From Microbes To Mammoths: How Life Transformed The Planet

ANNA ROTHSCHILD: This is Science Friday. I’m Anna Rothschild.

When we think about Earth, we’re inclined to think of a giant rock floating around in space, making laps around the Sun, a rock that just so happens to have critters and plants and people crawling around its surface. But a new book argues otherwise, that life doesn’t just exist on Earth, but that life is Earth. That Earth, in and of itself, is alive.

That idea might sound radical, and it is. There’s a shift happening in how we understand the Earth and what it’ll take to save it and ourselves from the future we’ve doomed it to. The book, Becoming Earth– How Our Planet Came to Life, takes readers on adventures all across the world, to learn how life has transformed the Earth.

Joining me is author Ferris Jabr, science writer based in Portland, Oregon. Welcome to Science Friday.

FERRIS JABR: Thank you. Thank you so much for having me. It’s great to be here.

ANNA ROTHSCHILD: I’m delighted to be chatting with you.

FERRIS JABR: Likewise.

ANNA ROTHSCHILD: So, Ferris, what do you mean when you say that Earth is alive?

FERRIS JABR: So the fundamental concept of a living world or a living planet is really ancient. We find this in mythologies and religions, going way back in time. But within the history of Western science, this concept of a living planet has been rather controversial for a long time. And it was really popularized by the Gaia hypothesis introduced in the 1960s and ’70s.

In the course of writing this book, I’ve come to see life, not as something that simply exists on the surface of the planet, but rather as a physical extension of the planet. And I think that what we call life and the larger planetary environment, together form a single, highly interconnected living system. So I’ve come to see all the organisms on the planet, plus the planet itself, as the largest known living system, the largest living entity that we know of.

ANNA ROTHSCHILD: How did you arrive at this idea, that Earth came to life?

FERRIS JABR: For me, it began at least 10 years ago when I learned this incredible fact about our planet’s largest forest, the Amazon rainforest, which is that the Amazon does not simply receive the rain for which it’s named. It actually generates about half of the rain that falls on its canopy each year. And the way this happens is truly astonishing because the Amazon is pulling huge volumes of water from the soil, releasing that water to the atmosphere. And, at the same time, it is throwing off all of these tiny biological particles, like pollen grains and microbes and fungal spores and even bits and pieces of leaves and insect shells.

And it’s the combination of all of that water in the atmosphere, released by the forest, and all these tiny living particles on which the water can condense, that dramatically accelerates the water cycle and the formation of clouds. That’s a huge part of what makes it so rainy in a rain forest. And this– learning that the Amazon did this, that the Amazon basically made its own weather and sustained itself to an extent by making its own rain– started to dramatically change the way I thought about the relationship between life and Earth. I’d always been told that life is subject to its environment, not the other way around. And that’s been the predominant thinking in Western science for a long time. The environment shapes life.

And even when the field of ecology began to recognize that sometimes life changes its environment as well, it was typically focused on pretty small-scale changes, like a beaver constructing a dam or some worms churning a patch of soil, not really taking seriously the idea that life could change something the size of a continent or an ocean or the planet. But when I learned about the Amazon, which spans an entire continent and changes weather throughout South America and even influences weather on other continents, I started to really question that conventional wisdom. And I started to look for other examples of life dramatically transforming its environment.

And I quickly found that the Amazon is just one example of this phenomenon. That, in fact, microbes, plants, fungi, and animals have radically altered the planet throughout the past at least 3.5 billion years. And they are responsible for many of the defining features of the planet. So when you start to see life that tightly interconnected with the planet’s fundamental geology and structure and chemistry, it raises the question of whether the entire Earth system itself is alive in some meaningful sense?

ANNA ROTHSCHILD: Right. I mean, you’re not the first person to raise this question. You mentioned the Gaia hypothesis from the 1970s before. Can you explain what that is?

FERRIS JABR: Sure. So British chemist and engineer and inventor James Lovelock proposed the Gaia hypothesis in the 1960s, and then he published his first full-length book on it in 1979. His initial insight came when he was actually working for NASA, at JPL. And they had asked him to help them find ways of detecting life on other planets.

