Big Ideas: The Origin of Life

Imagine for a moment that I hand you a book of molecules, essentially a soup of molecules. And imagine that this is very much dead. Now imagine I asked you to hang on to that book for a long time, because I'm going to tell you if you hang on to it long enough, life may emerge from it. Now what do we mean by that? How do you go from a disordered book of soup to an ordered book of life? And what do we even mean by life? Well, as you're here in this episode, there's lots of different definitions. But imagine for a moment it's something that can use information to respond to its environment. It's something that can make copies of itself. It's something that can evolve over many generations. The really interesting thing is how do you go from this book of disordered soup to something that's able to build order and complex structures? What is the mechanism by which that change happens? Well, on the show today, to talk about that is Sarah Walker, Deputy Director of the Beyond Center for Fundamental Concepts in Science, Associate Professor in Earth and Space Exploration and Complex Adaptive Systems at Arizona State University, and External Faculty at the Santa Fe Institute. Now Sarah's been on the show twice before. She's been on talking about information, and she's talked about time. And in reality, this episode, An Origin of Life, is the episode that brings those two concepts together. Because what you realize is that if you want to see how life has formed, you need information, and you need time. This is simplifying complexity. A podcast where we explore the underlying principles of complex systems, systems that seem to defy our rational view of the world, like economies, ecologies, or even you or me. I'm forensic engineer, Sean Brady, and I'll be your host. Sarah, welcome back on the show. Thanks so much for having me again. So you've been on before. You've talked about information. The last episode, when we talked about time, we talked about how really you're doing all this work to talk about the origin of life. So why don't we start there? What is the origin of life? And how did you get involved in this sort of research? I was an undergraduate in physics, and I really wanted to go to graduate school to be a theoretical physicist. And it was kind of a very nonlinear trajectory, because I don't have a history of scientists in my family. My dad's a hairdresser, and my mom was an antique dealer. So I went to community college. And it was just very funny, because I was like, I'll just take the size classes, and I took physics, and I just absolutely love the subject. I loved how we could build mathematical theories to predict future's a reality we never absurd, and then go out and look for them. And I just thought that was the coolest thing ever. So I was really hooked when I was 18 on this idea of becoming a theoretical physicist, because I just thought it was most elegant and beautiful way of working at reality. And I love what the human mind can do as far as comprehending things. So I went to undergrad, and then I went to grad school. And when I was in grad school, I was in a cosmology group in my PhD advisor. Really want to work on the original life. And I was like, what is that? I'm in a physics department, not a biology department, because I was very well trained as a physicist. And he nudged me to work on it. He's like, the conferences are in better places. And you might be able to get a better job. And I was like, I'll just work on this. So I can work with my PhD from Marcel Glazer. He's a great guy. And eventually, I'll be able to get back to cosmology once I proved that-- so I was trying to work on cosmology and origin life at the same time working with him when I started. But I think after a couple years, and really getting engrossed in the origin of life literature, I realized how hard a problem it was, and the fact that really no one had any conceptual footing to solve it. And if I thought about the real reasons I wanted to be a theoretical physicist, it was because I was so romanticized by these major transitions and are thinking about how reality works by this kind of introspection and these ideas that people had come up with over centuries and mathematically formalized and tested. And I wanted to be a part of that process. And I thought the origin of life was like the frontier for thinking about that. And so once I framed it in my mind that way, it was just so incredibly excited to work on the problem because it's so hard. And nobody really knows how to answer it. What is the problem, specifically, you're trying to solve? So you're talking about the origin of life. And what we know about life on this planet is it's all related evolutionarily. So we think all life on Earth is related by common ancestors. It's called the last universal common ancestor. Because it's the farthest back in time we can reconstruct a history of life on this planet where we find evidence that all life on Earth is related by this common ancestry. So it's sort of like the last horizon we can reconstruct genomically. We've done that? Yeah, we've done that genomically. Like we have some idea. I mean, this is actually a huge area of research is like what were the properties of the last universal common ancestor? We think it was cellular. We think it had DNA and translation machinery associated with the brightest zones and use proteins. So if you go far enough back in time, it gets really hard to understand what the properties of life are, but we have kind of a crude idea. And this crude idea is what we call the last universal common ancestor. And in fact, I tend to think about life more as this planetary scale process and not that the original life just happened in one isolated environment or one set of molecules. But it's actually the interaction