Merlin Sheldrake, 32, earned his Ph.D. in tropical ecology at the University of Cambridge for his research into underground fungal networks in the tropical forests of Panama. Since then, he has not lost his fascination for them. He is the author of "Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures," which was published in early September.
DER SPIEGEL: Dr. Sheldrake, we are here in London's Hampstead Heath. This place, you write in your book, means more to you than any other. Why is that?
Sheldrake: I grew up here. This is where I learned to walk. Later, I climbed trees here, and still later, I had parties with friends. And my interest in nature has been incubated by this place.
DER SPIEGEL: Your interest in nature in general, or fungi in particular?
Sheldrake: Both. I've always been particularly interested in how things transform, how they grow and decompose. I was amazed how piles of leaves disappear over time. How did this transformation come about without me being able to see anything? Composting, I understood, is largely the work of fungi.
DER SPIEGEL: For most people, nature is primarily made up of plants and animals. What role do fungi play in between those two realms?
Sheldrake: Fungi are of enormous importance. The basic principle of ecology is the relationships between organisms - and fungi form connections between organisms and so embody this idea.
DER SPIEGEL: If fungi are so important, why don’t we see them all over the place?
Sheldrake: Oh, fungi are everywhere. Just take this leaf: Between tens and hundreds of species of fungi live on and in it. No plant has ever been found in nature which does not have fungi in its leaves and in its shoots. Or take the roots of the grass we are walking on, the rotting twigs, the soil under our feet: There are fungi everywhere. You have yeast all over your body, in the lining of your ears, in your nostrils. Even in the air: At this moment, you are breathing fungi. Fifty million tons of fungal spores are floating in the atmosphere, the largest source of living particles in the air. And they change the weather by causing water droplets to form.
DER SPIEGEL: If fungi are so ubiquitous, why we know so little about them?
Sheldrake: There are many reasons. The most obvious one is access. The fungus we see is nothing more than the fruit of the organism itself. The mycelium network that belongs to it is buried in the ground. It is as if we only saw acorns for one moment every year, but we couldn't see the magnificent oak trees.
DER SPIEGEL: Do even scientists underestimate the importance of fungi?
Sheldrake: They did so for a long time, at least. Until the 1960s, fungi were thought to be plants. Only then did they gain taxonomical independence. The new sequencing techniques have changed that. Today, we can read the DNA in every teaspoon of soil and find out who is there.
The article you are reading originally appeared in German in issue 39/2020 (September 19, 2020) of DER SPIEGEL.
DER SPIEGEL: And? What does one find?
Sheldrake: The kingdom of fungi is vast. There are six times more species of fungi than of plants, and only 6 to 8 percent of them have even been described. We still know so little! ! Just one thing is clear: There are many ways to be a fungus.
DER SPIEGEL: Is perhaps the lack of appreciation for fungi because of the fact that they are not very nutritious and often even poisonous?
Sheldrake: Many people think like that. But in fact, many mushrooms contain important minerals and they have a high content of antioxidants. They produce an amazing variety of substances that affect cancer, viruses or our immune system. And mushrooms are high in protein. Truffles are a good example of an edible fungus. After all, they want to be eaten. Truffles sit deep in the ground where no wind can spread their spores. They attract animals with a very subtle mixture of odors, so that these animals then eat them and spread their spores.
DER SPIEGEL: Some mushrooms lure us with substances that have a direct effect on our consciousness ...
Sheldrake: Yes, about 200 fungal species contain psilocybin, a substance that people have been interested in because of its strong psychedelic effects.
DER SPIEGEL: Such mushrooms cause hallucination and change the way we think. How do mushrooms benefit from making psychedelic drugs for humans?
Sheldrake: We don’t know. The first mushrooms to make psilocybin lived 75 million years ago, long before humans arose. But the receptors that this substance binds to can also be found in many animals. Does psilocybin change the behavior of certain insects in a way that induces them to spread fungal spores? Or do they change the behavior of insects in a way that deters them from eating the mushrooms?
DER SPIEGEL: Have you personally tried the effects of psychedelic mushrooms?
Sheldrake: Yes, under their influence I realized that most of my consciousness was unknown to me. It was as if I had spent my life in a garden until then, and now I suddenly discovered that this garden has a gate through which I can enter a strange and wonderful forest, that was largely unknown to me.
DER SPIEGEL: Does the gate disappear once the effects of psilocybin fade away?
Sheldrake: Not necessarily. Once you know that this forest exists, it is much easier to find your way into it.
DER SPIEGEL: You even took part in a scientific study.
Sheldrake: Yes, though it was LSD tested in that study. But both substances have similar effects. Among other things, it was to be examined whether LSD promotes creativity. Each participant had to name a problem they were currently working on and, under the influence of LSD, we were to try to solve that problem.
DER SPIEGEL: And?
Sheldrake: I found the effects of LSD very helpful in allowing me to approach questions from new angles and imagine the relationships between plant and fungus from different points of view.
DER SPIEGEL: You attribute cognitive abilities to fungi. What makes you think so?
Sheldrake: I've been thinking about this for a while. I'm interested in the way fungi perceive their environment and how they react to it. Information is continuously flowing through their decentralized bodies.
DER SPIEGEL: What do fungi perceive?
Sheldrake: Most importantly, they have extremely diverse chemical sensors. A fungus can be seen as a large, chemically sensitive membrane, so to speak, as one big olfactory epithelium. But many mushrooms can also perceive light and they are sensitive to gravity, to changes in temperature and to changes in pressure.
DER SPIEGEL: So the fungi under our feet can sense that we are here?
Sheldrake: Some fungi would detect the pressure of our steps, yes. And now the question is, how do they process all this information without a brain and how do they translate it into behavior, into action?
