14 Luke Steller: Primordial soup

[00:00:09] I'm Catherine Polcz and this is Plant Kingdom. I'm recording in Sydney on the lands of the Gadigal people of the Eora Nation and pay respect to their elders past, present, and future.

[00:00:19] Plant Kingdom is a conversation series about the sublime in nature and environment, featuring scientists, artists, researchers, and writers.

[00:00:27] We release two conversations each month and hear from people who have an intimacy with nature. We discuss their works, stories, and reflections from the field.

[00:00:36] Today's conversation is with astrobiologist and science communicator Dr. Luke Steller.

[00:00:42] In our conversation, we weigh deep into the primordial soup and discuss the enigma of Earth's first life.

[00:00:50] We ask what were the conditions required, what could life have looked like 3 billion years ago, and what life might look like elsewhere in our universe.

[00:00:59] Here's our conversation.

[00:01:11] Well, thank you so much, Luke, for chatting today.

[00:01:15] I'm really looking forward to our conversation.

[00:01:19] And I guess to just start us off, your research is in a really interesting field called astrobiology.

[00:01:28] Astrobiology, what even is astrobiology? What does that mean?

[00:01:34] Yeah. Thank you so much for having me.

[00:01:36] It's a really weird question.

[00:01:38] And when I tell people, you know, I study astrobiology, a lot of people think I'm joking, but I think it's like a made up word.

[00:01:45] Because when you put it together, it kind of doesn't make sense.

[00:01:48] You know, astro is space.

[00:01:49] Biology is life.

[00:01:51] So it's really the study of life in space, which, you know, as far as we know, if you don't believe many of the movies out there, there's not much of it.

[00:01:58] So it's a tough one to get your head around.

[00:02:00] But it really is the study of the probability of finding life out there in the universe.

[00:02:06] So it's this beautiful mix of looking at how did life form on Earth and how do we actually understand the building blocks needed for life to come together in really primitive planets.

[00:02:17] And then how would you find that life elsewhere?

[00:02:20] And that can go from trying to find physical fossils on places like Mars to detecting techno signatures.

[00:02:27] So we're talking about radio waves or like, you know, stray TV signal coming off distant solar systems that we can intercept.

[00:02:34] So it's this huge array of little pockets of science that are coming together trying to answer that question, which really is, are we alone in the universe?

[00:02:46] And I think that it also is about life on Earth is unexpected, but something that I just keeps coming up in so many conversations that, of course, you know, Earth is in space.

[00:02:57] And also like combating the idea that space is dead, right?

[00:03:02] Or space is other and outer.

[00:03:04] I think it's a really interesting field and playing with all of those kind of paradigms we have about how we think about space.

[00:03:11] Yeah, totally.

[00:03:13] And I think it's that the idea that space is dead or that space is nothing or has no kind of intrinsic value.

[00:03:21] Before it used to be a very like conceptual idea, you know, like the, you know, big unknown out there.

[00:03:26] But I think as we, the human race have more capabilities, individuals can send spaceships to Mars in the next 10 years.

[00:03:35] You know, there will be asteroid mining and all kinds of stuff.

[00:03:38] And the ethics of like, what is the intrinsic value of space?

[00:03:42] Like space, if it's the way that we view it, if it is lifeless in some capacity, what does that mean for just going and harvesting resources or messing up the conservation value of a lot of places on Mars?

[00:03:53] And it really, this once philosophical kind of concept is actually a really practical question that we have to start asking ourselves.

[00:04:02] Yeah, it's becoming much more part of our life on Earth too and into the future.

[00:04:08] And how do we, yeah, conserve space?

[00:04:10] Space environmentalism is my obsessive pet topic.

[00:04:13] It's just the ideas that it brings forward and how it lets you look at Earth differently too, where just our values are just so bare when you think of them in space.

[00:04:22] It's kind of a sideways door into thinking about Earth too.

[00:04:27] Yeah, and just the kind of time traveling aspect of astrobiology too is so interesting.

[00:04:32] Like before there was life on Earth, there was geology, physics, beginnings of chemistry.

[00:04:39] And those are all at play throughout the universe.

[00:04:44] Yeah.

[00:04:46] Yeah, yeah.

[00:04:47] And really, when you start kind of, yeah, breaking down life or, you know, the process of life coming together in some way, you really just understand that biology, it just is chemistry and geology and physics.

[00:05:01] The fundamental forces, you know, those high school subjects that you study are really driving the incredible creativity and beautiful complexity that is life as we know it.

[00:05:13] So, yeah, it's a really, really trippy thing to get your head around a lot of the time.

[00:05:17] And the interplay of them before they were all broken up into different textbooks.

[00:05:23] They were all, it's not the reality of how they interact, is it?

[00:05:26] Yeah, that's a very human thing to want.

[00:05:28] As you said, like, there's space in this idea of like, that's out there and we're here or, you know, geology, you only study that, but then you can't study this.

[00:05:37] And I think that was the beauty of the academic pursuit of astrobiology was it's a field of science that's defined by the question, not so much as the topic.

