Merlin Sheldrake reveals the complexity of the fungal world
Read the full transcript of our Science Focus Podcast interview with fungi expert Merlin Sheldrake – listen to the episode at the bottom of the page.
Merlin Sheldrake: At the moment, I'm talking about the book all the time. So I'm not actually doing active research at the moment because I'm busy on the book promotion circuit.
Amy Barrett: When did the book come out?
MS: It came out on the 3rd in England, but it came out in May in the States.
AB: And what has the reception been like?
MS: It's been very encouraging. People seem to have an appetite for the subject, which is gratifying and wasn't something that I'd expected.
AB: Because the research into fungi is one of the most under researched areas, I have I got that right?
MS: Yeah, we know very little about them, relatively speaking. I mean, we still know a decent amount and there are plenty of fungal biologists. But compared to, say, our knowledge of plants or animals, we mean that we know very little.
AB: Why do you think that is?
MS: There are a few reasons. One is technological: it's only in the last few decades that technologies like DNA sequencing have been invented and have become widely applicable.
And these technologies grant us access to two fungal lives in a way we simply didn't have before. So we can grind up the DNA in a teaspoon of soil and we can work out who's there, which fungi are there. We can describe communities in different places. We can we can look at what those communities are doing. And this means that the subject of fungi has just opened to enquiry in a different way.
Then there's other reasons, too. I think taxonomically and there's been a an entrenched bias against fungi because they were considered to be plants until the 60s when they won their independence. Taxonomically speaking. And so when you wanted to study plant fungi in the past, there wasn't a Department of Fungal Sciences at university. You'd have to study it in the plant sciences department. So, it was occupying some dusty wing of plant sciences rather than being its own study. So, I think that's restrict to funds and it's restricted to students and and general expertise.
So there's a few there's a few other possible reasons as well. But those are the main ones, I think.
AB: So really, as recently as is the 60s, we didn't actually consider them to be different to plants?
MS: Well, they were considered to be fungi, but fungi themselves were considered to be a type of plant. So it fell broadly under the umbrella of botany.
AB: And so what is it about them that makes that incorrect? What is it about them that means that they're neither plant nor animal?
MS: So when you look at the evolutionary tree, the line of descent, of which fungi are a part, they make up their own kingdom of life. So it's as broad and busy a category as animal and plant, but a distinct kingdom. And they're unlike plants in the sense that they don't photosynthesise. So photosynthesis being this metabolic miracle where plants are able to eat light and carbon dioxide from the air.
So they have to do what animals do, which is to find food in the world and digest it and absorb it. But there's somewhat more like plants and animals because most of them live in a sessile way. They live embedded in their environments and have to grow places. They can't go places in the same way that animals can with their twitchy, muscular bodies.
AB: And how old are fungi as a kingdom?
MS: At the moment, the best estimates are just over a billion years. But that keeps changing. You know, depending on when new fossil evidence comes to light. A new analysis of the genetics comes to light. There's a finding from 2.4 billion years ago in lava of fossil organisms who look just like fungi. They have the same branched mycelium structure.
This is a contentious finding because it would suggest that fungi had arisen many times earlier than what we currently think. But whether they are actual fungi or just a different kind of, mycelial organism is in dispute. So we're not sure.
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AB: That word 'mycelial' – what does that mean?
MS: So when we think of fungi, most people think of mushrooms, which are the just the fruits of fungi. So most fungi live most of their lives as branching fusing networks of tubular cells known as mycelium and mycelium is analogous to the tree on which the apples grow. And you imagine how little we'd know about this apple tree if all we saw of it with the apples that pushed their way through the ground once a year and the rest was underground. So fungi live most of their lives concealed from view and mycelium is their main way of life.
AB: So do all species produce mushrooms?
MS: Very few do, relatively speaking. The fungal kingdom is enormously diverse. There's a best estimates are about 2.2 to 3.8 million species, of which we've described only about six to eight per cent of them. So we know only that much about the fungal kingdom. So of those 2.2 to 3.8 million, only about 20,000 to 30,000 produce mushrooms. So mushroom-forming fungi are in the great minority.
AB: If I'm out and I see a mushroom, that's only a very small portion of the fungus. So how far could that mycelial network be stretched underneath the mushroom that I'm seeing?
MS: Mycelium is like trees, which can vary enormously. From sort of shrubby, small trees to giant redwood sequoias. Mycelium too varies enormously. You have some fungi that form mycelium which lives as ephemeral puffs on specks of house dust and doesn't range very far. You have mycelial networks which are some of the largest organisms in the world. There's one in Oregon that sprawls across 10 square kilometres and is somewhere between 2,000 and 8,000 years old. So there's enormous diversity of lifestyle.
