Togetherness: How co-operation built the world

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0:37Hi, Benjamin here. Welcome to episode 15 of Nature Hits the Books. In this episode, I'm joined by science journalist Rowan Hooper, who is podcast editor at the magazine New Scientist. Rowan's new book, Togetherness, Symbiosis and the Hidden Story of Life's Greatest Collaborations, takes a deep dive into the world of cooperation between organisms, arguing that, although in many cases perhaps under-researched and under-appreciated, working together in symbiosis has been as important a driver for making the world the way it is as the classic evolutionary idea of competition. The book looks at the array of intimate symbioses that exist between organisms across the tree of life, their importance to ecosystems how human activity is affecting them and how researchers could adapt them to tackle global problems just a few of the things we talked about in this podcast

1:45rowan hooper thank you so much for being on nature hits the books hey great to be here thanks for inviting me Ben. Let's talk about your book then. Symbiosis is the topic all the way through but I think it'd be good off the bat to lay out what it is and what it isn't. Yeah because it's used in a sort of non-scientific way so much the word symbiosis but scientifically it means living together but then that can be for a long time for a short time how intimate does it have to be so I've defined it as two different species that live together for an extended period of time in an intimate way so this isn't like a bee coming and pollinating a flower and then flying off and it turns out to be incredibly widespread it's all over the place all over the world and it happens at every stage of life so it's an incredibly important process and phenomenon and your book is peppered with examples of this now i have a fig tree in a pot on my patio and i think the fig tree and the fig wasp is perhaps the classic example of a symbiosis and one that you start your book with it has to be said yeah i think a lot of folk will have heard of this but i think the example of this symbiosis shows the incredible intricacy of these things and this relationship has taken an unfathomable amount of time to come into existence maybe you could just lay out for folk who haven't heard of it what this symbiosis is so i can't remember how many hundred species of fig there are but everyone has its own species of wasp that it relies on to pollinate it and the fig wasp only is attracted to that particular species of fig tree it goes into the fruit so inside the fruit are the flowers that point inwards the fig wasp has to crawl inside the fruit pollinate them and then it dies and then the larvae grow inside the fig so the fig that you have in your garden though will be one of the few species that's wind pollinated but all other figs and they're really important species in forests all over the world are pollinated by this very specific, very tight and, as you say, very anciently evolved form of symbiosis between the fig wasp and the species of fig.

3:52And there are layers to it as well, right? Yeah, it is quite a gruesome, well, it's incredibly strenuous. What the fig wasp has to do to get into it, once the wasp is inside, it's maybe had to break off some wings and its antennae to fit in and the tunnel entrance into the fig is blocked. The wasp can then move about and pollinate and then it dies. And then what happens, the larvae develop inside the fig and then the males hatch first and they go around and they copulate with their sisters while they're still in their larval form. Then they cut open a hole in the fig and then the sisters come out, like emerge out, already fertilised and crawl out and fly off to start the cycle all over again.

4:34And this is but one of a number then. Which one of these symbioses stood out to you the most? Which one blew your mind, would you say? I mean, it changes all the time. At the moment, I've been really delighting in seeing a whole load of orchids near my house in West London here. And orchids, one of the most successful groups of flowering plants, 28 ,000 species, every single one of them relies on symbiosis to grow. So these beautiful flowers, they only grow through symbiosis with fungi. One that I was for many years desperate to find is the solar-powered sea slug, which lives off the coast of the UK.

5:10It lives around the US as well, around the Florida coast there. It's a sea slug, but it extracts chloroplasts from the seaweed it eats and then incorporates them into its body where they carry on functioning. So they convert sunlight into sugars that then the sea slug can use. So it is literally a solar-powered sea slug. And when I found one of those, I was absolutely delighted. And examples of these really hand-in-glove relationships where both parties take something, give something, are found across the tree of life. But getting to the point where scientists could agree that this was a thing took a very, very long time.