[00:05:48] Where in geology or in chemistry, it's like, if you're working with molecules of this size, that goes to chemistry.

[00:05:54] But as soon as, you know, you can start to go in it, that's geology.

[00:05:59] Whereas astrobiology, it's like, well, we've got this big question.

[00:06:02] We're going to have to throw everything at it, you know, when you're talking to philosophers about, you know, the basic principles of life and geochemists and astrophysicists and everyone's coming together in this kind of equal playing field of like, hey, we just got to figure this thing out.

[00:06:16] And it doesn't matter how we get there.

[00:06:19] And it started for you, I believe, in a pretty special place in the Pilbara.

[00:06:25] Is that, is that right?

[00:06:26] Where did this research and interest begin?

[00:06:30] It all began.

[00:06:31] And I always caveat this story that I wasn't a space kid growing up.

[00:06:36] I think a lot of people, wow, you did astrobiology and you're partnering with NASA on projects and all this kind of stuff.

[00:06:42] You must have loved space.

[00:06:44] Yeah, it wasn't really a thing.

[00:06:45] I think I grew up definitely, my dad's an ecologist and lots of bushwalking and hiking and the natural world.

[00:06:52] And my dad specialised in, you know, native grass identification.

[00:06:55] Childhood was just spent going through bushwalks of fields that look exactly the same to anyone else.

[00:07:01] Yeah, very minutiae of the details of the landscape.

[00:07:04] So that was my childhood and my real passion.

[00:07:06] Yeah, it was really in, I guess, second year uni.

[00:07:09] I was studying environmental science.

[00:07:11] I was really interested in the natural world.

[00:07:13] And there was this amazing professor at University of New South Wales where I was studying called Martin Van Cranendong.

[00:07:20] And he would go to the Pilbara, which is, you know, remote, far western Australia, a numble country in the middle of nowhere.

[00:07:28] And it's just these jagged hills and spin effects and kangaroos and camels and a really kind of beautiful expanse.

[00:07:37] And he would go over there studying these fossils.

[00:07:39] And to be honest, I didn't really care much about the fossils.

[00:07:43] But the idea of I could volunteer with him and go out into the Pilbara and spend a month driving a beaten up ute around these incredible ancient landscapes.

[00:07:52] That just really appealed to me.

[00:07:54] So, yeah, basically he was looking for a driver.

[00:07:56] He had a master's student who was doing some brilliant work out there studying the formation of the ancient, they call it a caldera.

[00:08:05] It's like this craton.

[00:08:06] It's like an ancient volcano that lifted up that whole area and put all these cracks through the landscape.

[00:08:12] And these cracks filled up with silica, dissolved water with rocks dissolved in them, kind of filled up all these cracks deep on the ground and then solidified.

[00:08:21] And then as all the landscape, all the rocks around it got washed away, you got left with these kind of, they honestly look and feel like brick walls that are like two meters tall running through the landscape.

[00:08:34] And they're kind of crossing over each other.

[00:08:36] You have to climb over them to get anywhere.

[00:08:38] And this amazing master's student was mapping out the structure of these cracks and what that could tell you about the way that landscape was lifted up in this ancient volcano.

[00:08:49] Brilliant research, really lovely guy, but didn't have an Australian driver's license.

[00:08:53] So it was like, hey, if you want an all expenses paid for trip driving around some of the most remote roads in Australia.

[00:08:59] I don't know if I should say this because my supervisor might not be happy with me, but I literally just caught a hammock and I would perch up on top of one of the hills and I would just read all these books.

[00:09:10] So I looked at the landscape and throw rocks at other rocks and whittle sticks.

[00:09:15] And I just had this really restful and beautiful month out in the Pilbara, just being really present while I watched this master's student kind of do these 10 kilometer transects through the bush, trying to like measure all of these rocks.

[00:09:27] So I had a really beautiful time to really settle into that landscape before I had to study it.

[00:09:32] You know, I wasn't able to analyze it or extract information.

[00:09:35] I was just there to be present and to make sure, yeah, this student had a set of wills.

[00:09:39] So, yeah, that was my introduction into that landscape and into the geology out there and all of the stories that geology could tell.

[00:09:46] And from the fireside campsites and chatting with all the other researchers there, I started to appreciate that, you know, these rocks and these, you know, pretty, from my perspective, you know, mundane fossils, when you first see them actually can tell the story of every living entity on our planet,

[00:10:04] which really piqued my interest after a while.

[00:10:07] Yeah, just the story of every living.

[00:10:10] Yeah, yeah.

[00:10:10] That's pretty up, yeah.

[00:10:14] So beautiful.

[00:10:15] And how, why do those rocks tell that story?

[00:10:18] How old, how old is that country?

[00:10:21] How old is the land?

[00:10:24] Yeah, it's amazing.

[00:10:26] You know, Australia as a continent, we've got some old stuff.

[00:10:30] We're really, we're ticking a lot of boxes.

[00:10:32] Out in that region, we have the oldest mineral grains on the planet.