AB: And underneath us, what are the fungi actually doing?
MS: All sorts of things. So one of the big ecological roles that fungi play is as decomposers. So if fungi weren't decomposing the dead bodies of animals and plants, the world would be piled kilometres deep in bodies. So a lot of what fungi do in their decompositional role is something we don't notice because we live in the space that decomposition leaves behind.
We see the decomposition only by the emptiness which remains. And so it's easy for us to take it for granted. But in fact, this fungal decomposition of wood and other rotting matter is a very significant part of the big biogeochemical cycles that swarm around the planet.
So other roles they play – they have symbiotic relationships with plants. So almost all plants depend on. Symbiotic fungi that live in their roots and which lace out into the soil and which supply the plant with nutrients like minerals, like nitrogen or phosphorus and water, and also protect the plant from disease. And the plant in exchange feeds the fungi with energy containing compounds that it's made in photosynthesis. So sugars or lipids, for example.
And this relationship is very ancient and really lies at the root of all recognisable life on land because the ancestors of plants would not have made it out of the water were it not for these alliances. These ancient alliances with their fungal partners. So that's another major role that these fungi underground will be playing.
AB: So they wouldn't have made it out of the water because they wouldn't have been able to take these nutrients from the soil themselves?
MS: Yes. So the ancestors of plants would have been that freshwater algae, sort of puddles of photosynthetic tissue used to stewing in a nutrient broth, a watery nutrient broth, which would have been their home. And as they washed up onto these soggy shores of lakes and rivers, they faced a new type of challenge. There was light and carbon dioxide in abundance.
But to scavenge their nutrition from the ground was something they'd never had to do before. And fungi are masters at this kind of scavenging. And so at this point, the fungi and the algae sort of struck up a relationship and the fungi would have behaved like the root system of these early plants. And in fact, plants didn't evolve roots for another 50 million years.
So fungi behaved as plants' root systems for 50 million years until plants could evolve their own.
AB: You've mentioned there was a fungi-like creature found in lava. Is it that fungi can live in places where no other organism could survive?
MS: Yes. So you have fungi living in extreme environments, for sure. And there are other organisms that also live in extreme environments. There are various types of bacteria or archaea, which are also very extremeophilic. But fungi can live in unusual places in some ways because they form lichens, which are a symbiotic organism made up of a fungal partner, or several fungal partners, and a photosynthetic partner or several photosynthetic partners.
And lichens, you'll have seen them, those tufty scaly organisms that coat fence posts and roofs and gravestones and walls and tree trunks. These lichens can live in extremely inhospitable places because the fungus and the photosynthetic partners, they form a kind of micro ecosystem. A summary of life on Earth with the fungus doing this digesting, and the photosynthetic organism doing the photosynthesis. And together they make a little biosphere and can survive in the most unexpected places.
So when a volcano throws up a new island in the Pacific Ocean, lichens are some of the first things to move in. And they can make a life on this bare, solid rock. The fungus can digest minerals from the rock and the photosynthetic partner can make energy from sunlight. And so you would find lichens on these very newly exposed surfaces. You'd also find them prospering as crusts on the scorched ground of most deserts where they stabilise the surface of deserts. So lichens are very fascinating creatures with very extreme tastes.
AB: Do you find any fungi in the sea?
MS: You do, yes. Relatively little is known about marine fungi, but there are fungi found in samples of sulphurous sediment taken from far below the surface of the ocean. And there are fungi that weave their way through coral reefs and live on the bodies of marine crustaceans, amongst other places.
AB: That's amazing. And for you, what is it like to be a researcher looking at fungi? Do you get to go and see them all over the place or do you find that you're sitting in a lab?
MS: So when I was doing a lot of my work in Panama, in tropical forests in Panama, I was studying these relationships between plants and their symbiotic root fungi or mycorrhizal fungi as they're known. And I would be in the forest a lot. I would be taking samples in the forest. I had also experiments in greenhouses, growing plants with different types of fungus and seeing what happened to them.
And then I would also be in the lab dealing with these samples. But then for writing the book, when I was writing the book, I travelled much more widely and I went to visit lots of different people studying fungi from all sorts of points of view. And from excursions I had a much broader range of experience, including, for example, truffle hunting in Italy with some very secretive truffle hunters who search for the very prized and elusive white truffle which has never been cultivated and so has to be found in the wild.
AB: What is different about truffles? What makes them so desired?