of all sort of the processes that were happening at that timing chemistry across different scales from what might have been molecules that an individual say warm little ponds that Darwin described the original life environment being all the way up to planetary scale geochemical cycles. So most people in the origin of life have so far been doing what I described with the RNA world or metabolism first or these droplets is just trying to make the parts of life in the lab under so-called prebiotic conditions and I would put prebiotic in quotes. So that's sort of the standard approach in the field. And each one of those is kind of based on a sort of different definition for life. So genetics first type approaches RNA world are based on the idea that life is associated with our Indian evolution and sort of a popular definition people use is life is a self-sustaining chemical system capable of Darwinian evolution. So all these people have different definitions of life, but they always have the sort of same problems structurally as the definition I just gave based on Darwinian evolution. And what that boils down to is something that Carl Sagan actually pointed out in one of his essays about defining life is that anytime you try to make a definition of life, you always end up including cases you intended to exclude and excluding cases you intended to include. Take for example Darwinian evolution. Darwinian evolution seems encompassing of all life on Earth as we know it, but Darwinian evolution is something that only occurs at the level of populations. It doesn't happen in individuals unless you're counting like the evolution of microbes and might gut, but me as an individual certainly not evolving. And so if you assume Darwinian evolution is a key feature of life, no individual is life. Only populations are life. And then if you look at self-sustaining, self-sustaining is also interesting because you have to say, well, what does it mean to be self-sustaining and where do you draw the boundary? And so if you looked at say RNA in a test tube that can replicate and evolve, it's not self-sustaining because it might require a graduate student to pipette it into the next pipette. So it's got to rely on the graduate student as its environment to sustain itself. But even you and I can't self-sustain and total isolation recode dependent with an environment. And so that kind of excludes also again any individual thing from being life. So just to bring it back to this idea of life as a planetary phenomena, there's two issues of defining life. One is there's no hard boundary around the phenomena of life. So usually when we're approaching definitions of life, we want life to be a binary category. I know this thing's not life or this thing's life. And that's just not the way of thinking about it. Life is much more of a continuum. And when you get to the combinatorial space of chemistry, selection and information start to matter to explain why some things exist and not others because the space is so large, not everything can exist. Chemistry is the first place where this physics could become dominant. And that's what we call life. But that's not a-- it's life or not. It's just is this physics, the dominant physics or not. And then what are the kinds of structures you can build in this physics? So it's a very different framing of the problem. So I think the natural unit for thinking about life as far as life is information structuring matter across space and time or how life is how the universe builds complexity is a planet. A planet is a generator of life. And sometimes you get this open-ended cascade of complexity on a planet, sometimes you don't. And when you do, it's what we call life. And when you don't, it's a world that might have been alive. What makes a planet is it because you've got a closed system, but an energy source? Yeah, because everything on the planet has a cycling time scale for interaction. And I probably won't quote the right numbers. But I remember years ago reading a paper that was like about how long it takes for things to interact over what time scale is on the planet. So basically, depending on what time scale you care about, everything in the Earth is interacting with everything else. And you've got an energy source to drive that system. And if you think about life as this sort of deeper structure about how information is patterning the events that unfold, then the entire planet is a manifestation of that phenomena. And I think when you think about the original life, it might be the case that you actually Needles multiple timescale. and those multiple spatial environments over an Earth to generate a common autorial diversity of chemistry to actually mediate the original life transition. So the original life transition actually itself might be a transition in the geochemistry about planet. So let's talk about that because that is first thing. So it seems to me you're saying and tell me if you've got this totally wrong. Chemistry is the building blocks by which you achieve it, but the mechanism by which you achieve it if that's the right word is more of a physics mechanism that contains time and contains information and all of the things we've talked about before. And I you see in that the life we associate with us obviously and not here on Earth is chemistry based because chemistry just gave us a lovely diverse range of building blocks to be able to build life from. Yes, that's absolutely right and that's been saying but I would even take that concept one step further and say that we think the physical universe is large because we can look out and see you know 13.4 billion years or whatever away in our telescopes. It pales in size to the space of possibilities we can build on this planet just in chemistry. If we can convert sort of a physical dimension