5:49And I think one that you talk about is the rift in lichen research, which is maybe not the place you'd expect this. lichen are a wonderfully diverse group of things i suppose you might have to call them you find them all over the place but working out what they were or are was a real argument yeah it was scandalous really when people started proposing that lichen was a symbiosis between a fungi and an algae that come together and grow the lichen that we are all familiar with the lichenologists and there were many of them were absolutely up in arms at this they did not want to surrender what they saw as the status of the lichen to be this dual organism.

6:28There was a battle that raged for some decades, really. And eventually, the evidence just became overwhelming. And it's something you see throughout other examples of symbiosis around the world, is that many people resisted the evidence. They didn't want it to happen for some reason. But as you say, yeah, it was the first case. And the word symbiosis was actually coined to describe what the situation is in lichens you know in the late 19th century and so yeah the lichens were the battleground where symbiosis was first established and like while we're on lichens people might just think well you see them on trees on gravestones whatever but they're a really incredible pioneer organism that really helps develop the soils on fresh rock so when organisms first came out of the sea and we first had to start growing on land there was no soil but lichens were one of the most important groups of organisms that helped turn rock into organic matter that could then be used by plants to come along and grow so incredible pioneer species incredibly beautiful diverse as you say and all to do with symbiosis and this idea then that cooperation is really really important is something that you come back to again and again now charles darwin clearly is very very important to you as well right you mentioned him a lot yeah during this book the idea then that cooperation is what made the world what it is is clearly at odds with his theory of evolution that competition is king yeah i suppose now you know that darwin himself was clearly aware that cooperation was happening but it's something that clearly confused him even though he hints at it heavily at the end of his book on the origin of species yeah yeah there's a famous ending where he talks about the entangled bank and he paints this beautiful picture of life forms building basically a web of interconnected dependence.

8:19And that's how he chose to end the book. There's also examples throughout The Origin of Species where he talks about what we would now call ecology, although the word hadn't been coined in Darwin's time. So he did understand ecology. He did experiments in his garden that were ecological experiments. He thought in ecological terms, but he emphasised, as you say, the competitive nature of how he saw evolution working. Of course, competition is important. I'm not saying that's not the case at all. But what he deliberately did was emphasise the competitive side of things, because that's what people saw around them in the world that he was publishing his book in.

9:01It was at the height of the Industrial Revolution. Capitalism was really up and running. People thought in competitive ways. And Darwin was very, very aware of how his book would be received and he wanted it to be a success so I think he emphasised the competitive side of things not just because it is important and it is part of it but that he knew that that would make the book be better received and it was in fact it's been too well received and then it went too far people then started using Darwinism as a justification for how they saw society should run. And it was used as a justification for capitalism and for exploiting the natural world.

9:45But that's not what Darwinism is actually all about. It's just what it's been sort of represented as. And certainly in The Origin of Species and in a lot of his work, there are all these examples of interconnectedness and a web of life. And if that's kind of his opus then, I mean, you do take a diversion into Charles Darwin, the post-college years as well, when he was pulling all this stuff together. Clearly a very fertile time for him and lots of ideas floating around. Why did you choose to have a look at this? Well, I was fascinated when I found out that he lived in Soho in London. I was amazed because I'm an evolutionary biologist, so I thought I knew quite a lot about Darwin.

10:24But it turned out, really, I only knew about his voyage on the Beagle when he was a very young man. And then the picture we all have of him as an old man with a long beard living in Down House in Kent. But in between those, when he got back from the Voyager of the Beagle, he lived as a bachelor next to his older brother. And they went out on the town, probably quite similar to what people do now. He was soaking up all the ideas that he could find in London. He was writing up his work from the Beagle. And the reason I particularly focused on the years he lived in Soho was that was the year. So I'm wearing this T-shirt, Darwin's sketch of the Tree of Life.

