Groundbreaking chemist defines all of life in 2 words | Lee Cronin

Sep 10, 2025

Lee Cronin, Regius Professor of Chemistry at the University of Glasgow, dives into the fascinating intersection of physics and biology. He discusses the concept of Assembly Theory, which explains how lifeless matter can become living systems. By using the Assembly Index, Cronin explores what molecular complexity can reveal about life, even beyond Earth. He provocatively argues that life can be defined by two fundamental ideas: existence and the ability to copy itself. Tune in to explore how these ideas connect rocks to dinosaurs — and us!

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INSIGHT

Physics vs Biology Gap

Physics describes a timeless, clockwork universe that can be run forward or backward.
That description fails to explain biology's novelty and open-ended evolution.

INSIGHT

Evolution Creates Continual Novelty

Evolution operates within the same physical universe but creates continual novelty like new species and technologies.
Bridging physics and biology requires a framework linking physical laws to evolutionary invention.

INSIGHT

Assembly Theory Bridges Rocks To Life

Assembly Theory explains how inert matter can become evolutionary through selection.
The theory provides a stepwise account of turning simple materials into complex, living systems.

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We don’t know what life is — even life on Earth. 🌍

Physics sees the universe as a timeless machine, unfolding like clockwork. But that doesn’t explain the creativity of biology — where new species, technologies, and cultures emerge all the time. 🧬✨

There’s a disconnect between the laws of physics and the wild, unpredictable evolution of life. Yet both exist in the same universe. Maybe it’s time we connect the dots.

Hi, I’m Lee Cronin, a chemist exploring how life began — from molecules to meaning.

Physics explains stars, gravity, and time. But it doesn’t predict biology. Darwin gave us evolution, but not how life *started*. That’s where **Assembly Theory** comes in — a new way to understand how lifeless matter becomes living systems.

Think of it like this: if you found a working iPhone on Mars, that’s weird. But 100 iPhones? That’s not random — it’s a sign of life. 📱🪐 Life is the ability to create complexity, at scale.

Assembly Theory breaks molecules down to atoms and asks: what’s the *minimum* information needed to build them back? That’s the **Assembly Index** — a universal signal of life.

NASA’s now testing this on meteorites to find signs of life beyond Earth. Because complexity, not Earth-like molecules, might be the true fingerprint of biology. 🔬🌌

Life is fragile chemistry that figured out how to **copy itself** — to keep existing.

In the end, life comes down to two things:

**existence and copying.** 🔁

That’s how we got from rocks to dinosaurs — and to us.

About Lee Cronin:

Leroy Cronin has one of the largest multidisciplinary, chemistry-based research teams in the world. He has given over 300 international talks and has authored over 350 peer-reviewed papers with recent work published in Nature, Science, and PNAS. He and his team are trying to make artificial life forms, find alien life, explore the digitization of chemistry, understand how information can be encoded into chemicals, and construct chemical computers.

He went to the University of York where he completed both a degree and PhD in chemistry and then went on to do postdocs in Edinburgh and Germany before becoming a lecturer at the Universities of Birmingham, and then Glasgow where he has been since 2002, working up the ranks to become the Regius Professor of Chemistry in 2013 at age 39.

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