to a commonatorial space size. I mean that's kind of actually a hard mapping to make. But it's huge. It's just this unseen possibility space of what could be generated on a planet. And the origin of life transition is when complex objects start to be built in that space and complex objects are ones in assembly theory that we talked about are ones that require multiple steps for their synthesis and therefore they require some memory in the system in order to get to those objects. And so that already requires selection so that if you have a transition on a planet to selection selection can start building objects that require memory. And the building of those objects that require memory starts this cascade of now having more commonatorial parts that are already more assembled that build more structure and build more structure and build more structure. So there's this sort of transition that cascades to building more and more objects that have a larger depth and time or a larger size and time are more complex as a function of time. And that whole cascade is what life is but emerges from a planet and from the fact that the planet can't explore all possible chemistries and there's some transition where it starts to explore something slice of them and that structure actually starts exploring this entire commonatorial space of all these complex objects that you could never universe could never generate by exhaustive search. It has to do it by this depth first search of building on the complexity it's generated in the past which is what we call evolution because the space of possibilities is just too large. Yeah so you're saying like if you're putting molecules together randomly forever you don't get anywhere and you're saying that's when you move you're moving from that to selection. What do you mean by that? So I never liked the word selection originally I started adopting it because of to my colleagues a leachron and Michael Lockman really like using that word for like the mechanism of the original life and also obviously Darwin talked about selection so we know selection is an operative force in biology just to give a different framing of it I mean I'm happy with the word selection but the framing of it that I prefer is in some sense the physics of existence like why do some things exist and not others and the problem that you get in chemistry is not everything can exist so universe has to start making choices about what makes exist and it makes historically contingent choices because it can only build things based on structures that exist already so you can't just grab despite our imagination like we have this ability with our imagination to imagine this possibility space and just assume anything out of it can exist but there's certain things that we can't get to until we build the infrastructure to get there so for example humans were imagining rockets centuries before we built them because we had to actually invent engines and we had to invent lots of physics to or you know like Newtonian physics to actually allow us to understand how we could launch something with an engine into space right so there were a lot of contingent events that had to happen along the way before rockets became material objects they evolved over time based on past structures that were built and so this is a very general concept of evolution that evolution is the process that the universe uses memory of past objects to generate new objects I don't like states because that's a whole separate conversation so then for me the original life transition becomes one where if you think the universe is sort of trying to maximize the number of things that can exist it can do that by trying to do this exhaustive you know exploring all possibilities which is kind of what the second law of thermodynamics does or there's a transition that says well I can't exhaust everything I mean obviously anthropomorphizing my language here the universe doesn't have thoughts about this it's you know this happens right but like and I should be very clear on that because it's really hard not to anthropomorphize things about life we do it all the time we anthropomorphize everything but you could then think you're exploring now possible ways of building up objects and that you're selecting on the histories of those objects and so there's some transition in the physics where this becomes the dominant mode of what's happening and so if you think about selection as a force in nature like a gravitational force there's some critical density and chemistry of complexity that I think drives a transition where this force becomes the dominant force in physics and so that's a obviously really radical view but this is the way if you want to think about life at a deep level and you really want to solve the original life and you want to do it experimentally and be able to measure properties of this physics in the lab this is the sort of framing that you eventually end up that or one framing you end up that and obviously in the history of physics we've seen the case that we end up with these really deep abstractions that seem totally crazy but then we can go test them in the lab and they seem like they described the way reality really works so I think life is presenting that sort of scenario in this instance so you're fundamentally looking at at that port point we go from the randomness to the how is it the mechanism is that we're trying to get to how we go from starting to how use selection moving forward yeah so I think the mechanism is the universe wants to generate as many possible objects as it can so not everything can exist that's given so the universe has to select what exists and for simple objects it's easy to make all of them but for complex objects it's not easy to make all of them so then the universe has to in