[00:10:37] They call them the Jack Hill zircons.

[00:10:39] And this is like the oldest surviving grain, like little crystal grain on the planet.

[00:10:44] And that's like 4 billion years old.

[00:10:47] So the Earth formed at 4 and a half billion years.

[00:10:50] This is like Earth formed molten solar system.

[00:10:53] There was this cataclysmic crashes where our moon very likely formed from another planet hitting the Earth,

[00:11:02] showering off all of this crap that kind of ended up being the moon.

[00:11:06] Like it was this incredibly, they call it the Hadean as a geological record.

[00:11:10] It's like Hades, you know, like everything was just blowing up and molten and just crazy.

[00:11:14] So that was like for the first 500 million years, the first half a billion years from 4.5 to 4, which is absolute chaos.

[00:11:24] And then very quickly, the Earth started to cool down.

[00:11:26] And you got these little, you know, it was cool enough for mineral grains to start actually solidifying and precipitating out.

[00:11:33] And then that's the area that we're studying out there.

[00:11:37] That's how old these landscapes are.

[00:11:39] And then the specific fossils I was studying, they're at 3.5 billion years.

[00:11:45] So that's like a billion years after the chaos of the formation of the Earth, but still so young.

[00:11:53] And it's incredible to go out there and you can literally see ripple marks.

[00:11:57] So you can see places where water's been flowing that are 3.5 billion years old.

[00:12:03] It's amazing to be able to touch aspects of the landscape and be like water flowed here billions of years ago.

[00:12:09] And it's just, yeah, so that's the timeframe that we're looking at.

[00:12:13] And in that landscape, there are these fossils called stromatolites.

[00:12:17] These fossils, firstly, the organisms are incredible.

[00:12:20] And they're the same structured organisms that we have in modern day Shark Bay.

[00:12:25] So you might have heard of Shark Bay and there's these living stromatolites.

[00:12:29] And they just look like slimy kind of pebbles that are scattered throughout a tidal kind of flat.

[00:12:36] But these pebbles are actually layers and layers of microbes.

[00:12:40] So they're little, you know, microorganisms that kind of cover the top layer of a tiny grain.

[00:12:46] And then a little bit of sediment will sort of settle down in the water and cover it up.

[00:12:50] And the microbe doesn't want to be covered.

[00:12:52] So it'll grow another layer.

[00:12:53] And it's kind of this race against the tritus and this race against, you know, little bits of dirt getting put on top of it.

[00:13:01] And because of that, it forms these beautiful layered shrouded rocks that kind of build up against the rest of the geology.

[00:13:08] Everything else is getting washed away and kind of forming these flat surfaces.

[00:13:12] But they build these kind of curved pebbles that kind of grow up out of the water.

[00:13:17] And amazingly, we can see those similar structures three and a half billion years ago.

[00:13:24] So when we're looking for these landscapes, you know, you can see ripples.

[00:13:28] You can see places where there are little tidal flats.

[00:13:30] And then there's actually these microbe colonies, those little organisms growing up out of that.

[00:13:36] And we can see them and you can put your finger on them and say that is one of the oldest evidence of life in the entire world.

[00:13:44] That's as far back as you go.

[00:13:45] You can touch it and say, this is it.

[00:13:47] And that's really special.

[00:13:49] And from that, we can really understand what environments the early earth had and how those might have formed.

[00:13:55] So we can kind of, as a point on that map of time, we can go backwards and say, what led up to that point where you had these microorganisms growing?

[00:14:06] And then we can also look forward, like, how did you go from that to where we are today?

[00:14:11] What factors had to come into play to create the entire living world that we know and love?

[00:14:19] It's just so fascinating and so beautiful.

[00:14:23] And even just thinking of, you know, the Shark Bay stromatolites are descendants from those really billion-year-old stromatolites, right?

[00:14:36] It's fun to put your finger on that, like, rock and be like, this is everyone's great, great, great, great, great, great, a billion times great grandmother, you know?

[00:14:44] And, like, all life came out of that.

[00:14:45] But really, that's really hard and vague to say.

[00:14:49] We know that they were very old.

[00:14:50] We don't know when they branched off that tree of life, which makes it interesting.

[00:14:55] But we do know that there was a bottleneck in the tree of life.

[00:14:59] There was a single stem, that trunk that everything came out of.

[00:15:03] And we know that there was one organism, one genetically individualized organism that you can put your finger on and say, that's everyone's grandmother.

[00:15:14] And from that bottleneck, from that little narrow point, everything branched out of.

[00:15:19] And there's a really cute name for it.

[00:15:20] They call it LUCA, which stands for the last universal common ancestor.

[00:15:25] So that's the last time that all of us were all related.

[00:15:28] And then from that, yeah, all life on earth kind of just branched out from there.

[00:15:35] So amazing.

[00:15:36] And LUCA is, you know, who we're here to talk about today.

[00:15:41] And what was the particular focus of your research?

[00:15:46] Yeah, so my research is really studying the chemical and geological origins of life.

