Sarah Walker
speaker
510 appearances
1 recordings
1 series
first heard Jun 2024
last heard Jun 2024
Sarah Walker’s voice in public audio — every appearance, attributed to the second.
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I know. It's so hard. It's going from like a feeling to a visual to language is so stifling sometimes.
Yeah.
I hope so.
Yes. So self-reproduction has this property, right? Like if the system can make itself, then it can persist in time, right? Because all objects decay. They all have a finite lifetime. So if you're able to make a copy of yourself before you die, before the second law eats you or whatever people think happens, then that structure can persist in time.
Right. But things that can copy themselves are very rare.
And so what ends up happening is that you get structures that enable the existence of other things. And then somehow, only for some sets of objects, you get closed structures that are self-reinforcing and allow that entire structure to persist.
Right, so this is the classic idea.
And that's what we're trying to figure out is what are the causal constraints that close the loop. So there is this idea that's been in the literature for a really long time that was originally proposed by Stuart Kaufman as really critical to the origin life called autocatalytic set. So autocatalytic set is exactly this property. We have A makes B, B makes C, C makes A, and you get a closed system.
But the problem with the theory of autocatalytic sets is an incredibly... brittle as a theory and it requires a lot of ad hoc assumptions. Like you have to assume function. You have to say this thing makes B. It's not an emergent property, the association between A and B. And so the way I think about it is much more general. If you think about
um these histories that make objects it's kind of like the structure of the histories becomes um collapses in such a way that these things are all in the same sort of causal structure and that causal structure actually loops back on itself to be able to generate some of the things that make the higher level structures. Lee has a beautiful example of this actually in molybdenum.
It's like the first non-organic autocatalytic set. It's a self-reproducing molybdenum ring, but it's like molybdenum. And basically, if you look at the molybdenum, it makes a huge molybdenum ring. I don't remember exactly how big it is. It might be like 150 molybdenum atoms or something. But
But if you think about the configuration space of that object, you know, it's exponentially large, how many possible molecules. So, like, why does the entire system collapse on just making that one structure? If you start from, like, you know, molybdenum atoms that are maybe just, like, a couple of them stuck together. And so what they see in this system is there's a few intermediate stages.
So there's, like, some random events where the chemistry comes together and makes these structures large. And then once you get to this very large one, it becomes a template for the smaller ones, and then the whole system just reinforces its own production.
It's a... No, but I think it goes to the deepest roots of like when he started thinking about origins of life. So I like, I mean, I don't know all his history, but like what he's told me is he started out in crystallography. And, you know, there are some things that he would just, you know, like people would just take for granted about chemical structures that he was like deeply perplexed about.
Like, just like, why are these like really intricate structures
really complex structures forming so easily under these conditions and he was really interested in life um but he started in that field so he's just carried with him these sort of deep insights from these systems that seem like they're totally not alive and just like these metallic chemistries um into actually thinking about the deep principles of life so i think he already uh
And he already knew a lot about that chemistry. And he also, you know, assembly theory came from him thinking about how these systems work. So he had some intuition about what was going on with this molybdenum ring.
They knew about them for a long time, but they didn't know that the mechanism of why that particular structure form was autocatalytic feedback. And so that's what they figured out in this paper. And I actually think that paper is revealing some of the mechanism of the origin-life transition because really what you see –
Like the origin of life is basically like you should have a combinatorial explosion of the space of possible structures that are too large to exhaust. And yet you see it collapse on this, you know, really small space of possibilities that's mutually reinforcing itself to keep existing. That is the origin of life.
Yeah.
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