11:03This was the time when he first drew this sketch, which is first started to show the ideas of evolution. Until then, he didn't quite have a mechanism for how his ideas would work. And then he read Malthus, which was about how a growing population would exert pressure, which would, as Malthus saw it, select out people who couldn't survive. Darwin realised that that pressure that Malthus described for humans would apply across all of life. And it was a pressure than he could put into his theory of natural selection. So there was that. And he also met Charles Babbage at this time. It just blew my mind again that Charles Darwin became friends with Charles Babbage and started to see demonstrations of this prototype computer, an analog computer that Babbage was building.

11:49And I just make the point in the book that I think that Darwin took a lot about the mechanized nature of this proto-computer and how that would operate. and I think that helped inform him as he was thinking about how natural selection could work in other words there was no need for some sort of divine intervention to explain how species came to be which was the only way people were thinking at the time and of course when his book eventually comes out I don't think it's unfair to say it turns the world upside down yeah and we've talked there that you know he did know that it wasn't necessarily like this competition wasn't the end all and be all the only game in town because as I say like he was confused by some of the things that he saw.

12:28But aside from Darwin, you look at a lot of maybe the forgotten scientists who did have this idea that the world was much more interconnected, but not just scientists as well, poets and artists. So there are folk who are thinking, dare I say, in a more holistic way about the world. Yeah, well, it's funny you say, dare I say it, because I would have also thought in those terms as well, just tentatively, as if as a scientist, it's a little bit of a dirty word. And it has been for a long time and probably still is in many labs. But poets, sure, didn't have any problems thinking of the world holistically.

13:00They intuited that we can have a oneness with the world, a feeling of connectedness with nature. Whereas showing that scientifically has been not only really difficult, but also the reason people have shied away is that it does feel basically a bit hippy-dippy-ish. That's slowly changed, though. So we've talked about lichen. Lichen is the classic one. Coral is another organism that is a symbiotic organism, this time an animal and an algae living together. And it just doesn't make sense to think of coral without thinking in holistic terms, these two species coming together. It's greater than the sum of its parts.

13:39So it's necessary scientifically to think holistically, certainly for a lot of groups of organisms. And you use the term holobiont a lot when talking about this kind of situation there, greater than itself kind of thing. Yeah, so the holobiont, when you see a coral, that's what's created when the two species come together and form something greater. For us, we are a holobiont because we have our own trillions of microorganisms living on and in us. So it just makes sense. It's just necessary to think of the holobiont, This collective of all the organisms that make up one sort of mobile ecosystem that we call ourselves.

14:19That's an interesting one. I mean, as a former microbiologist, I do think that the idea of what one's self is has changed. It's not a very long time that folk have really been looking at the human microbiome. I think it's fair to say there's yet to be the smoking gun that this microbe leads to that outcome, whatever it may be. but there certainly is a growing body of evidence that really we are vessels in a way that we interact with the things that live inside and on us as well I guess. And it's not just that it's that we develop with those organisms as well I think that's another really important point many organisms cannot grow without the interaction from the beginning with another organism often bacterial so there's a great example of the bobtail squid this is very cute little squid that grows very intimately with the specialized bacteria that it sequesters from the ocean around it they grow very intimately together and it literally wouldn't grow the same without these bacteria that it gets but it's the same with lichen again the fungus won't grow into the lichen pattern without having the algae they develop together this hollow biome that's produced is something that you just can't get on its own so it's not just morphologically different though as well you get these functional differences and often you get this situation where both partners in the symbiosis get something they couldn't have got on their own they get access to something that was unavailable as a singleton so that's why they persist these symbioses over evolutionary time and one that demonstrates this closeness then is the relationship between plant roots and what's going on underneath the surface of the soil there are so many symbioses that it's hard to measure right yeah there are like i think one of the revelations i had was i was visiting a scientist who showed me his experimental farm and there were all these fava beans growing and so legumes things like beans pulses lentils they form this symbiosis underground the roots form these nodules with bacteria which make fertilizer for them by taking down the nitrogen from the atmosphere and turning it into ammonia because plants otherwise can't get access to nitrogen in a biologically accessible way so the bacteria do it for them and the scientist just pulled up one of these fava bean plants from the ground and knocked off the soil and i saw all these nodules all over the roots just right there there's symbiosis that was just a great example straight away of what's happening with all legumes all over the world but the other main symbiosis which 80 percent of all plants has of course is with fungi underground this network of mycorrhizal fungi that plants tap into and that is just unbelievably extensive all over the world and vitally important to the plant and the fungus and in many cases these symbioses come together like the squid there takes up the bacteria from its environment but in many cases symbioses are passed down like they're seeded in a way if we can use a plant metaphor i suppose between generations because they are so tightly entangled that the two individual parts cannot exist at all unless the symbiosis is there yeah so sometimes they are physically passed down to the generation so that a spore will be passed down with a piece of algae or other times it's more of a bit of a free-for-all it's just chucked out there into the environment and then the offspring have to then pair back up again with their partner.