[00:15:54] So when you're thinking about how do you get to that LUCA, and really what we're trying to get to in the origin of life research is a individual chemical entity, which you could define as a cell that can replicate itself.

[00:16:07] You need something that can split or that can divide or that can replicate itself and make more of itself.

[00:16:13] And that can carry genetic information.

[00:16:15] So it can kind of have a semblance to its parents, but also that there's a bit of diversity.

[00:16:20] You know, you need a little bit of diversity in that genetic code.

[00:16:23] And from that, that's like the driving forces of evolution.

[00:16:27] So as soon as you can create something that can pass on information, that can divide, that can have your genetic diversity as well, it's all fair game from there.

[00:16:37] And then everything in life that we see now can be driven by those simple principles, the driving forces of evolution.

[00:16:44] So what I was looking at was how do you bring geology and chemistry together to create something like that?

[00:16:52] How do you create membranes that can create cell walls in environments where there's no cells?

[00:16:58] How do you create genetic material for the very first time when there's no parent template to copy off?

[00:17:05] What did the first aspects of that primordial soup that created life come from?

[00:17:11] But in reality, like the early earth would have been incredibly messy.

[00:17:16] And there would have been hundreds of different bubbling pools or little streams coming in together, lightning, heaps of different minerals mixing together.

[00:17:27] So we can't apply these very simple, clean, linear processes, dynamic, cyclic, you know, incredibly diverse processes.

[00:17:38] So how do we bring it into the lab?

[00:17:40] So it's kind of my job over the four year PhD to really understand how do we get our experiments in the lab to mimic the diversity and complexity of the early primordial earth.

[00:17:57] So fascinating.

[00:17:59] And I guess, yeah, when you're looking at the geology and the chemistry, like the rocks on earth would be different everywhere you are, right?

[00:18:06] The unique mixture of everything would be quite variable.

[00:18:10] Yeah.

[00:18:10] How long ago do scientists think the first life did evolve?

[00:18:17] Or do we even know?

[00:18:20] No, no, no.

[00:18:21] That's a really good question.

[00:18:22] I think we can kind of put upper and lower limits around it.

[00:18:26] We know just from geophysics and from the rock record that before, say, 4 billion years ago, like 3.9 billion years, liquid water would evaporate on the planet Earth.

[00:18:38] You wouldn't have really any pockets of anywhere near calm enough, safe enough for life to form.

[00:18:45] They talk about this thing they call the late heavy bombardment.

[00:18:49] And it was almost like the solar system when it was just before it was settling down.

[00:18:53] It's like, no, wait a minute.

[00:18:54] Let's just go crazy one last time.

[00:18:56] I mean, a kind of cataclysmic like asteroid belts forming and planets getting pushed through them.

[00:19:02] And yeah, and that was around, you know, 4 billion years ago.

[00:19:05] So the Earth, we're very confident, could very likely not have any life forming before 4 billion years.

[00:19:10] And we know that definitely at 3.5 and maybe at 3.7 billion years, we have these fossilized stromatolites.

[00:19:17] So we know in that kind of window, a few hundred million years, which isn't that long a time, life must have got going because you have evidence of life at the end of that whole process.

[00:19:27] So that's the kind of the window that we're working in.

[00:19:30] And I think you may have touched upon this already, but what makes something alive?

[00:19:38] Is there a definition of that?

[00:19:41] Like there's a few, I guess, traits or things that we're looking for.

[00:19:45] But yeah, what is alive in this era?

[00:19:50] No, yeah, that's the big question.

[00:19:52] And I think that's the beauty of studying this subject is that you're kind of, you know, you're doing a day-to-day mundane experiments in the lab or, you know, grinding up your rocks that you've collected and trying to extract element out of it for analysis.

[00:20:05] And it can feel a bit dry sometimes.

[00:20:09] You're driven by, you know, you go to a conference and you sit down with an evolutionary philosopher and you're sitting at a NASA roundtable and everyone wants to know what's the definition of life is.

[00:20:20] Because that's one of the biggest and hardest questions to answer in the field.

[00:20:24] So it really gets you going.

[00:20:26] So NASA's got a definition, which is kind of used, but has a lot of caveats and ifs and buts and that kind of stuff.

[00:20:32] And that definition is a, so it's a self-sustaining chemical system capable of Darwinian evolution.

[00:20:41] And you mentioned it.

[00:20:43] Tell me, what is the primordial soup?

[00:20:46] Remind us.

[00:20:47] Remind us.

[00:20:48] Yeah, this soup.

[00:20:49] Everyone loves this Campbell's primordial soup.

[00:20:51] No, and it's interesting.

[00:20:52] Even that's really contentious, debated.

[00:20:55] People have all these different ideas.

[00:20:56] Really?

[00:20:57] Yeah.

[00:20:58] Yeah, yeah.

[00:20:58] And I think that's the, because you're looking so far back, you know, you're basically trying to say what did the earth look like before there was a rock record?