DER SPIEGEL: Action? Behavior? What do fungi do?
Sheldrake: Fungi are quite active. Take hunting, for example.
DER SPIEGEL: Excuse me? Mushrooms can hunt?
Sheldrake: Yes. When food becomes scarce, some fungi can switch to a hunting mode. They build traps consisting of sticky loops or poisonous droplets. And with special substances, they lure nematodes into these traps.
DER SPIEGEL: Is this really "behavior" of the kind we see in animals?
Sheldrake: Well, we can run away from danger, fungi have to face it. Therefore, they defend themselves with the help of chemicals, or they regenerate. But that doesn't change the fact that fungi do make decisions, just as we do.
DER SPIEGEL: What kind of decisions?
Sheldrake: Fungi have many options: where to grow, what to eat, what nutrients to transport, whether to withdraw and when to hunt nematodes. Each fungus forms thousands of so-called hyphae - tiny tubes that can either grow, divide or fuse.
DER SPIEGEL: If fungi make decisions, are they also capable of solving problems?
Sheldrake: Absolutely. For example, their growth follows very efficient navigation algorithms. There are various experiments in which fungi very rapidly found the shortest route through a maze.
DER SPIEGEL: If fungi are, as you claim, complex information processing networks, are they essentially a kind of brain?
Sheldrake: No, I wouldn’t say that. But you are right: Neurons are tip-growing, electrically excitable, network-forming cells. And so are fungal cells.
DER SPIEGEL: So mushrooms have a form of intelligence?
Sheldrake: It depends on your definition of "intelligence." In a broad sense, all organisms show intelligence, albeit to different degrees. The study of cognition and intelligence arose from the study of the human mind. This resulted in a very human- and brain-centered view. I find it refreshing to extend these considerations to organisms that do not have brains. We shouldn't use ourselves as the yardstick to judge everything else in this world.
DER SPIEGEL: Is there still a lot to discover in the field of fungi cognition?
Sheldrake: Absolutely. Little is known about how fungi coordinate their behavior. We don't know the mechanisms by which they pass signals around. We've not fully understood the basic biology of mycelial growth.
DER SPIEGEL: But we do know a lot about the symbiotic relationship between mushrooms and plants …
Sheldrake: … exactly, via the mycorrhiza, through which the fungus supplies the plant with minerals such as nitrogen and phosphorus, and the plant in turn provides the fungus with energy-rich sugars.
DER SPIEGEL: How important is this symbiosis? If all fungi were wiped out in this forest floor, could the trees survive?
Sheldrake: No. They would be prone to disease, just as we would be if it weren't for the bacteria in our intestines. This microbiome keeps us healthy. In this sense, soil is sort of the gut of our planet.
DER SPIEGEL: Many ecologists are enthusiastic about the "Wood Wide Web," by which trees are mysteriously connected via the fungi in the soil and allegedly even communicate via this underground network.
Sheldrake: Yes, they actually do. There are experiments in which any direct communication between two plants - for example via gas exchange through the air - has been blocked, leaving the fungal mycelium as their only remaining connection. Then aphids were placed on one of the plants, which led the other to activate its defense mechanisms against predators.
DER SPIEGEL: Why should one tree warn the other?
Sheldrake: This only makes sense from the perspective of the fungus: It is dependent on its plant partners. If one of those partners perishes, it is in the fungus’ best interest that the other one survives. Think of the fungus as a kind of mediator that shapes the relationships between plants for his own benefit.
DER SPIEGEL: Aside from their important ecological function, what else are fungi good for?
Sheldrake: Using fungi as building material, for example, is an exciting new field. Mycelia can be grown on agricultural waste. It's fast and remarkably stable. Mycelium could replace polystyrene and fundamentally change the packaging industry. Leather can also be made with the help of fungi.
DER SPIEGEL: The next thing you'll tell us is that fungi can also save us from the coronavirus.
Sheldrake: It's possible, fungi are great when it comes to chemical protection. They have to constantly defend themselves against bacteria and also against viruses. In the U.S., there is currently a research project underway that is screening fungal strains for their antiviral properties. They are also focusing on corona, of course, but it's too early to say whether it will work out.
DER SPIEGEL: And climate change, too?
Sheldrake together with DER SPIEGEL journalists Johann Grolle and Rafaela von Bredow in London: "I suddenly discovered that this garden has a gate through which I can enter a strange and wonderful forest."Foto: Andrea Artz / DER SPIEGEL
Sheldrake: Of course! Fungi help the soil store CO2 and thus remove it from the atmosphere. They nourish plants, which helps us save on energy-rich fertilizers. We can also save fossil fuels if we use mycelium as a plastic substitute. And there’s a lot of people working to produce protein-rich meat substitutes from mushrooms.
DER SPIEGEL: Merlin Sheldrake, the high priest of fungus!
Sheldrake: (laughs) I didn't want to come across as evangelical. Of course, fungi are not the solution to all problems. But they can teach us a new way of looking at the world. Gradually we become aware how all living things are dependent on microbes. We humans have a microbiome consisting of bacteria, which in turn harbor smaller bacteria in which viruses live, which carry still smaller viruses. When we see that all life is based on these intimate connections, then it becomes clear that we can't be regarded as individuals either. We are made up of millions of organisms that work together, cooperate, compete and fight one another.
DER SPIEGEL: We are ecosystems?
Sheldrake: Yes, very complex networks. This message from the world of fungi changes the entirety of biology.
DER SPIEGEL: Has it changed you too?
Sheldrake: Yes, I look at the world differently. I have realized that the idea of the individual as a biological unit is in question. The individual is not a clear, clean category. It's more of an assumption than a fact.
DER SPIEGEL: Thank you for speaking with us, Dr. Sheldrake.