Sara Imari Walker, Astrobiologist

Review: Life as No One Knows It: The Physics of Life's Emergence, a new book by Sara Imari Walker.

In 2021, the James Webb Space Telescope was launched amid great expectations and excitement about what we will learn as this telescope sees farther into the universe than ever possible before. Interest rose again about detecting life on other planets.

A new research team - astrobiologist and theoretical physicist Sara Walker and chemist Lee Cronin - became celebrities through their candid discussions of their science on the popular Lex Fridman podcast.

With their teams in Glasgow, Scotland, and Tempe, Arizona, respectively, this unique collaboration led to groundbreaking discoveries, not only for detecting alien forms of life, but also on the question of the origin of life on Earth.

Life as No One Knows It: The Physics of Life's Emergence, explores the history and accomplishes of science that led to the "assembly theory."

I’ve been poring over Sara’s book since it was released as audio and then bought a hard copy.

My primary interest is not in the popular pursuit of finding life on other planets, but in Sara's perspective about what we miss in studying life on this planet.

The most helpful thing to me about Sara’s book is her ability to describe the different fields of science and the limits of their guiding principles.

Sara suggests that new laws of physics is needed "...that include us as part of the system we are studying..."

As a theoretical physicist and astrobiologist, Sara has a qualified opinion about where science comes up short. It is in the preferred divisions between classifications of research. “Nature does not share these boundaries between disciplines.” (Walker, 30-31)

Biologists observe life; chemists say life is just chemistry; physicists focus on physical proofs; and computer scientists focus on copying life. Neuroscience is its own study of a physical system, not within the realm of physics. And what about genes?

For astrobiologists, there is a tendency to look for something that resembles what we know on Earth, meaning, forms that are familiar rather than alien. This is the critical failing of current physics, Sara writes.

Definitions held as core in each of the various scientific disciplines only confuses the search for the origin of life. Removing boundaries would allow us to detect life forms that bear no resemblance to what we know and therefore expect to find.

Sara says,

“…We cannot see ourselves clearly because we have not built a theory of physics that treats observers as inside the universe they are describing…explanatory power for how we think about and interact with the reality in which we live…

“…Life exists in biology and technology as far as we know, but we do not understand the transition or continuation of life from biology to technology, any more than we understand the continuation of life when chemistry transitions to biology… (Walker, 238-239)

This is why I love Sara’s perspective and her work. She takes on the truly hard problems that you and I can care about but is often not included from a scientist’s point of view.

What about us?

There’s a little humor in Sara’s good-natured criticism of her colleagues, those who say life is an illusion, or that life can be traced down to particles. Life is not a property of matter, modern science believes.

Yet you and I are pretty sure we are alive, so excuse us, science guys, “Being alive matters.”

Sara won’t let this difference go by the wayside. She aims to find out what makes matter alive. This is where she and Lee Cronin come together in assembly theory.

As a chemist, Lee Cronin starts with chemicals as the basic elements of all matter, living or nonliving. Can we reproduce in the lab the way molecules came together in the very first steps toward life?

Assembly theory finds that life is made by steps repeated, over and over, making and remaking objects - for generations. You and I are at least 3 billion years old, if you trace our lineage from the first evidence of life.

Sprinkled with analogies from Frankenstein to your coffee cup to LEGO blocks, Sara takes us into the histories that made science - and made us. Pushing out the boundaries of physics, she asks, why can’t information be a transformative element in human evolution?

As a feature of human evolution, information and knowledge and its historical lineage has also made a difference in the universe at large - footprints on the moon and satellites in orbit, as examples.

Assembly theory works backward from what we see in Nature, back to elemental building blocks that formed the initial bonds.

Living systems are recursive; they repeat the same steps over and over, and can be found in different places.

As the same steps (assembly index) are repeated, complex forms become more complex with slight variations as the elemental forms select properties that slightly increase the object's ability or improve its form.

Lineages are the histories from the elemental to the complex. Any complex object, then, is a product of its lineage.

An intriguing feature of assembly theory is how it proposes to qualify evolution further, looking for the shortest series of steps it takes to build “life.”