[00:21:06] You know, before there's any chance of ever recording that, we're kind of extrapolating.

[00:21:11] And we're stretching back a bit and we're using a lot of really good data and we're looking at other environments and we're looking at what came in on asteroids and all that kind of stuff.

[00:21:20] But it is really hard, you know, and it is debated.

[00:21:22] But basically the primordial soup is the soup which life emerged out of.

[00:21:27] And that soup, you know, could be a little puddle in a hot spring.

[00:21:30] It could be in the ocean, but it would have been somewhere on planet earth.

[00:21:34] And so just to caveat all of this and feel free, we can jump into this more later, but we're making a lot of assumptions that life formed on earth in this discussion.

[00:21:43] And just as a quick little aside, could have not happened, you know, like life could have formed on Mars and somewhere else and got delivered.

[00:21:51] Like we know that there's a lot of exchange of material between earth and Mars where bits of Mars are knocked off all the time and scattered into space and have landed on earth.

[00:22:01] And we have Martian rocks already on earth from these events of them getting scattered into space and landing on earth as meteorites.

[00:22:09] So we know that simple organisms can survive tardigrades and all that kind of stuff can survive the vacuum of space and easy being deposited here.

[00:22:18] So whether on earth or somewhere else, that's my little caveat.

[00:22:21] But anyway, we know it would have been quite similar where you would have had the broth.

[00:22:24] You would have started with a liquid base because we know life needs a solvent to move molecules around in.

[00:22:31] Water is a really good solvent.

[00:22:32] We think it probably was very likely water.

[00:22:34] Who knows?

[00:22:35] It could have been in a methane lake somewhere on Titan or somewhere else, you know, but that starts getting more and more unlikely.

[00:22:43] But yeah, so I guess if you look at a probability and like the likelihood would have been water.

[00:22:47] And then you would have had a lot of carbon.

[00:22:49] And that carbon would have been a mixture of carbon that's being cooked up and processed on earth.

[00:22:54] And you would have had carbon molecules deep underground that pressure, temperature, cooked up and started making oils and little alkanes and little kind of chemical complex molecules that are coming up to the surface and ending up in your primordial soup.

[00:23:10] That carbon would have also been delivered from space.

[00:23:12] So we know there's a lot of carbon in space.

[00:23:14] Carbon is a really common element and it's just floating around in space.

[00:23:19] And carbon does this really weird thing where if you cool carbon down and you trap it in ice, which is what a lot of carbon on asteroids and that kind of stuff is like.

[00:23:27] And you bombard it with UV radiation, which is, you know, blasting all through space.

[00:23:32] You actually start getting some really complex carbon molecules forming.

[00:23:37] In the depth of space where we know there was, you know, almost no chance of biological life doing it.

[00:23:44] We find, I think it's like 16 or 17 of the essential amino acids that we have in biology today out of the 20 that we have today, we can find in space.

[00:23:56] Yeah.

[00:23:57] And that's just from carbon getting cooked up and elements and electromagnetic radiation smashing into it and making bonds and kind of making these really complex chemical structures.

[00:24:09] And the soup, is the soup alive?

[00:24:14] The soup is the soup.

[00:24:17] Yeah.

[00:24:18] Yeah.

[00:24:18] The soup is the soup.

[00:24:19] The soup is not alive yet, but it's starting to have these processes.

[00:24:24] Maybe it's forming little membranes that can start to encapsulate molecules to form protocells where there's little bubbles that have more stuff inside of them than outside of them.

[00:24:35] And maybe that's where cells started evolving, you know?

[00:24:38] So there's aspects of that.

[00:24:41] Incredible.

[00:24:42] And even just thinking back about carbon, like all the carbon we have that's in our bodies, that's in plants, that we breathe out, that we burn from the bodies of dead organisms.

[00:24:51] It was here.

[00:24:54] It's part of, yeah.

[00:24:55] Yeah, yeah.

[00:24:56] It was here.

[00:24:56] It was all floating around.

[00:24:58] And I think that even though there was a lot of stuff delivered in that, you know, a lot of carbon molecules delivered in that early, early era of the earth, most of it was already here just in the formation of the planet.

[00:25:11] I think that's beautiful.

[00:25:12] We're almost like a giant terrarium, you know?

[00:25:15] Yeah, yeah.

[00:25:17] All the carbon and everything we need is just already here.

[00:25:19] We've just like swapped it around into a different pattern.

[00:25:22] And then look, we've got life and we've, you know, all kinds of things that you'd never think you could shake that snow globe well enough to make.

[00:25:29] But here we are.

[00:25:30] Yeah.

[00:25:32] Yeah.

[00:25:32] It's the, it's the cliche.

[00:25:34] It's the star stuff.

[00:25:36] All of these elements.

[00:25:37] Yeah.

[00:25:38] Yeah.

[00:25:38] And so the reaction happened somewhere on earth.

[00:25:43] That's probably, it has been consumed and looks totally different now.

[00:25:47] And then it's had to spread, I guess, over billions of years and evolve.

[00:25:53] Yeah.