17:47So a coral polyp will have to swim around and find the right kind of algae to grow with and make a new coral. The same with orchids. Orchid seeds are just tiny, tiny particles of dust that just blow around. They don't have resources in them like an acorn or a seed that we might be more used to. So they just blow around and they have to effectively hope that they land where there's some fungi that they can instantly form a symbiosis with and start growing so that's why orchids make millions upon millions of seeds because most of them won't land where there's the right kind of fungi to grow but some will and then the orchid gives a home i guess inverted commas to the fungi and the fungi provides the nutrients that the plant needs yeah so the fungi will provide the starter pack for the seed to grow and then as soon as the seed sends some shoots up starts producing sugars through photosynthesis then it will send some sugars down to the fungi as payback for the start that the fungi gave the orchid in life so we've talked a lot about darwin and evolution i mean let's take it way back in terms of evolutionary time if we can life as we know it exists because of symbiosis not necessarily because of the way the land has been changed by a lichen but literally the mitochondria the batteries inside of us that let us do what we do that is perhaps one could argue the most important symbiosis certainly for me i think is one of the most important that came to be and it's been a hard one to study yeah so this is another one that there was a huge battle this time raged for i don't know 60 years or more the idea that all complex life that means us trees mushrooms fish all complex life forms have mitochondria in the cells that provide the energy molecules that our cells run on and the idea that these mitochondria were themselves originally bacteria was put forward maybe over 100 years ago but it was rejected people were abused for daring to say that this was happening and it only finally got over the line in the 60s when lynn margulis the american microbiologist she was able to marshal enough evidence to silence for once and for all the doubters it was finally enough to get it over the line to understand that about two billion years ago our ancestors absorbed the ancestor of the mitochondria and instead of digesting it kept it inside its cell and it became the first bacterial power pack in this first complex cell from which came all of complex life and this was by no means the only time this happened chloroplasts right in plants that ultimately turn light into food is another example of this and events like this say happened potentially billions of years ago and working out what happened is very very hard to do without the sort of advent of time travel yeah but you do talk about how folk have maybe caught similar things in the act which might give an idea of how events like this happened so you mentioned chloroplasts they were cyanobacteria that was incorporated into the ancestor of algae to use inside their cells where they carry on photosynthesizing and this time though the sugars that are made through photosynthesis are given to the bigger cell.

21:01So that happened at least a billion and a half years ago. And it's had all that time to be fully integrated into the plant cells. So it works very smoothly now. But scientists have found a couple of occasions where you can see a symbiosis which happened more recently, a cellular endosymbiosis, it's called when one life form is absorbed into the cell of another one. But it hasn't had this billion year time to get integrated. It's happened much more recently, only maybe a few million years ago. So in chloroplasts, a lot of the genes in the original cyanobacteria have been transferred into the nucleus of the algal cell.

