Chris Kempes: commitment

Transcript context

…Can we talk about assembly theory? So you've got a paper out about this, and it's a way of kind of quantifying complexity, I suppose, by looking at how something can be built step by step. Can you explain what that is? Yeah. So this is a theory initially aimed at trying to search for life in the universe. So chemist Lee Cronin and a theoretical physicist, Sarah Walker, and then a bunch of other of us who've gotten involved, were have been interested in this idea of how do you fairly and without being committed to this past knowledge I was talking about before, the biochemistry we have, how do you fairly look for life in the universe? And so assembly theory simply says 1 way to do that is to look at the recursive use of parts and what the shortest path to build an object is, right? And so here's the thing you're trying to get away from. I hand you a molecule, and I say is this molecule complex? And I don't, I'm not allowed to tell you anything about the synthesis that we use to make it. I'm not allowed to tell you if a living system made it, I'm not allowed to tell you if that living system shares our biochemistry, has different biochemistry. How do you decide if that molecule is complex or not? And what we want is something that bounds that complexity, right, we want sort of an ultimate bound in that complexity. And 1 way to do that is just to say, when you have a synthesis pathway, so you have an evolving set of objects that are following some evolutionary lineage, you invent a set of parts, and then the easiest thing to do is take those parts and reuse them in some way, right? And then if you invent a new part, that's sort of a more complicated thing to do. With that sort of notion in mind, you could say I give you an object and you're just trying to find the shortest path to build it where you build up a set of parts and then can recursively use those to make a next set of parts, and you ask how often you have to build a new part or use an old part, each of those counts as a step and you're just trying to find this shortest path to get something. And that's definitely a bound, Certain processes could take, could be much more complicated in building that up, but it sort of lower bounds the complexity, and then by comparing all these lower bounds of complexity, you can sort of fairly compare how complex an object is in the best case sort of shortest path process. And so this gets away from things like if I hand you carbon 60, which has a large molecular weight, you could say, well, that's a very big object, but it's actually not so complex in those terms, right, in this assembly theoretic perspective. And so experimentally, it looks like there's, and this is work that Lee's done in his lab, it looks like there's a threshold where you can go from abiotic to the biotic. Each step in the STEMLI space is in a very rapidly growing space of combinatorial possibilities, so each step is a really big step. And so to have, you expect sort of a sharp cut off there somewhere, and it looks like that happens in the experimental data, which is exciting. Chris, this has been absolutely amazing. Thank you so much for joining us.…

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