[00:25:53] Totally.

[00:25:54] Yeah.

[00:25:55] It wouldn't have spread or evolved.

[00:25:56] But that evolution is a really slow process.

[00:26:00] And I think this is, I'm sure for a lot of, you know, yourself and others who study biology and you're looking really at a highlights reel of the earth.

[00:26:09] Because, you know, we're studying that time before life and it would have been really exciting.

[00:26:12] And the level of complexity would have been great to go from just a few carbon atoms to that single strumently light that we can see in the Pilbara at 3.5.

[00:26:20] But then really not much happened, honestly, until 0.5.

[00:26:25] So there's this like kind of like two and a half, three billion year stretch of just these little microbial mats and really primitive little kind of gooey structures just floating around.

[00:26:36] And then it wasn't until that kind of explosion half a billion years ago that everything, the way that we see life today.

[00:26:42] And this is a friend of mine and a collaborator, Eliza Cooper.

[00:26:47] She's an incredible contemporary dancer and creative, but also studied biology.

[00:26:53] And she made this beautiful, I guess, contemporary dance performance called Old Life, Dead Life.

[00:26:59] And it's basically this like how would you dance out the biological history of the earth?

[00:27:05] And it's really creative, explosive movements that were the crampion explosion, all this kind of stuff.

[00:27:11] But at the same time, she just had for like what felt like ages, just like people moving really, really, really slowly across the stage.

[00:27:21] And it's kind of this idea that biology and the history of biology wasn't as huge highlights real.

[00:27:25] It was really just like billions of years of just gunk floating around, you know.

[00:27:29] And that's where we're actually living in the most exciting part of the entire world because there was a lot of waiting around for something to happen, you know.

[00:27:39] And so many dead ends too, right?

[00:27:42] So many forms that don't have descendants.

[00:27:46] It's the winners write the history, right?

[00:27:51] I've never heard it said in that context.

[00:27:54] It's really true.

[00:27:56] Yeah.

[00:27:57] And I think that's funny that the idea of the winners writing the history is a concept that, not set in that way, but it's that anthropogenic bias that we have in astrobiology.

[00:28:08] The same way that we as humans or we as, you know, earthbound life sit around and we think that all life has to look like us and that life has to be based on chemistry or life has to be based on water.

[00:28:21] And the fact that because we're the winning genetic lottery that has come out of the primordial soup on earth, we have no idea of life has to look remotely even like us.

[00:28:32] We're looking for it in other planets.

[00:28:33] And that's this kind of, you have to have this humility when you're thinking about going to really alien worlds, you know, places like Titan or these moons around Jupiter and Saturn that have methane lakes because it's so cold or like deep kilometers of ice and then these big hydrofemyl vents underneath them.

[00:28:51] The chemistry is so alien to think that we would have even DNA or ribos or, you know, amino acids is just totally, it's egotistic, you know, to think that life should look like ours.

[00:29:03] Yeah.

[00:29:04] So interesting.

[00:29:06] Yeah.

[00:29:08] And you mentioned just hot springs in brief too.

[00:29:11] You've done a lot of work in around hot springs.

[00:29:14] You just talk about that a little bit.

[00:29:16] What do we, what do we hope to learn from hot springs or why are they important in this research?

[00:29:22] Yeah.

[00:29:23] Yeah.

[00:29:23] So I, um, when I first did my chauffeur trip around the Pilbara, I came in at a really amazing time in the field because literally that year there was an amazing master's student at the time.

[00:29:36] She's now got a PhD and doing incredible stuff.

[00:29:38] Her name's Dr. Tara Jokic.

[00:29:39] And then, as I said, my professor, Martin Jack Cranendong, they discovered a rock that was embedded right next to one of these gematilites.

[00:29:48] And they took it, you know, back to the lab and analyzed and spent all this time looking at it.

[00:29:52] And they found that that rock could have only formed in a surficial hot spring, kind of like Yellowstone or Rotorua.

[00:30:00] So when they used to think that these gematilites were growing, kind of like modern day gematilites in a really nice, quiet pool.

[00:30:07] Oh, sorry.

[00:30:08] Like a, you know, a little tidal pool on the side of the ocean.

[00:30:11] Like, no, like early life was actually evolving and adapting in really intense environments that had splashes and explosions and boiling water and toxic fumes and all the exciting stuff you'd see in Rotorua in New Zealand or places like that.

[00:30:26] So when I was trying to study this messy chemistry, I was really looking at modern day hot springs and spent a lot of time over in Rotorua and also up in the Himalayas in Ladakh.

[00:30:38] So this is like, you know, northern Himalayas studying these hot springs and the kinds of chemistry that they could boil up, all the rocks that I would dissolve on the ground and bring to the surface.

[00:30:49] And whether that has the diversity and the complexity needed for life to form.

[00:30:55] Yeah, I had a lot of time smelling like sulfur.

[00:30:58] And it's amazing.

[00:30:58] These environments are so reactive.

[00:31:00] There's so many reactive molecules bouncing around them.