MS: In some senses, because the truffles have made themselves desirable, because truffles are the underground fruiting body of certain types of fungi, root fungi, mycorrhizal, fungi. But underground, these truffles, these fruiting bodies, they're unavailable to wind currents that might spread their spores if they're a more conventional mushroom. And they are invisible to the eyes of animals.
And so they have to spread their spores. They produce these very amazing aromas which can filter through the damp soil, travel through the air in the forest and catch the attention of an animal who will then go out of its way to find the truffle, dig it up and eat it and then carry it's spores away and deposit it in its faeces in some other place.
So truffles have made themselves attractive because their lives depend on it. And so you can think of these truffle aromas really as an evolutionary portrait in scent of animal fascination. And humans are part of that animal fascination like shrews, squirrels, pigs, dogs, mice, everything else that eat truffles. We do, too.
And some of these truffles, like the white truffle, have particularly prized flavours. And so humans dig them up and have whole industries built around them. They have to be served on a plate within about 48 hours of finding them in the ground because that aroma is made by a living process. So you can't dry a truffle. So humans have developed special packing chill to transportation systems, ways of rushing them through customs and getting onto plates in other countries, all within 48 hours or so.
So we do a lot to disperse these organisms. In fact, we urgently disperse these organisms because their flavours are so attractive to us.
AB: Why is it that they can't be cultivated then?
MS: Some of them can. Some types of the cheaper melanosporum or the perigord black truffle can be cultivated with some degree of success. The white truffle, it's very hard because we don't understand enough about how it forms relationships with its host trees. So you can get a host tree to have the mycelium of this white truffle growing on its roots. But when we plant that out in in a natural environment, then it just won't fruit.
So we don't understand what it is that this symbiosis needs in order to fruit. There are too many variables. We haven't got this in hand yet. And it's mostly because we don't understand the sex life of these truffles. It's all about these different relationships. The truffle's relationship with the tree. The truffle's relationship with other truffles of the opposite mating type. So there is a cascade of relationships that humans are struggling to understand.
AB: Aside from the truffle, obviously we know of yeast, but are there any other fungal species that we interact with on a daily basis?
MS: Yeast are a big one. We have yeast coating our body. We have yeast living inside us, lining our orifices. Yeast play a major role in human culture, baking and brewing, being major examples. So, yes, yeasts are often an underrated agent in human life and the history of civilisation.
But apart from that, every time you interact with a plant, whether you eat it, you plant one, you buy one. There are fungi involved in that plant's life from the beginning until the moment you eat it. Most plants have fungi living in their leaves and in their shoots as well as in their roots. And so plant life is also fungal life. And of course, people eat fungi for food, mushrooms.
But then in the world of drugs, fungi pay an enormously important role. So penicillin is a very famous story where a mould, as part of its antibacterial defence system, produced this compound, penicillin, which humans were able to repurpose and use to defend ourselves also from bacteria.
But there are others besides, there's cyclosporin, which is a immunosuppressant drug which makes organ transplants possible. There's statins, the cholesterol lowering statins. Taxol, the blockbuster anti cancer drug, psyilocybin, the psychedelic recently found to alleviate anxiety and depression. So there's a very long list of drugs derived from fungi which really play a major role in society.
AB: But there are of course fungi that are dangerous to us and animals.
MS: Yeah. There is some poisonous fungi, which means if you are foraging for fungi, then you need to be very sure that what you're picking is what you think it is.
But fungi have a reputation for being poisonous, which is perhaps disproportionate to the number of poisonous species that there are. But foraging for mushrooms, you do have to make sure that you know positively what you are eating. They call it positive identification, rather than knowing that it's not that, it's not that, you have to know that it is this. So poisons is another thing that they do.
AB: On foraging, what's different about the ones that we would go out and forage than the ones that I might buy in the supermarket?
MS: So, on the whole, supermarket mushrooms are a species called agaricus bisporus, and cremini mushrooms, those supermarket button mushrooms, and portobello mushrooms – they're all the same species of mushroom just at different life stages. So it's a clever racket that has been developed to pass these off as actually different mushrooms when they're just the same species at different points in its lifecycle.
So these mushrooms are some of the less nutritious and medicinal mushrooms around, but they're just very easy to grow. So they were some of the first that people were able to cultivate on a large scale.
But there are many other types of mushroom which are also cultivatable, which you can buy in different shops, too and a growing number of supermarkets like shiitake, lion's mane and oyster mushrooms, and these are more medicinal and more nutritious as well. So mushroom cultivation is really booming right now. And hopefully we'll see more and more diversity of mushrooms in our shops as this continues.
AB: And how far back in human history does our relationship with fungi go?