order to make more and more complex things and start exploring that possibility space you have to do it in a historically contingent way. Standard physics might say that a human brain could spontaneously fluctuate out of the quantum vacuum or a screwdriver could spontaneously fluctuate into existence on Mars and I don't think that's the case no one's ever observed that to happen it's an overstep of a generalization of current theories of physics I think the only kind of mechanism that can produce those kinds of complex objects is evolution and we never see those objects being formed in isolation they're always formed as part of this structure of many copies of that object being produced and it being produced part of this lineages or these evolutionary chains that are constructing more and more possibilities and so I would say that the physics of life is how the universe explores this huge vast common tutorial space of things that could exist where it can't make all of them and if it wants to make more and more complex ones and start to explore that broader space of more and more complex objects and it has to do so in a historically contingent way because if it doesn't build up the memory it can never get there and that's where the information in the time comes in and the critical features of understanding origin of life yes because the kind of things we are don't exist unless those are physical things in the theory so the kind of theory that will explain the existence of us has those as real fundamental properties because we're too rare in the space of possibilities if you actually went by standard physics you would try to do this breadth first search and all of us would just become trace very minute probabilities and some distribution overall possible objects which means our chances of existence are essentially mill because you know like if you think about all the ways of building you out of your atoms I mean you couldn't do that and God only knows how many universes right the probability of you just fluctuating into existence by just assembling them is just not possible and so then you want to say that there's many copies of you want to plan I mean I'm not identical to you but we're both humans and we're pretty similar physical structures so we're living on a planet where there's say you know like several billion humans you know what are the chances of getting several billion of us in the same very small volume of space if we're just a probability that's like this rare space and all possible things that people are you saying then that even though we've got a statistically you know a tiny chance of existing as a complete person our building blocks at the stage at which they got formed and the information they used to get formed over time that's where it starts to make sense there's statistically possible yes we became incredibly more likely to form one cells formed right because we're constructed out of cells so in the space of things that can make us there's a pathway that builds cells well there's lots of pathways of cells they're a physical feature of us it's not that I think that something like us is statistically improbable like that's what current physics tells us I think it's actually impossible outside of evolution I think the only mechanism the only physics that allows you to build things like us is evolution and it goes back to the time concept where we're talking about that if evolutionary objects have a size and time and there's a minimal time required for those objects to form but there's also the step to form those objects in a retention of the memory to form those objects that memory also gets used to make other objects in the space so it's easy to see with technology right so like transistors we're majoring innovation and technology. Now we use them in pretty much like all possible technologies. When something gets selected in the biosphere, it tends to get reused in different structures and actually affecting, constrain the future evolution of what emerges on the planet because it's easier to build things out of parts you already have than to invent things to not go. So there's obviously novelty, but most of the things are platformed on what's come before. So you think about this as a stack of objects, building objects using memories of the parts that are already known as how to build to build more complexity. It's a very historically contingent physics. - It's fascinating. It was we heard at Jeffrey West in the show, obviously talking about scaling and typically scaling in mammals and it was fascinating when you get to the rather obvious, but still I think surprising thing that, yeah, we're all build out of the same cells when it comes to mammals. And then that drives a whole pile of really interesting commonalities between us, even though we look totally different, they're an elephant in a way. - There's all kinds of things that are sort of common motifs that people apply in complex systems. And one of them is redundancy and another is modularity. So we use modules and we use them repeatedly. So a cell could be considered like a module part of something that gets repeatedly used in different contexts. But that's sort of a ubiquitous thing that we see in all kinds of complex systems. And I think when you're taking this sort of deeper perspective on the physics of life, it seems obvious that that should be a feature that we see ubiquitous in complex systems because the only way the universe can build those systems efficiently is if it's reusing parts it's made in the past. And if you think about the space of all possible objects that can exist and you think about all the ways of building those objects. So this is sort of a very assembly, theoretic concept, but I really like this idea. So I think it's worth talking about because I find it