[00:31:04] All your jewelry, like I've got like, yeah, like a nose ring and earrings and all that kind of stuff.

[00:31:09] And it turns black after a day of bouncing around these hot springs because the sulfur is so reactive.

[00:31:15] And there's this, everyone there, you see the real veteran hot spring researchers and they bring little kind of like plastic placemats to sit on on the ground.

[00:31:25] When they're like sitting cross-legged and doing their samples and that kind of stuff.

[00:31:28] I quickly realized there's this very embarrassing process called acid pants.

[00:31:34] And literally sitting on the ground, the ground is so acidic that it dissolves the stitching in your pants.

[00:31:41] And once every trip, there's definitely people who split their pants when they sit down.

[00:31:46] Because the acid literally in the ground dissolves your clothing.

[00:31:50] Like your boots are falling apart.

[00:31:52] Which makes it a very, you know, exciting place to work.

[00:31:55] But it's also that idea that that has the energy needed to create the drive of that life.

[00:32:02] You know, this wasn't just some backwater pool somewhere.

[00:32:04] There's so much stuff chemically going around.

[00:32:06] These places are so charged up with chemical potential energy that as soon as you have that little, you know, self-replicating bundle of chemicals, it can grab onto all these amazing chemical processes that are happening naturally.

[00:32:23] So wild.

[00:32:25] Yeah, you don't want to look green with holes in your pants on your trip.

[00:32:30] And to even think that these processes are still happening today, like the same, could it have happened more than once?

[00:32:39] Is it still happening today?

[00:32:42] Yeah, yeah, yeah.

[00:32:43] It's a really good question.

[00:32:44] I think when we talk about, you know, the origin of life and that whole kind of coming together of molecules, a lot of people say, hey, like, if that happened in just 300 million years, that 0.3 billion years at the beginning of the earth, why don't we sit at all the time?

[00:32:59] Why is that new life popping up everywhere?

[00:33:02] And there's a few questions.

[00:33:04] I think firstly, the earth was a lot more primed early on.

[00:33:08] You had, you know, a lot more asteroids in our solar system, which means more impacts, more delivery of organics, that kind of stuff.

[00:33:15] But the big thing is that life today is everywhere and it's hungry.

[00:33:20] As soon as you have some nice little bit of sugar or amino acid that's been delivered from space onto earth, very quickly, all the microbes are like, yes, here's a free source of chemical energy.

[00:33:33] And they're consuming anything.

[00:33:35] So I think that because life has evolved to be so competitive and just eat any free energy that's in its environment, you don't get the ability for having these nice potential primordial soups sitting around for a few hundred thousand years where they can start forming life.

[00:33:51] I think that any life on earth now just gets eaten up too quickly.

[00:33:57] And I guess, you know, like so many areas of science or biology, so many of these questions, even if we were to recreate it or observe it in nature or find evidence, like, would we know?

[00:34:12] Will we, can we know for sure what it looks like or what happened?

[00:34:17] Yeah, yeah.

[00:34:18] And I think that that's something that I really felt conceptionally towards the end of my PhD, you know, because you're looking as far back as we can go in time, you know, like literally the oldest rocks in the world.

[00:34:30] But even that was too late.

[00:34:32] Even the record started after all the exciting stuff that we're looking at happened.

[00:34:37] And there's this kind of philosophical concept of they call it like your grandfather's axe, where it's like, you know, your grandfather has an axe and your father inherits it and then they replace the handle of the axe.

[00:34:50] And then you take it and then the head of it's rusty, so you replace the head.

[00:34:54] Is that still your grandfather's axe?

[00:34:57] Because every component of that axe has been replaced.

[00:34:59] And we have that issue a lot in trying to figure out what life was like at the very beginning, because evolution has optimized and it's taken every single aspect of a cell and made it better.

[00:35:14] So the point that trying to look at a cell and say, what was the original cell?

[00:35:18] None of that architecture, none of the mechanics of that original cell possibly have survived the process of, you know, three billion years of evolution.

[00:35:27] And really like modern cells are that grandfather's axe, where every component has been replaced.

[00:35:33] And we really can't say for sure what it was like.

[00:35:36] So because of, yeah, the diminishing rock record that we can look back in time with and then how many updates life's had since then.

[00:35:44] We can make, you know, well-informed guesses.

[00:35:47] We can have a probability field and say there's a high probability that life was doing this as opposed to that.

[00:35:53] But in reality, we can't never know for certain.

[00:35:58] Yeah.

[00:35:58] Yeah.

[00:35:59] It doesn't exist in that status anymore.

[00:36:02] Yeah.

[00:36:02] And it would have, yeah, so many, so many iterations of those axes.

[00:36:07] Yeah, yeah.

[00:36:08] Honestly.

[00:36:08] Yeah, yeah.

[00:36:09] It was too good.

[00:36:11] It could have just slowed down a bit and let it.

[00:36:14] Yeah.

[00:36:14] Just fossilize for it.

[00:36:16] Yeah.