And he realized you may not even need to go to another planet to do that, that wherever life emerged, it would inevitably transform its home planet. It would change the chemical equilibrium of that planet and push it into a new state. For example, Earth would not have an oxygen-rich environment were it not for life continually putting oxygen into the environment in the first place.

And he eventually came to what he called the Gaia hypothesis, which proposes that together, life and Earth are this single, self-regulating living system and that Earth in many ways resembled its smaller constituent life forms. It had rhythms and a kind of metabolism and a physiology that looked a lot what actual organisms were doing. And so he wanted to formally draw these comparisons.

Initially, Lovelock said that life was kind of working together to deliberately make the planet as habitable as possible. And that was one of the things that got him in trouble in the beginning and that he later retracted because he was giving life a bit too much agency, too much purpose. Over time, he and an American biologist named Lynn Margulis refined and developed the Gaia hypothesis together. Over time, they came to see it more as an emergent phenomenon, that this system they called Gaia, this living entity, emerged from these planetary-scale interactions between organisms and the ecosystems they were embedded in and the ways that they changed each other through geological time.

ANNA ROTHSCHILD: Let’s dive into an example, just to make this relationship really clear. If you had to pick one– this might be like picking between your children or something– what’s the most profound way that you think life has transformed the planet?

FERRIS JABR: I always come back to the long oxygenation of the planet as perhaps the single most profound change. So this began roughly 2.5 billion years ago, when these ocean microbes, called cyanobacteria, evolved oxygenic photosynthesis for the first time. So they were doing the kind of photosynthesis we are most familiar with now, where they are taking in sunlight and water and they are putting out oxygen as a byproduct. And in doing so, they started to suffuse the ocean and the atmosphere with oxygen, whereas before it essentially contained no free oxygen whatsoever.

And so slowly, over time, cyanobacteria, and then later algae and then much later land plants, they collectively transformed the atmosphere and the entire chemistry of the planet. Because once you shift the atmosphere to an oxygen-rich state, you’ve changed the chemistry of everything else that happens on Earth. So, originally, if we go back more than 3 billion years, Earth probably had this hazy orange sky, that was full of methane and carbon dioxide and was smoggy. When life started to oxygenate the atmosphere, it shifted the color of the sky to the blue part of the spectrum by changing the chemical composition of the air. So life is really why we have a blue sky in the first place.

And then having a high-oxygen environment and land plants, something that could burn, that made fire possible for the first time, maybe somewhere between 500 to 400 million years ago, whereas before fire was literally not possible because if you don’t have oxygen and combustible matter, you cannot have wildfire. And then we have something like 6,000 unique mineral species on Earth, which is vastly more than any other planetary body we’ve ever discovered, including the Moon and Mercury and Mars and all of our sibling planets. And most of those can only exist in a high-oxygen environment. So the mineral diversity of Earth that defines our planet is also largely because of life.

ANNA ROTHSCHILD: So you’re basically saying that bacteria farts changed the world.

[LAUGH]

FERRIS JABR: Absolutely. And I think we have to give microbes and their exhalations and various byproducts a lot of credit because they are the earliest, the most ancient, the smallest, the most fundamental form of life on this planet. And they really created many of the most profound changes, over billions of years, before any multicellular creatures even existed.

ANNA ROTHSCHILD: Right, right. I want to get into some more examples, because you really talk about some mind-blowing ways that life has profoundly altered Earth history. So one of the things you write about in your book is your trip to Siberia, to a place called Pleistocene Park, which is kind of giving Jurassic Park vibes a little bit. So what’s going on in Pleistocene Park?

FERRIS JABR: Pleistocene Park is a truly fascinating and daring experiment in the far Arctic, in Siberia, run by the Zimovs, Sergey and Nikita Zimov, a father and son scientific team, and their families. And they have this theory that large megafauna in the Pleistocene, things like mammoths and mastodons and bison, these large grazing animals, co-evolved with the grasslands that existed at the time. And so the grazers and the grasses maintained and sustained each other.

These large animals would trample the trees and shrubs that would otherwise compete with grass, and the grass would provide these grazers with this rapidly regenerating vegetation that they could continually graze on. But it went further than that in their estimation, because, together, the grasses and the grazers, according to their theory, were helping to keep the permafrost frozen.