21:41So nuclear control has been wrested from the cyanobacteria. In more recent examples, that control hasn't switched over to the nucleus entirely yet. So there's still maybe a tug of war going on over evolutionary time and the integration hasn't happened. But yeah, it does show, well, this is something that takes time to get fully integrated. And you can imagine often it won't have worked at all. Maybe it started to happen and then the line just died out. But the line that's led to all of complex life with mitochondria and chloroplasts in plants, that has done spectacularly well, of course, and diversified all over the world.

22:19Right. And you do actually go back even further than that as well. Well, and you talk about how the mitochondria example was controversial. I think what you write about, the research about how life arose at all being a symbiosis will be controversial, I'm sure, for a long time to come by many folk. But it is being looked at. Yeah, it is. So the reason I got onto this was the physicist Freeman Dyson wrote in the 80s. He was familiar with the work of Lynn Margulis, who, as we said, she was the one who finally got it over the line, the idea that mitochondria were originally a bacterial cell that was integrated.

22:54And he thought, well, maybe there was something going on like that at the origin of life. But instead of a mitochondria and another cell, it was information and metabolism that came together. So you can imagine like maybe a strand of DNA and a metabolic protocell, which doesn't have any DNA, but where there was metabolism going on. These two kind of proto-life forms might have come together, Dyson speculated, and that was the origin of life. So that was his idea. And people started looking at, well, how might that play out? And we know that you do get proto-cells forming, especially in hydrothermal vents, where you get a lot of reactions going on in these cells, which are metabolic reactions happening without there being any instructions to specify how to do it.

23:48It just happens because of chemistry in the hydrothermal vent. So if you're in that situation, it could suggest, like Dyson thought, that if you've got a replicator coming in, like a piece of DNA, it could then start replicating inside the protocell, and then it could move along and become a life form. What it's currently thought of now is that it's not quite as Dyson thought, but that these reactions going on in the protocell themselves sometimes contain bits of nucleic acid. So the nucleic acid was part of the metabolism. And then that could itself then start coding for things to happen, like for proteins to be formed, which would then help the metabolism more.

24:30So there is a pathway being laid out. And as you say, it's controversial. It's by no means proven yet. The origin of life is not proven yet. But I think it's really promising, a fascinating story. And it just works brilliantly for my larger book idea that symbiosis has this role, not just throughout all life and all ecosystems, but even perhaps at the very origin of life too. Obviously, this is kind of your thesis then you're putting forward, that really this is more important than maybe people give credit for. But I have to say, I found the end a little bit bleak, Rowan, because I think you make the point that these symbioses are so fragile, so specific, that even a nudge could undo them and lead to conclusions we don't know yet.

25:15And one can't help but realise that humanity is leaving its dent on the earth right now. And I think the one you write about is ants and acacia trees and how that could unravel. So this is in East Africa. The ants have evolved a symbiosis where they live on the acacia trees. is they live in particular little domains that grow on the tree. These are thorn trees. And if an animal tries to come along and feed on the tree like an elephant, the ants will swarm over it and bite it. And, you know, even a big elephant or a giraffe or a zebra doesn't like being bitten by loads of ants and will go away.

25:47The reason that is sometimes broken down is that an invasive species of ant has come in which has knocked out the symbiotic one that doesn't have the protective effect. that means that the elephants can then feed on the trees because the ants don't bother to protect it and that then has a knock-on effect on what predators can come in and so on so it has a real knock-on effect on the ecosystem but that's not actually the problem i'm more worried about the problem is nudge is a too mild a word for what humans have done to the ecosystem we've given it an absolute pummeling so the two biggest problems are with coral and the symbiosis in corals is breaking down because of coral bleaching because we've heated up the oceans by so much the symbiosis can't cope with it and so you get the deaths of corals and the other one is the overuse of fertilizer which knocks out the symbiosis that you get underground that we've mentioned already so the ones that help plants get nutrients if you add nutrients already if you add fertilizer like we do in immense quantities, then the plant doesn't need to form this symbiosis.