[00:36:16] And just going back out into space, do you think we're likely to find evidence on other planets?

[00:36:29] Yeah.

[00:36:29] I think that I've kind of got a twofold question there.

[00:36:33] I think that as we know, life started really early on on Earth.

[00:36:37] Like a couple hundred billion years is a blink of geological timeframes of the universe.

[00:36:43] It seemed to be as soon as the Earth had cooled down enough for life to form, life had formed.

[00:36:50] The thing that that process is remarkably complex and chemically amazing as that was, I'm sure that would have happened else.

[00:36:57] I'm sure there would have been little bubbles, you know, that were replicating and bouncing around on other planets.

[00:37:02] I think that's probability from a probability perspective has to have happened.

[00:37:08] What I find really interesting is the runaway evolutionary process that has led to complex life and led to all the stuff that we do now.

[00:37:18] Like you look at humans, like we make podcasts and we make jokes and we stress out of that love lives and we do complex maps.

[00:37:26] And like we've out evolved anything that we needed to just be a replicating primordial soup, you know?

[00:37:32] And even like you look at the mating habits of birds and you look at the complexity of ant colonies.

[00:37:38] I'm like life on Earth is just so diverse and so complex and so unnecessary.

[00:37:46] If your pure process is just replicating and carrying on your genetic material, we could have stayed a slimy map forever.

[00:37:54] We really couldn't, but we didn't.

[00:37:56] We exploded into the amazing stuff we see today.

[00:37:59] So, yeah, I think there's definitely slimy maps on other planets, but I don't know if any of them are making podcasts.

[00:38:05] I think that's where I was.

[00:38:08] Yeah.

[00:38:09] Yeah.

[00:38:09] Watching binary sunsets on some exoplanets.

[00:38:15] Yeah.

[00:38:16] Honestly, like we evolved to perceive beauty, you know?

[00:38:20] Like that is crazy.

[00:38:21] And I think that's why we're so unique and I think all life should be protected and valued because this could be the universe's only chance at perceiving the beauty of what it is.

[00:38:32] Agree.

[00:38:33] Agree.

[00:38:34] And just one last question for you.

[00:38:37] I'm not sure how you feel about this, but yeah, it's so interesting.

[00:38:42] The question of life in space transcends so many different areas, right?

[00:38:47] Like it's big in pop culture.

[00:38:48] It's big in art.

[00:38:50] It's big in, you know, scientists dedicate their careers looking for this.

[00:38:54] And we kind of hope that it is there, right?

[00:38:57] Like what do you think it is about this question that resonates so deeply with people?

[00:39:07] Yeah.

[00:39:08] It's a really, um, it's a really good question.

[00:39:10] And I'm still, I've definitely noticed it.

[00:39:13] And it's funny.

[00:39:14] I, um, I got into this field because anywhere you go, like someone's thought about aliens.

[00:39:21] You would be in the, I don't know, line for a port-a-loo at a music festival.

[00:39:25] Or you would be like chatting to friends you meet at a youth hostel in Argentina.

[00:39:30] And like someone's read a book, someone's seen something.

[00:39:32] Like it's kind of captivating at least an hour, you know, the last 150 years or whatever of

[00:39:38] human civilization.

[00:39:39] We've definitely, you know, been captained by this whole process, you know?

[00:39:42] And I think that being alone is scary.

[00:39:44] You know, I think we want to, for better or for worse, like we want to, there's a burden

[00:39:49] on being the only custodians of life in the universe.

[00:39:52] And I think we don't want to feel that burden and we don't want to feel that loneliness.

[00:39:56] And the idea that there's something out there that's greater than us, you know,

[00:40:00] this is kind of getting into a real theological aspect.

[00:40:03] But I think that for a lot of people, aliens and life on other planets fills that void of

[00:40:10] thinking about something bigger than them and something greater out there.

[00:40:14] And I think that that's a really innate human desire that, you know, permeates all aspects

[00:40:19] and cultures throughout time.

[00:40:21] And I think this is in our current society where space travel is so prevalent and we're

[00:40:26] seeing pictures from the Hubble telescope and people are sending Teslas into space.

[00:40:31] And it's at the forefront of our pop culture.

[00:40:34] I think that's taken over that niche of humans wanting to feel like there's something bigger.

[00:40:38] I think as humanity, like we're interested in this space.

[00:40:41] We want to know where we come from.

[00:40:43] We want to know, are we alone?

[00:40:46] Like these deep questions, you know, I love standing in that line for the port-a-loo and

[00:40:50] talking about it really unifies a lot of us in certain ways.

[00:40:53] So, no, I really love and appreciate this conversation.

[00:40:57] Thank you so much for taking the time.

[00:41:10] That was my conversation with Dr. Luke Stellar.

[00:41:15] Thank you for listening and thank you to Luke for sharing his work.

[00:41:19] Plant Kingdom is hosted and produced by me, Catherine Poults, and our music is by Carl Deiter.

[00:41:25] Listen to us wherever you get your podcasts and check out our website at plantkingdom.earth.