MS: Very far back. I mean, as long as we've defended on plants for our nutrition, we've also depended on fungi. So you can go right back to long before humans were humans. But then there are lots of other examples of involvement of fungi in human history. There's a study that came out quite recently which analysed the tooth plaque enamel of some Neanderthal skeletons. And one of these Neanderthals had a tooth abscess, judging by the state of its teeth and this individual, and not the others, had been eating an antibiotic producing mould which suggested knowledge of its medicinal properties.
This is tens of thousands of years before. Alexander Fleming discovered penicillin. So fungi use in medicine stretches along way back. As a fire starter, as a way to hold fire, a kind of tinder and a coal holding material, a way to transport fire, played a very important part as well.
And as psychedelics in some cultures in middle America, the use of psilocybin containing mushrooms as a sacrament, as a cultural tool of experiencing all sorts of non-ordinary states of consciousness, mushrooms stretch back to 3,000 years at least. So there's a there's a long entanglement of human lives and fungal lives. It's not going to stop either.
AB: What does the future look like for our relationship with fungi?
MS: There are all sorts of fascinating possibilities and fascinating realities happening really quite quickly. So some fungi produce these medicinal compounds and a mycologist called Paul Stamets in America has found that antiviral compounds produced by certain species of fungi can help bees to overcome colony collapse disorder, which is a really major threat to all human life on the planet. And if you feed these bees with these medicinal extracts from fungi, then they live for much, much longer time. So that's one avenue, a kind of medicinal wing of the medicinal mushroom story but applied to but applied to bees.
There are other aspects of medicinal fungi that will play really important roles as anti cancer drugs, antivirals, antibiotics and immune-supporting compounds. It's a huge and rapidly expanding field.
And then as building materials, you can encourage mycelium to grow in damp wood, sawdust, sort of ground corn stalks, agricultural waste, basically. And you can create blocks or boards a bit like wood composites. And these can be used in all sorts of places. IKEA are re-envisaging their packaging as mycelial packaging. Dell, the computer company, already ship thousands of servers a year in mycelial packaging.
A leather-like material made from fungal mycelium is picking up speed and looks set to revolutionise the fashion industry. And so these are really exciting possibilities and will help to disrupt some of the really polluting industries and use renewable materials in their place. So, these are just a few of the ways that that humans are striking up new types of relationship with fungi.
AB: And will climate change have any impact on fungi?
MS: Absolutely. Yeah. So there will be a number of fungi which are forced into very difficult situations because of climate change and the range shifts of their host plant species. Some will adapt. Some won't.
For example, as plants are forced to move up or down latitudes because of climate change, their fungal partners will either be able to make that journey with them or not if the plants aren't able to move themselves.
Lots of fungi will thrive in disturbed environments. So during the last major extinction, the one that wiped out the dinosaurs when an asteroid hit modern day Mexico. The blankets of ash that covered the planet killed off a lot of the forests, and so this global compost heap was a fine breeding ground for all these decomposing fungi who had a kind of field day, a field period, when there was just huge amounts to decompose. So decomposers thrive in this kind of disturbed environment. Some fungi will not thrive in that kind of disturbed environment. So there are many ways to be a fungus in many ways, fungi to respond to global heating and environmental breakdown.
AB: So will fungi outlive us?
MS: Well, I would say almost certainly.
AB: And do you ever see that there could be a world without fungi?
MS: It would not be recognisable to us, certainly. So, if you look back in the history of life and imagined replaying the tape of the history of life without fungi as part of that story, there would be life. But it would be totally unrecognisable. And we certainly wouldn't be here. And so moving forwards, it's very hard to imagine a world without fungi either.
AB: And for you, what would you say is so fascinating about fungi, why have you chosen them to focus on?
MS: There are so many reasons. I find that thinking about fungi makes the world look different. These organisms have the power to change the way that we think and feel and imagine. For example, when you realise that the underground between plants, there are these large networks through which all sorts of nutrients and materials, water and signals are passing. When you realise that the history of life is a history of symbiosis in which fungi had played major roles, then things start to look different.
When I walk around outside, I experience it differently knowing that this is going on. So I found this very fascinating and also fascinating because it helps me to understand these seething, entangled networks, which really is how life works. So when you think about ecology, which is the relationships that formed between organisms and their environments and organisms and other organisms, these fungal networks form literal, enduring, persistent connections between organisms.
They embody this basic principle of ecology. And so I find them really helpful organisms just to keep my attention on the relationships between things, and on the interconnectedness of these life forms. And so it helps me to keep that picture large and to avoid tunnelling too rapidly into narrow, reductive stories.