So, for example, the grazers, just by being so large and by walking through these grasslands, were stripping away these insulating layers of snow, which allowed these frigid temperatures to penetrate deeper and keep that permafrost frozen. And grasses, just by virtue of being lighter, paler in color than trees, reflect more light and heat back to space. So they’re also keeping the land cooler. And so their idea is to bring back large grazing animals to Siberia, to recreate some version of these ancient Pleistocene grasslands, and thereby counteract the thawing of permafrost to some extent.

ANNA ROTHSCHILD: I mean, that was one of the most counterintuitive things in your book to me, the fact that actually by removing snow, by using their big feet to remove snow from the ground, it could keep the Earth cooler by freezing that ground beneath. I don’t know why, just it never occurred to me that by removing snow you could have a cooling effect. But it makes sense.

FERRIS JABR: Yeah, I know. I know exactly what you mean because sometimes we get these heavy snowfalls here in Portland, Oregon. And my first thought is to worry about our poor plants. But, actually, they’re probably being insulated. If the snow is actually covering them in the right way, that’s actually an insulating layer. And it’s when you remove that layer and they’re exposed to just the chill air itself, that they can actually get more damage– frost damage and ice damage.

ANNA ROTHSCHILD: In another of your many field trips in this book– which I have to say, I’m so jealous. You got to go to such incredible places to report this story. You travel deep underground and you look into microbes that actually breathe rock. I’m sorry. Tell us about that. What does that even mean?

FERRIS JABR: Yeah, that is truly bizarre. So I descended close to a mile beneath the surface of the planet, in this former gold mine in South Dakota that’s been converted into a scientific laboratory and a place for exploration. Most of the scientists there are actually physicists conducting these experiments, that have to be shielded from cosmic rays. But I went with a team of biologists, specifically geomicrobiologists.

They hunt for these really weird and fascinating microbes that live in the deep crust of our planet, miles beneath the surface. And they’re very different from most of the surface microbes that we know. They seem to be able to live for a really long time, potentially millions of years. They often have very slow metabolisms.

And some of them breathe rock, or metal, instead of oxygen. Breathing, or, I guess what’s more scientifically known as respiration, it’s all about moving electrons around in order to be able to do certain kinds of cellular work. And we use oxygen as our final dumping ground for these electrons. It’s an amazing electron acceptor. It’s so readily reacts with other elements.

But what if you live somewhere, where there isn’t a lot of oxygen or there’s no oxygen available? Well, you have to turn to other elements, other chemicals, that are also capable of accepting electrons. So rock and metal are alternatives. And they’ll work in a pinch. They’re not as efficient or as great as oxygen, but they can work.

So there are microbes that have learned to do this. Some of them will chew rock and metal and bring it into their cells. And others will actually create these external electrical conduits with the rock or metal that surrounds them. And they can pass electrons off to their rocky or metallic surroundings that way.

ANNA ROTHSCHILD: OK, so because these little microbes don’t have oxygen, they move electrons around using other elements– I mean, just bananas. So Ferris, what effect do these tiny organisms have on Earth’s crust?

FERRIS JABR: So in addition to inhabiting the deep crust and living in these pores that are filled with water, they are continually engaged in this alchemy of Earth. They’re converting minerals from one state to another. They’re taking minerals into their cells and changing them and putting out new byproducts. Some microbes will collect flakes of metal around them, that attract more and more metal flakes, that eventually turn into an ore of gold or silver or some other precious metal. And it is thought– it’s not definitive– but there is this theory that maybe some of these microbes were really important for the formation of the continents.

So the continental crust is made of granite, which, as far as we know, is only abundant on our planet. We’ve never found it in a significant amount anywhere else that we’ve looked in the cosmos. And granite is less dense than basalt, so it will float on top of the basalt. And that’s really where the continents came from in the first place, is that it was this less dense layer of granite that floated over the oceanic basalt, and therefore rose above sea level over time.

And microbes, by inhabiting and dissolving the ancient crust, likely made that crust more hydrated, basically. They brought these wet clay byproducts into the crust. They basically lubricated it and accelerated this process of subduction that was fundamental for the creation, the formation of those initial layers of granite in continental crust.