Assembly theory says that objects “are the things that you can build and break apart”; “current physics puts all causation at the microscale.” (Walker, 92)

By developing technologies, we can see, hear, and live beyond our physical limitations. This idea takes science much deeper into the nonphysical aspects of life, like information. There’s no such thing as a fluke of Nature in assembly theory. Everything has a lineage

Assembly theory allows for information as a critical feature in human evolution because it has consequences that can be observed.

Assembly Theory Basics

"... shifting focus from what life or consciousness is, to what these do, might open new ways to solve hard problems. The idea is pretty simple: Life is the only thing in the universe that are composed of many unique, recursively constructed parts."

These are the qualities of fundamental objects in assembly theory:

- Objects are finite and distinguishable.

- Objects are breakable.

- Objects exist more than once.

- Objects are lineages.

- Objects form via selection. (Walker, pp 88, 90-95)

The origin of life, says assembly theory, is in detecting the very first and simplest assembly process that forms an object. If a molecule has a sufficiently high number of bonds, and can also make many copies of itself, assembly theory says that the process may show how life took its first steps on Earth.

Sara's scientific pursuit of better knowledge about us humans as the highest form of life on Earth catches my attention...

However, Sara observes that humans have so little differentiation - we share 99.6 percent of our genome with any other person - that one person can only be considered a subset of humanity as a whole.

But what if physics were able to measure the 0.4% difference that appears in the "evolution" of one person, from their biology into their ideas and creations? If the phenomenon of the twelve phases does specify an observable transition - with an assembly index of 12 - via homeostasis and physiological responses? Would that ever catch the interest of science?

The lineage of personal advancement definitely exists in the physical. Only those boundaries around scientific disciplines - can I say "territories"? - limit our pursuit of understanding in that direction.

Lee Cronin's Lab

As a chemist, Lee Cronin’s research is always in the lab, and he requires absolute proof by lab testing. By this discipline, assembly theory has what other scientists need in order to verify the theory.

One piece of equipment Lee uses is a mass spectrometer ("mass spec"). (Walker, 121) It disassembles molecules into fragments and then breaks the fragments into parts again. (Wow, right?) Obviously, I can get lost here...

The point is, by breaking the molecule into fragments and looking at the number of unique parts, they could determine the minimal number of parts (assembly index) needed to build a molecule.

I followed Lee's fascinating Twitter (“X”) posts as he worked toward his remarkable “chemputer” to synthesize molecules. The chemputer randomly chooses molecules by an algorithm to see if they will create bonds. If some repeat the original sequence, a chain of life may begin. The key, of course, is for such bonds to repeat long enough to reproduce itself to begin building increasingly complex versions of itself. So far, they tend to die.

Sara considers the assembly index an intrinsic property of a molecule, essential to using the theory for solving the origin of life, as well as time being fundamental in making bonds in a series of steps, something like an algorithm.

(I say, yes. The twelve phases phenomenon that I have observed has the marks of a living system, including an algorithm, although we will be hard pressed to test it in a lab.)

The use of an algorithm brings a new dimension to the definition of matter. Sara explains that the computation is restricted to the rules of chemistry and steps that reflect "the minimal history of physically possible, recursive operations that must occur for an object to appear in the universe." (Walker, p. 132) In other words, a computation that can identify matter.

Through these and other ways of following their curiosity, Sara and Lee demonstrate the new physics Sara advocates. Throughout her book, Sara brings many enlightening facts forward from the history of scientific breakthroughs and lives of original thinkers.

I highly recommend Life as No One Knows It: The Physics of Life's Emergence to anyone who wants to stay in tune with the latest in free thinking and pure science.

For those interested in the search for alien intelligence, Sara covers the subject in a straightforward and science-based manner, touching on some fascinating little-known background and relevant news coverage.

Because of Sara Walker’s expansive coverage of many aspects of science, I’ll be digging into her book again and again to check my bias.

Stay tuned to see where assembly theory pops up in the 12Phases blog.

Cheers!

Elizabeth Diane

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Referenced in this blog:

Life as No One Knows It: The Physics of Life's Emergence by Sara Imari Walker. Available as an audiobook read by the author.

Nasa’s James Webb Space Telescope

The Lex Fridman podcast episode #279 with Sara Walker and Lee Cronin.

Lee Cronin on Twitter (“X”) @Leecronin