AB: And fungi can help trees communicate between each other, right?
MS: Yes. So the fungi that helped plants and the ancestors of plants out of the water, 500 million years or so ago. These fungi don't just form relationships with one plant. They're promiscuous. And so they can form relationships with more than one plant. And plants are also promiscuous and can form relationships with more than one type of fungus.
And the result is these overlapping, shared fungal networks shared between plants and as well as nutrients which can pass through these networks, there have been very good studies that show that you can have the signalling compounds passing between these between these plants.
If you have two plants grown next to each other and they're either allowed to share a fungal network or they're not allowed to share, and you expose one of those plants to aphids, which are a pest. You don't expose the other plant to aphids. Then the plants that share a fungal network and then the second plants, if they share a fungal network will regulate its defensive responses, although it has not itself experienced the aphid attack, which indicates that somehow through the network, information is passing. Exactly in what form this information is passing, we're not yet sure, but it's very clear that it does take place.
AB: I think lots of us have taken to gardening more recently, than we might have done in the past. Should we be considering the fungal composition of our soil, in my house plants?
MS: Well, I mean, I personally find it helpful to do so. And in reality, in one's garden, most people probably aren't applying a huge number of chemicals and inorganic products, which would potentially disrupt the fungi. If you're going to spray your garden with fungicide, of course, that would really interfere with these symbiotic relationships that the plants need to survive. And that would be if you're spraying your garden with fungicide, and you find out about this symbiotic fungi, then maybe it would be helpful, maybe you might choose to not spray the fungus side on your plants, and that could be you make a difference.
But I think probably for many people who are gardening, who aren't using these methods and there's not been not much that you would do differently apart from really attend to the health of the soil. And compost, for example, is really good for these relationships rather than chemical, inorganic fertilisers.
But just knowing that these plants that you can see growing in front of you are growing out of this relationship, that what you see is the outcome of one hundreds of millions of years' old relationship, that these plants are, in fact, algae, which have evolved to farm fungi and fungi that have evolved to farm algae. You know, this is a really big thought for me at least.
AB: Do you have a favourite species?
MS: Oh, no, I'm terrible at favourites, it depends on the day of the week and weather. Today, I'd say Maitaki, which are really beautiful, Hen of the Woods as they're sometimes known. They're very delicious mushrooms that are also quite medicinal.
AB: So when I'm next out on a walk, what can I look for in order to appreciate the fungi that maybe I can't see?
MS: So you can look for mushrooms, that's one thing you can easily do. And looking for mushrooms is something you sort of open your senses to. You know, sometimes you can just see them growing. But if you're really looking for them, you can walk slowly. You can slightly blur your eyes to give you a bigger field of view. Mushroom hunters describe 'getting their eyes on', you know, "I haven't got my eyes on yet, so I missed that". And so it's quite fun to to try and drop into that state.
And apart from mushrooms, there's lichens. Lichens are very common and most of the time we pass over them without giving them a thought. If you see lichens growing, then an even better if you look at lichens with a small hand lens, they become worlds, total continents, on an unfamiliar atlas. Astonishing to get lost in their forms and colours. So that's one way.
And any time you see a plant, you're seeing the outcome of this fungal association. Rotting, anything decomposing, rotting logs and any when you see fallen autumn leaves and you lift them up and you see where they're becoming soil, that frothing wilderness of decomposition and microbial activity. So there are all these different ways that we can learn to notice fungi.
AB: And there's any life lessons that we can take from fungi, what would you say they would be?
MS: Fungi raise lot of questions. So one question that they raise is to do with individuality. We're used to thinking of ourselves as neatly bounded individuals and fungi can make questions of some of the categories that we use to organise our lives. Now, given a piece of a fungal network, a mycelial network, you can take any fragment of that and it will turn into an entirely new mycelial network. And you can do that potentially forever. So under the right conditions, you can think about these fungi as immortal.
But these fungal networks can also fuse other fungal networks to make larger fungal networks. And so where does one start and where does one stop? And you have a fungus living inside an insect and changing its behaviour, which they do sometimes. And you have this astonishing fusion of a fungus with an animal and behaving in a new a new kind of way. And so lichens as well.
You know, these are composite organisms expressing themselves in ways that they would not do if they were growing alone. And like the chemical elements of hydrogen and oxygen which come together to make water, which is completely unlike hydrogen or oxygen, both of the explosive gases. Lichens come together to form these organisms, which are completely unlike their constituent members.
So these fungi play games with individuality that really challenge us to think about how it is that we impose our categories and concepts on the world.
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Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.