really exciting in a sort of beautiful way of thinking about the physics. But you imagine you have objects and you can build them up from elementary parts and that minimal depth is sort of where the first time you could possibly encounter that object. So it's like a minimal evolutionary threshold that the universe has to pass, a minimal memory before it can produce that object. Now most objects don't appear at their minimal, they're much longer trajectory to find them because assembly doesn't deal with the real history, just deals with the minimal history. So now you have a way though dealing with that minimal history of stacking all possible objects the universe could build by the minimal time it would take the universe to actually assemble that object. And so this is a way of now ordering all possible things by their evolutionary depth and time. And then we have this other feature that we think is important assembly theory which is the copy number, which is how many copies of that object do you find. So then you have these sort of two coordinates. If you think about the way we build physical theories, we need variables that we talk about. So we have a depth and time and then a number of the structures that have that depth and time. And this defines sort of the minimal amount of evolution to produce that particular set of structures. And the interesting thing is that in order to get to things that have a large depth and time and also large copy numbers, the only way to get there is actually to build using parts that you've built in the past. So you have to have selection to build structures like that. If you arrange the space of what's possible this way, and there's also a locality to it because it means that you and I are much more likely to coexist because we have a similar history than I would be with things I can't even imagine. You know, I'm not talking to an octopus right now because we're too different. But you can imagine some alien, like no evolutionary history in common, the chances of us spontaneously forming on a planet together are very low because we don't share common history. We don't share a common structure. Like we're not built in the same way. - Why is it relevant that there's seven or eight billion of us as opposed to 10 of us or one of us? - The hardest thing for the universe to do is to make one or two and then two to many. You know, like once you have many, you can just make many more. - So it's actually the zero to one and the one to two transitions that are most interesting. And actually, you're ready to pick up on this. This is actually the hardest thing for people to understand about what we're doing in assembly theory and why we focus so much on the copy number of objects. The fact that if you want to say an object is a product of evolution, like a molecule, it's not just that it's complex, it's that you see that as a repeated structure, that you see multiple copies of that molecule. The reason being that that excludes the possibility of random fluctuations. So like I was saying before, you know, standard physics would say there's a very low probability of anything happening. But if you want to say there's a low probability of screw drivers spontaneously forming on Mars, it's a very, very low probability, right? That the geochemistry of Mars is going to spontaneously assemble. What about if it made two screw drivers, right? That's an even lower probability. And if it made many screw drivers, so this gets at the issue of like, what is evidence of design? The reason that multiple copy numbers matter is that it suggests there's now a reliable mechanism for making that object, which suggests that the memory, the information necessary to constrain that entire possibility space of possible objects to that specific one, itself already exists as a physical object. So the copy number is direct evidence of this whole causal chain of things building up the memory to get to that specific object, because it means now there's a reliable mechanism in the universe for making that thing. Yeah, so it's a measure of the reliability of the mechanism. Which is evidence that the thing that built itself was selected, and then you get this whole chain of selected objects all the way down. And that goes all the way down to the universe selected elementary particles to exist. They already exist in multiple copies, but there are some objects like us that require much more time and much more memory to be acquired before we become reliable things for the universe to generate. Jump to the end. I've heard you talk about there's a lot to be, a lot to begin from talking about what the solution could look like. What does that mean? Yeah, so I'm really interested in solving the original life. And I guess going back to the beginning of this discussion, we're talking about these different original life theories. I think the problem I always had with them is they weren't solutions the origin of life. They were solutions to the problem of, how could this particular molecule that life uses possibly be generated in the absence of biology? But the problem with that approach is you're replacing biology now with technology. So instead of making the protein in a cell, you are, well, let's, we don't make proteins prebiotically, but like let's say you're making an amino acid. Instead of making a particular amino acid inside the cell, you're now making it inside a round bottom flask. And you're calling it prebiotic. And that's OK, as long as you're aware of the fact that the experiment itself is a product of evolution. And what I mean by that is if you, by this idea that life is about evolutionary lineages and objects building other objects, it's not just that my biological children are part of that lineage, but everything that I do is actually a product of this entire