Lee Cronin on Assembly Theory: Quantifying Selection, Evolution, and the Emergence of Complexity Across the Universe

Lee Cronin introduces Assembly Theory, a framework designed to quantify the complexity of any object in the universe by determining the minimum number of steps required to construct it from elementary building blocks. A core tenet is that the "history is in the object," meaning its construction pathway is intrinsic to its nature. The theory posits that objects built through processes akin to evolution can be identified by their high assembly index and copy number, distinguishing them from randomly formed complex structures. This approach seeks to bridge the conceptual gap between fundamental physics and the emergence of biological complexity, suggesting that physics alone does not intuitively predict phenomena like life or human culture.

Cronin meticulously defines an "object" as finite, countable, decomposable, distinguishable, persistent, and breakable, with quantifiable construction constraints. He introduces the "assembly index" as the minimum number of steps on the shortest path to reproduce an object. A crucial distinction is made between four "universes": the Assembly Universe (anything goes), Assembly Possible (constrained by physical laws), Assembly Contingent (requiring work on a causal chain, no instantaneous access to future memories), and Assembly Observed (what we actually see). This highlights that true emergence requires a sequential, effortful process, not just theoretical possibility or instantaneous access to information, differentiating it from mere data compression.

The theory offers practical methods for measuring complexity, particularly for molecules, using techniques like mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance, which show correlations with the calculated assembly index. Cronin suggests that the "shortest path" in object construction is often favored by natural selection, as it represents the minimal information required for propagation and survival in dynamic environments. While the theory is still developing, especially for non-molecular objects like emojis or mathematical theorems, it provides a new lens for understanding how complex systems, from cells to cities, might optimize their construction pathways over time, even allowing for parallel processing and "assembly depth" to achieve overall efficiency.

Assembly Theory challenges traditional views by proposing a non-biological definition of "selection" and "evolution," arguing that these processes occur whenever an object persists in an environment while continually being destroyed and remade. This broader perspective has sparked controversy among evolutionary biologists and physicists, who often claim ownership over these concepts or dismiss the origin of life as self-evident. Cronin's work implies that the "factory" for selection emerges from the interplay between environment and objects, leading to increased robustness and the ability to propagate across diverse conditions, a hallmark of biological evolution. The theory opens avenues for understanding the emergence of alien life and intelligence, suggesting that while life may be ubiquitous, our "causal cones" might never overlap, leading to a profound sense of cosmic loneliness.

every star in the sky probably has planets Y and life is probably emerging on these planets but I think the commentarial space Associated to these planets is so different our causal cones are never going to overlap or not easily and this is a thing that makes me sad about alien life why why we have to create alien life in the lab as quickly as possible because I don't know if we are going to be able to be able to build um architectures that will intersect with alien intelligence architectures intersect you you know mean in time or space time and the ability to communicate the ability to communicate yeah my biggest fear in a way is that life is everywhere but we become infinitely more lonely because of our Scaffolding in that commentarial space

assembly Theory says that if we look at any object in the universe any object that we can quantify how complex it is by trying to find the number of steps it took to create it and also we can determine if it was built by a process akin to evolution by looking at how many copies of the object there are

the history is in the object

the assembly index if you to take the object apart and be super lazy about it or minimal say what it because you know it's like you've got a really short-term memory so what you do is you lay all the parts on the path and you find the minimum um number of steps you take on the path to add the parts together to to to reproduce the object and that minimum number is the assembly index

one big kind of um uh um kind of misunderstanding is assembly theory is telling you about how compressed the object is that's not right it's a how much information is required on a chain of events because the nice thing is if when you do compression in computer science we're wandering a bit here but it's kind of worth wandering I think in you you um assume you have instantaneous access to all the information in the memory yeah in assembly Theory you say no you don't get access to that memory until you've done the work and then you've done access to that memory you can have access but not to the next one

the assembly contingent says no you can't have access to the highly assembled object in the future until you've done the work in the past on the causal chain and that's really the really interesting shift where you go from assembly um possible to assembly contingent

I'm not saying there's some kind of woo woo memory in the universe you know morphic resonance or something I'm saying that there is an actual causal process that is being directed constrained in some way

the shortest path tells us something super interesting about the minimal amount of uh information required to propagate that Motif into time and space

scientists have grappled with reconciling biological evolution with the immutable laws of the universe defined by physics true right there's nothing wrong with that statement totally true yeah these laws underpin life's SW Evolution and the development of human culture and Technology yet they do not predict the emergence of these phenomena

I didn't think that biology evolutionary biology should be so bold to claim own ownership of selection and evolution and secondly a lot of evolutionary biologists seem to dismiss the origin of Life questions to say it's obvious and and that causes a real problem scientifically because when two different when the physicists are like we own the universe universe is good we explain all of it look at us and the biologist say we can explain biology and the poor chemistry in the in in the middle ground but hang on and this paper kind of says hey there is an interesting um disconnect between physics and biology and that's at the point which memories get made in chemistry through bonds and hey let's look at this close and see if we can quantify it

selection is the ability happens when an object survives in an environment for some time but and this is a thing that's super subtle the object has to be continually being destroyed and made by process

really the difference between inorganic abiotic selection and evolution and evolution and stuff in biology is robustness