So microbes may have, to some extent, laid the groundwork for all other terrestrial life. And some models, some scientific models and computer models, suggest if it wasn’t for life, we may have had an Earth that’s just pockmarked by islands here and there or had very small continents, but really not the massive landmasses that we have now.

ANNA ROTHSCHILD: Ah, that is so fascinating. I mean, microbes basically creating the continents in some way. It’s just– it’s not something that you would imagine. But it makes sense when you read about it in the book. It’s so incredible.

FERRIS JABR: It really flips things around because we’re so used to thinking of life inhabiting what is already there, not creating what it needs to live or creating something that future generations of life could use. But what we’re learning more and more is that’s exactly what life does, is that life doesn’t just use what it finds. It makes new things that haven’t existed before. It profoundly transforms the planet. And then subsequent generations, subsequent waves of evolving life, take advantage of what life before them made.

ANNA ROTHSCHILD: This is Science Friday. I’m Anna Rothschild. I’m talking with science writer Ferris Jabr about his new book, Becoming Earth, all about how life transformed the planet. Ferris, what’s something you learned that broke your brain while you were writing this book?

FERRIS JABR: When I learned about the connection between plankton and giant pieces of the Earth’s bones and rocks and structure, that really blew my mind. So if you take a small piece of the White Cliffs of Dover in the UK, a small piece of the chalk or limestone that makes up these massive cliffs, and you look at it under a really powerful microscope, you will see these little, tiny bone-like structures, these little pegs, that are packed together just like the stones in a stone archway.

And that’s because what you’re looking at are the degraded remains of the exoskeletons of ancient single-celled plankton that lived in the ocean around 65 million years ago. And they encased themselves in these intricate, lacy skeletons of limestone. And when they died, they sank to the sea floor. And their skeletons collected in these deep seafloor sediments, and eventually petrified. They turned to stone over time.

And then, through changing sea levels, sometimes these petrified sediments are exposed. And that is exactly what the White Cliffs of Dover is. It’s a massive collection of tiny single-celled fossils. And, in fact, it turns out that most limestone formations on the planet are made of the remains of ancient plankton and other ocean creatures that build chalky shells or skeletons for themselves, which means that all of the structures we have built with limestone and chalk, like the Washington Monument or the Colosseum or the Pyramids of Giza, are themselves made of plankton and these other ancient ocean creatures.

So that was truly mind-blowing for me. And I think that speaks so well to the reciprocity of life and Earth, of geology and biology, how life is literally becoming rock and then becoming life again. These incredible dusts blow over from the Sahara to the Amazon. And they fertilize the Amazon rainforest with a lot of the nutrients that the forest needs.

That dust is also essentially ancient plankton. It’s coming from these ancient lakes in Africa, these ancient lake beds, where all of these ancient fossilized plankton skeletons are accumulated. And then they’re blowing across the ocean onto another continent and fertilizing a thriving forest that has endured for millions of years.

ANNA ROTHSCHILD: Ah, just incredible. You know, Ferris, let’s get existential for a moment. This book really makes you question what it means to be alive. Do scientists have a standard definition of life?

FERRIS JABR: They don’t. And that is one of the things that fascinates me the most about life, is that clearly this has been an obsession for science for millennia. And yet, to this day, we do not have a precise consensus definition of life.

If you open a textbook, you will see long lists of criteria of qualities that supposedly distinguish the animate from the inanimate, but not a precise definition, and certainly not some fundamental, beautiful equation that explains the phenomenon we call life. And so scientists are continually debating and reconsidering how best to define life. It very much remains an open question.

ANNA ROTHSCHILD: When the Gaia hypothesis first came out in the ’70s, it was panned as an idea by many scientists. I’m wondering, is this book part of a greater wave of rethinking the Gaia hypothesis and rethinking what Earth itself is?

FERRIS JABR: I think so. I think we are seeing the start of a movement right now, that is really going to bring this idea of the co-evolution of Earth and life, and of thinking of Earth as a living planet, to the forefront. And I think that’s in part because of how relevant this is to what our planet is going through right now.