causal chain of things that have emanated since your original life on this planet. And we're all just kind of parts of these lineages. So the experimental boundary conditions would not exist in the absence of humans. And they certainly wouldn't exist in the absence of 3.8 billion years of evolution. So that's all fine. I think it's good as a proof of principle that this pH change can make this molecule, or UV light, might be important. It tells us some things about the features in the environment that can help make molecules. But it doesn't tell us about the original life process itself because we put too much life in the experiment. And then the question becomes, how do you build an experiment where you can control for how much information and time or life, whatever, praising you want to put, you put into the experiment. And this is a program that I'm working on with Lee Kronin, who is the original inventor of assembly theory. You can explore this vast chemical space that I've been describing. It's like, combinatorially huge, exponentially large, possible space in molecules. How would you know you actually created a set of molecules that are alive without a theory to guide you? And so assembly theory, really, the whole reason we've been developing it is to provide an agnostic tool to go in the lab and test whether the original life has happened in an experiment or not. And the kinds of experiments that need to probe that are actually to build essentially a chemical search engine. You want to try to explore as much chemistry as possible in as little time as possible to try to hit an alien original life event. And we don't know how rare life is in that space. So we might need to potentially do a lot of experiment. And we don't know what kind of chemistry we're going to have to explore. So part of this program is actually to build a digital platform for chemistry. And this is all stuff that Lee's done with a universal programming language for chemistry. So now you have a robot that can do any known chemical reaction in the literature and explore chemistry. And you have it in a universal language that allows you to describe the chemistry as an algorithmic process. And we have assembly theory that allows us to say, these molecules have no evolved complexity. And these molecules are evidence of evolution, because they're more complex. And so you take your molecules you put in the experiment, and you look at the unit operations you've done algorithmically by the actual chemical synthesis in the robot. And then you look at the complexity you get out. And you should be able to see how much information you put in as the boundary conditions of the experiment, because now you've encoded it in a sort of formal language. And you can actually see how much the chemistry generated in the complexity and the molecules. And what we want to be able to do is basically figure out how do we remove as much agency as possible? We've done as few experimental manipulations as possible control for many boundary conditions as possible to actually see how much the chemistry can generate on its own. And the whole experimental paradigm now is basically to ask if we could build a chemical experiment that studied. how information emerges, DiNabo, in chemistry, how would we actually bound that experiment and look for that? And so this is a way of actually approaching that problem. We're now, we've constructed it much more like a paradigm in experimental physics. We're looking for evidence of new physics. And we're trying to control the boundary conditions and not interfere with that physics as much as possible or at least quantify how much we've been affured with it. And is that they fundamentally trying to say I'm trying to create digital soup of molecules that will move into selection mode? It's not a digital soup. It has to be a physical experiment with real molecules. And there's two reasons for that. So people often ask me, could we simulate the original life in a computer? And I always say no. And the reason is because we don't know the physics. So what program would you put in to simulate it? If you don't know the physics, you can't actually build a model. And the other feature is that chemistry is so combinatorially large, it might be more efficient to actually run the experiment in the real universe and let the universe do the causal work and the computation to make new structures because chemistry is combinatorial and already built this way. Then it would be for us to program and run that on CPUs. We might not have enough computational power to actually explore the volume of possibility space that chemistry can just do. How far away are we from running this? Well, these running them in is lab right now. The question is we don't know how large a scale experiment we're going to need to do before we discover an original life event or how much stirring we have to do. So the whole paradigm is have artificial intelligence, algorithms, operating robots looking for evidence of high assembled molecules and changing conditions and selecting on basically increases in assembly and just changing the sort of mineral additions and TH change and trying to steer the chemistry that way. But also understanding how much are we actually doing as the selection autonomously from the outside. So if you can quantify how much selection you're doing and then you quantify how much the chemistry is generating, we're hoping that we'll actually be able to nail down the mechanism of the original life. And one way of talking about it sort of absence, like just maybe more in plain language is anything that rebuild is technically part of our biosphere and our evolutionary lineage. So the whole problem of the original life is to try to build an experiment that allows you to generate life as alien as possible from