in the rods and cones of animal eyes. Hyphae can also sense the texture of surfaces; one study reports that young hyphae of the bean rust fungus can detect grooves half a micrometre deep in artificial surfaces, three times shallower than the gap between the laser tracks on a CD. When hyphae felt together to make mushrooms, they acquire an acute sensitivity to gravity. And as we’ve seen, fungi maintain countless channels of chemical communication with other organisms and with themselves: when they fuse or have sex, hyphae distinguish ‘self’ from ‘other’, and between different kinds of ‘other’.

Dormancy appears to be the most important survival strategy for lichens, but they have others. The hardiest lichen species have thick layers of tissue that block damaging rays. Lichens also produce more than a thousand chemicals that are not found in any other life forms, some of which act as sunscreens. A product of their innovative metabolisms, these chemicals have led lichens into all sorts of relationships with humans over the years: from medicines (antibiotics) to perfumes (oak moss), to dyes (tweeds, tartan, the pH indicator litmus), to foods – a lichen is one of the principal ingredients in the spice mix garam masala.

One of the best-studied cases is that of the fungus Ophiocordyceps unilateralis, which organises its life around carpenter ants. Once infected by the fungus, ants are stripped of their instinctive fear of heights, leave the relative safety of their nests and climb up the nearest plant – a syndrome known as ‘summit disease’. In due course the fungus forces the ant to clamp its jaws around the plant in a ‘death grip’. Mycelium grows from the ant’s feet and stitches them to the plant’s surface. The fungus then digests the ant’s body and sprouts a stalk out of its head, from which spores shower down on ants passing below. If the spores miss their targets, they produce secondary sticky spores which extend outwards on threads that act like trip wires.

Zombie fungi control the behaviour of their insect hosts with exquisite precision. Ophiocordyceps compels ants to perform the death grip in a zone with just the right temperature and humidity to allow the fungus to fruit: a height of twenty-five centimetres above the forest floor. The fungus orients ants according to the direction of the sun, and infected ants bite in synchrony, at noon. They don’t bite any old spot on the leaf’s underside. Ninety-eight per cent of the time, the ants clamp onto a major vein.

The behaviours of infected ants don’t pass without a trace. Ants’ death grips leave distinctive scars on leaf veins, and fossilised scars push the origins of this behaviour back into the Eocene epoch, 48 million years ago. It is likely that fungi have been manipulating animal minds for much of the time that there have been minds to manipulate.

Some time around 600 million years ago, green algae began to move out of shallow fresh waters and onto the land. These were the ancestors of all land plants. The evolution of plants transformed the planet and its atmosphere and was one of the pivotal transitions in the history of life – a profound breakthrough in biological possibility. Today, plants make up 80 per cent of the mass of all life on Earth and are the base of the food chains that support nearly all terrestrial organisms.1 Before plants, land was scorched and desolate. Conditions were extreme. Temperatures fluctuated wildly and landscapes were rocky and dusty. There was nothing that we would recognise as soil. Nutrients were locked up in solid rocks and minerals, and the climate was dry. This isn’t to say that land was completely devoid of life. Crusts made up of photosynthetic bacteria, extremophile algae and fungi were able to make a living in the open air. But the harsh conditions meant that life on Earth was overwhelmingly an aquatic event. Warm, shallow seas and lagoons teemed with algae and animals. Sea scorpions several metres long ranged the ocean floor. Trilobites ploughed silty seabeds using spade-like snouts. Solitary corals started to form reefs. Molluscs thrived.

These early alliances evolved into what we now call mycorrhizal relationships. Today, more than 90 per cent of all plant species depend on mycorrhizal fungi. They are the rule, not the exception: a more fundamental part of planthood than fruit, flowers, leaves, wood or even roots. Out of this intimate partnership – complete with co-operation, conflict and competition – plants and mycorrhizal fungi enact a collective flourishing that underpins our past, present and future. We are unthinkable without them, yet seldom do we think about them. The cost of our neglect has never been more apparent. It is an attitude we can’t afford to sustain.

One of the biggest limits to plant growth is a scarcity of the nutrient phosphorus. One of the things that mycorrhizal fungi do best – one of their most prominent metabolic ‘songs’ – is to mine phosphorus from the soil and transfer it to their plant partners. If plants are fertilised with phosphorus, they grow more. The more plants grow, the more they draw down carbon dioxide from the atmosphere. The more plants live, the more plants die, and the more carbon is buried in soils and sediments. The more carbon that is buried, the less there is in the atmosphere.

With their help, plants in the Devonian period were able to mine minerals like calcium and silica. Once unlocked, these minerals react with carbon dioxide, pulling it out of the atmosphere. The resulting compounds – carbonates and silicates – find their way into the oceans where they are used by marine organisms to make their shells. When the organisms die, the shells sink and pile up hundreds of metres thick on the ocean floor, which becomes an enormous burial ground for carbon. Add all of this up and climates start to change.

Most plants – from a potted snapdragon to a giant sequoia – will develop differently when grown with different communities of mycorrhizal fungus. Basil plants, for example, produce different profiles of the aromatic oils that make up their flavour when grown with different mycorrhizal strains. Some fungi have been found to make tomatoes sweeter than others; some change the essential oil profile of fennel, coriander and mint; some increase the concentration of iron and carotenoids in lettuce leaves, the antioxidant activity in artichoke heads, or the concentrations of medicinal compounds in St John’s wort and echinacea.

Between 20 and 40 per cent of crops are lost each year to pests and diseases, despite colossal applications of pesticide. Global agricultural yields have plateaued, despite a 700-fold increase in fertiliser use over the second half of the twentieth century. Worldwide, thirty football fields’ worth of topsoil are lost to erosion every minute. Yet a third of food is wasted, and demand for crops will double by 2050. It is difficult to overstate the urgency of the crisis.

When broad bean plants are attacked by aphids, for example, they release plumes of volatile compounds that drift out from the wound and attract parasitic wasps that prey on the aphids. These ‘infochemicals’ – so-called because they convey information about a plant’s condition – are one of the ways plants communicate, both between different parts of their own bodies, and with other organisms.