Dec 9, 2023, 4:14 PM ETInterview, Podcast

Lee Cronin: Controversial Nature Paper on Evolution of Life and Universe | Lex Fridman Podcast #404

Definition of an Object: An object is defined as finite, decomposable into subunits, distinguishable, persistent over time, and breakable such that its construction constraints are quantifiable.
Assembly Index: The minimum number of steps required to build an object from elementary building blocks, representing the shortest causal path to create it.
Copy Number: The quantity of identical copies of an object; high copy numbers for high assembly index objects indicate non-random selection and the presence of a "factory" or production mechanism.
The Assembly Equation: Quantifies selection and evolution by combining the assembly index and copy number of an ensemble of objects to measure the total selection required to produce them.
Four Universes of Assembly:
- Assembly Universe: A combinatorial space where anything goes without physical constraints.
- Assembly Possible: Constraints of physics (e.g., bonds) exist, but motifs are accessible instantaneously without causal history.
- Assembly Contingent: Causal chains are required; access to future motifs is impossible until past work is performed (the realm of physical reality).
- Assembly Observed: The subset of contingent objects that actually exist, allowing us to work backward to infer their history.

Measurement via Spectroscopy: The assembly index of molecules can be measured experimentally using mass spectrometry, infrared spectroscopy (fingerprint region), and nuclear magnetic resonance (NMR), which correlate with calculated assembly indices.
Life Meter Concept: A device combining mass spectrometry and infrared spectroscopy to detect complex molecules with high copy numbers, serving as a universal detector for life without Earth-biased biomarkers.
Thresholds for Life Detection: Molecules with an assembly index greater than 15 (or mass >350 Da) with high copy numbers (e.g., >10,000 identical copies) act as evidence of selection, distinguishing biological artifacts from random abiotic chemistry.
Tree of Life Reconstruction: Assembly theory has successfully recapitulated the evolutionary tree of life using mass spectrometry data without DNA sequencing, by analyzing the "joint assembly space" of co-existing molecules.
Dating and Decomposition: The theory suggests the potential to date biological samples by analyzing molecular decomposition rates, chirality changes (racemization), and isotope enrichment (e.g., Carbon-13 kinetics) over time.
Application to Non-Chemical Systems: The framework is being extended to emojis, images (pixel arrays), language, mathematical theorems, and cellular automata to measure complexity across different scales.

Criticism from Evolutionary Biologists: Critics argue that the origin of life is a solved problem and that the theory redundantly redefines selection without adding predictive power; the author argues the origin of life remains unexplained by current biological frameworks.
Criticism from Physicists: Physicists challenge the notion that initial conditions cannot predict the future, arguing that physics should explain all emergence; the author counters that the universe is too large to contain the future, necessitating time as a fundamental resource.
Distinction from Kolmogorov Complexity: Unlike algorithmic information theory, which measures the shortest program to generate data, assembly theory measures the causal history and physical steps required, emphasizing construction over compression.
Rejection by Journal Reviewers: The paper initially faced rejection and accusations of fraud from chemists who believed complex molecules could form randomly; it required years of revision and persistence before publication in Nature.
Response to "Obviousness": The author contends that while the concept of selection is intuitive, no prior quantitative mechanism existed to measure it via assembly and copy number in a universal, testable way.

Fundamental Time: Time is proposed as a fundamental resource because the universe is "too big to contain itself," meaning the future cannot be fully specified by initial conditions due to finite precision limits in physical objects.
Non-Determinism: The universe is deterministic looking backward but non-deterministic looking forward; the gap between past constraints and future possibilities creates space for novelty and creativity.
Life as Novelty Mining: Life is defined as a mechanism that mines novelty from the future, actualizing unpredictable configurations that were not encoded in the past.
Alien Loneliness: Due to vast "commentarial space" and distinct causal cones, alien civilizations with different evolutionary scaffolds may be infinitely lonely and unable to communicate or intersect intelligently, even if life is common.
Prediction of Causal Overlap: While current causal cones of alien life may not overlap, the author hypothesizes that as intelligence and abstraction grow, these cones may eventually expand enough to allow intersection.

Rejection of AI Doomerism: The author dismisses the "AI extinction" scenario (e.g., paperclip maximizer) as a category error, arguing that current AI lacks genuine intention, agency, and the ability to generate novelty from the future.
AI as Interpolation vs. Innovation: Current Large Language Models (LLMs) mine the past (interpolation) and cannot generate truly novel knowledge without external human intent or training data.
Chemical Brains: The author proposes "Chem Machina" as a project to build intelligent systems using wet chemical hardware to achieve domain flexibility and true reasoning, mimicking the evolution of biological intelligence.
Drug Discovery Application: Assembly theory can constrain drug discovery by focusing on molecules that evolve over time, shifting focus from static protein binding to dynamic molecular networks.
Electron Density Modeling: The author's team developed a GPT-like system that generates electron densities for novel molecules, effectively using "hallucinations" (extrapolation) to design new drugs that bind to specific protein sites.

Learning Difficulties: Lee Cronin overcame significant academic struggles, including being labeled as having learning difficulties and being barred from advanced math exams, by persisting in first-principle thinking and experimentation.
The Creative Force: Cronin identifies "selection" as the fundamental creative force in the universe, driving the persistence of objects and the generation of novelty against the tendency toward entropy.
God and Belief: While an atheist, Cronin believes in a "creative force" within the universe; he views the concept of God as a human-created abstraction resulting from selection, similar to how humans create the concept of superintelligence.
Free Will: Free will is situated at the boundary of the present and future, allowing agents to explore narrow trajectories and build novel architectures rather than following a predetermined script.