26:56So it doesn't bother forming it. It just relies on all this fertiliser that we're pouring onto the fields. And then it kind of forgets how to form these symbioses. And then you become ever more reliant on pouring more fertiliser on. That has a huge effect on greenhouse gas, as well as pollution when the fertiliser runs off. So those are the two really big problems I think we have with losing symbiosis. So I didn't want to sugarcoat it. So there is this bleakness, but the whole point of the book though is to try to redress the idea that our society is one that's based on competition or that nature is something that is based entirely on competition.

27:37There's also all this symbiosis and cooperation and it doesn't mean that we should live our lives how we thought nature worked by exploiting and competing and running amok over everything else. You finish off with a bit of future gazing, which is always fun from a scientific perspective. And some of the things that you write about maybe will come to fruition. Many of them won't, I'm sure. But awareness that symbioses can bring different things to a party, I suppose, is something that researchers understandably are looking to take advantage of, to piggyback on. What are some of the things being done in that sphere?

28:13I think the most exciting thing is to try to get the trick that legumes have of making their own fertilizer into cereal crops. So like wheat and maize and rice. If we could get those crops, which provide vast amounts of nutrients to the world, most of the calories we need, if we can get those crops to make their own fertilizer, that means we don't have to use this incredibly polluting and damaging synthetic fertilizer on our fields. it would be a really incredible breakthrough and people are trying to do it and they're having some success it's getting there i think it will get there it's just how quickly we can get it there how quickly you can get it rolled out and it seems like they're coming together of a lot of different branches of science so you've got ecology of course you've got microbiology you've got synthetic biology programming inverted commas organisms to do things that they might not otherwise do yeast for example i mean this is probably getting a bit more down the road but But if you can start making your own yeast, you can make a kind of synthetic lichen.

29:16So if we have a synthetic yeast, you'll be able to program it to do what you want. So, for example, you could make a yeast which makes pharmaceuticals or you could make biofuel, something like that. And then you put that with an algae and the algae will then make its own sugar and feed the yeast to make the product you want. But you're making it sustainably because you're making it using photosynthesis. That's something people are doing. People are already making synthetic lichen. And as we get better able to program synthetic yeast, then you can really start to think, well, we could do more ambitious things, maybe even sequester carbon in larger amounts than we're currently able to do.

29:55So that's a little bit further down the line, I think, than the fertilizing crops. But it's something that I just wanted to mention at the end just to look forward at these things that you could do. Let's have one more then. And obviously there's lots of examples of unusual symbioses in your book. In the lab I used to work with, we had a colony of leafcutter ants. And tell me about their symbioses, Rowan, because they've been farming for millions of years. Well, so ants do everything, right? I went to Brazil to research the book and I found one night I was walking in the forest and I saw this commotion and it was leafcutting ants stripping a bush and walking back to the nest, carrying thousands of fragments of leaf.

30:34and I was absolutely delighted to see this. And I followed them all back down. They go into the hole. Darwin saw the same thing when he was in the Brazilian rainforest. But no one knew for a long time what the ants were doing with these fragments of leaf. They thought, oh, they're just going to eat them in the comfort of their own home. But what they're doing is feeding them to a fungus garden, which they have down there, which they cultivate, which they weed, which they look after. They feed the fragments to the fungus. The fungus breaks down the cellulose that the ants don't like to have to try and digest.

31:03and then the ants eat the fungus. So they're farming the fungus. And then ants do all sorts of different things. Some other species farm animals. They keep them in herds. It might be aphids that they milk the aphids. They might take caterpillars of a species of butterfly. The caterpillar exudes a drop which the ant milks and then they tend to the caterpillar. So ants are incredible. If we didn't have them, many ecosystems would be very, very different. Well, let's leave it there then. Rowan Hooper, thank you so much for being with me today. Thanks, Ben.

32:02by SPD via Getty Images and Triple Scoop Music. I'm Benjamin Thompson. Thanks for listening.

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