your lineage. When I was on like, "Sprieman, you did have this nice way of describing it as an information vacuum." Like you just want to not put that history into the experiment. You can't pinch it off entirely, but you want to pinch it off as much as possible from that history. So you say that weirdly when you make this experiment work, real success will be not only that you'll be able to get selection into it and it'll start to build complex things, but those complex things will be so fundamentally different to what we have, that that's proof the mechanism works. You're not trying to build the same in a way. You're just trying to build complexity. And that's one of the interesting questions. We're just trying to build the complexity. And it could be similar to Earth life as it naturally evolved on Earth billions of years ago, or it could be radically different. And we don't know because we don't know how convergent a process is on the solution we found on Earth. And this is also why I think this approach to origin life is much more interesting to me, because it's an experimental paradigm for testing that question. Right now in astrobiology, the only mechanism we have for looking for life elsewhere that most people use is to look for molecules life on Earth invented. And my thought is that most planets will uniquely evolve different biochemistry, because it's so geochemically contingent and there's so many variations early on in what molecules could kickstart that early selection process, that you could get radical divergences very early on. But now we have an experimental program that allows us to test that and test how much contingency there is. And let's say you produce new things that are different and have complex, yeah, that are alien complexity in them, is the idea that you then by studying the mechanism that produce that you see, and do we see evidence of a similar mechanism in the origin life here on Earth? Yeah, so we'll use it to inform understanding of the mechanism. But I think part of it is, you know, we have a theory that gives a measure. The theory already suggests some mechanism. So it just, it becomes a paradigm for testing the theory against experiment and iteratively looping between the two, because we want something that has to be measurable and have consequences that we can test in the lab. So we'll get results from the lab. We build them into the theory, the theory then produces new testable hypotheses, and we do that. We should ultimately come out with a theory that we can confirm in a meaningful way. And this is a really different paradigm for solving original life than what we've had traditionally, because we've been guided by definitions and just trying to like construct things based on definitions. And we haven't really shifted into this paradigm that's very standard in physics, where you have some deep theory and you build an experiment to test that theory. And so like, things like the Higgs boson, like, you know, some fundamental theory that predicts this should exist. We don't know. We build the large Hig-John collider, and we have to start ruling out different energy scales because we don't detect the Higgs there, but then finally, we isolate where the Higgs is. Gravitational waves, you know, we have a theory that predicts this should exist. We don't have the technology yet. So we have to start building into parameters over a period of 100 years to finally detect gravitational waves. And it's definitely the difference that a lot of the origin of life that's happening and it's traditionally happened in terms of research has been, I suppose, chemistry based and looking at chemistry and biology based, shall we say, looking at whether it's RNA or DNA or how molecules form. And what you're saying is, no, let's step outside that. Let's take a more physics approach to it. Let's find the mechanism that allows this to happen, because it's the mechanism that we're really chasing here. Yeah. And I should note, like, when you say it like that, it feels like disciplinary boundaries are real, right? But those are also human artifacts or some people that studied something we call biology, some chemistry and some physics. I mean, there's physics as a domain of study, which studies particles and the large scale structure, the universe and condensed matter systems and all these other things that physicists have traditionally studied. And then there's physics as a mode of thinking about the world, which builds abstractions that happen to be fundamental and quite deep and explanatory of a broad swath of phenomena. And that sort of method of doing science has traditionally been associated with physics, right? Because it's been most successful for those fairly simple systems and not the more complex chemistry and biology. But that method of doing science presumably should work in different domains that we apply it to. It's just the problems are harder when you get to the world of chemistry and biology. And it takes a lot more data, a lot more time to understand those patterns, which is probably why we haven't been able to build that abstraction yet, because abstractions themselves have a size and time and require a certain history to form just like life. Sarah Walker, thank you very much for being on the show. Thanks, it was fun. Thanks for listening to Simplifying Complexity. But we look at the key concepts of complexity science with expert minds from across the world. Concepts like emergence, self-organization, adaptation, networks, scaling, tipping points and much more. This podcast was produced by Brady Heywood and Weveland Creative. To make sure you don't miss an episode, be sure to subscribe to or follow the show in your podcast app. I'm Sean Brady and I'll see you in our next episode. 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