But I know of a lot of writers and scientists who are thinking about these ideas, these interrelated ideas of Earth and life changing each other and what it means for a system as large as the Amazon or, indeed, the entire planet to be alive. And as you were saying, a lot of scientists, in particular in the life sciences, harshly criticized and ridiculed Gaia when it first emerged. And I think that was in large part because there was this conflation between saying Earth was alive and saying Earth was an organism.

Lynn Margulis, in particular, should get a lot of credit for clarifying, over time, that to say Earth is alive does not mean you are saying Earth is an organism. I’ve come to see life as something that happens at multiple scales. Like a cell is not an organism, but a cell is alive. Everybody agrees about that. So why can’t we extend that to things that are larger than organisms? That’s where the debate really begins, is below the level of the cell, with things like viruses, and then above the level of the organism, with things like ecosystems and planets.

But I see all of these things now as systems. They’re networks of interrelated components, that are partly animate and partly inanimate. And I think what we call life can emerge at any of those levels or scales. And I think that is– that’s part of the realization we are coming to, is that we need to broaden our concept of what life is, of what constitutes a living system.

ANNA ROTHSCHILD: I mean, even the human body is a system, if you really think about it. Like, we contain many parts that are inorganic. We contain iron and other minerals and we require those to live. And we also require other microbes to live. Our microbiome– without our microbiome, we simply could not be alive. So even within ourselves, we are complex. We contain organic and inorganic parts.

FERRIS JABR: Yeah, could not have said it better myself. And I think there’s this beautiful analogy, between, say, the human body, a tree and Planet Earth, where each of those is a complex system that is made of both the animate and inanimate. And, actually, by mass or volume, each of those is mostly inanimate.

The human body, by weight, is mostly water. We have skeletons that are largely rock or mineral, if you want to think of them that way. A tree is mostly dead wood, dead tissue, that’s sort of laced and ringed with living cells. Earth is mostly rock and water and air, but it has this incredible flowering skin of life.

And, in each case, that minority of living tissue, of living things, sustains this larger living system or living entity. So Earth is not unusual in that sense. Like, we and Earth are very much analogous in that way.

ANNA ROTHSCHILD: Did writing this book change your idea of what needs to happen to keep our future from– well, being engulfed in literal flames?

FERRIS JABR: Yeah. I mean, first of all, it changed the way that I see myself in relation to the planet pretty fundamentally because I honestly do not think of myself as just another creature– as only just another creature on the skin of this planet anymore. I now see myself as literally continuous with the matter of the planet, as literally an extension, a physical extension, of the planet. And I’ve come to see all life that way. I think that’s something we sometimes feel or intuit about organisms, like plants, that are literally rooted to the Earth and literally grow out of it.

But I think that’s true for all of us, because life necessarily emerged from the matter of Earth. It was only the matter of the planet that was available to become life, to become animated. And then, I think, thinking of the Earth as a true living entity, not accepting that as a scientific reality, not just some sort of woo-woo mystical thought or a nice turn of phrase, but like a literal scientific reality, is also profoundly distinct from thinking of ourselves as merely inhabiting the planet or simply being passengers on this so-called Spaceship Earth.

If we are literally Earth, if we are literally extensions of Earth, then the urgency of what we have to do right now, and the moral obligation of what we have to do right now, is heightened all the more. And I think, in parallel, the kind of science we’ve been talking about, Earth system science, is such a clarifying guide for how to best respond to the current climate crisis because it really– it forces you to reckon with what we are doing in the most truest, most material way. That we can’t just think of it as pumping our cars full of gas and releasing bad pollution to the atmosphere– and we’re bad humans for doing that. No.

Like, what are we actually doing? We’re going into the bowels of the planet, unearthing ancient life, burning it, releasing all of that carbon to the atmosphere and completely throwing the planet’s long-evolved rhythms out of balance. For me, that’s a much clearer, more profound and more compelling way to think about what is happening to our planet right now.

ANNA ROTHSCHILD: Ferris, thank you so much for joining me today. This was such a pleasure.

FERRIS JABR: Likewise. This was so much fun. Thank you for having me.

ANNA ROTHSCHILD: Ferris Jabr is a science writer and author of Becoming Earth. Read an excerpt from the book at sciencefriday.com/earth.

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