Sara Imari Walker
A lot of the books I have read in the recent past have to do with trying to get a working definition of life and/or consciousness. I picked up ‘Life as No One Knows It’ to get more perspectives in that direction, but it gave me something else by shifting the frame. At exactly halfway through the book, there is a line that goes “what will really be alien are examples of life (biological or technological) that have traversed a completely different evolutionary trajectory than we have.” And that’s important because if we keep looking for markers based on life on earth, we may not find it anywhere else in the universe. It’s thus important to find a framework that is agnostic of life as we know it, so that we have a measurable way of recognising and classifying signs of life/intelligence when we come across it.
Science has domains and subdomains and that has probably prevented it from looking at life in a more holistic way. Physicist and astrobiologist Sara Imari Walker is well placed to do that. Her approach to solving it is the Assembly Theory, a framework that tries to redefine our understanding of life through the complexity of objects and the informational processes that lead to their formation. The bias is thus more towards physics than biology, emphasising the former’s role in the emergence of complex structures. Life is information – from molecules to minerals to RNA to the artefacts we build. The theory, from what I understood, works around two concepts – assembly index, and copy number.
The assembly index is the minimum number of steps required to construct a specific object from basic building blocks, and copy number is the number of identical copies of that object exist within a system. The idea is that between these, we can determine the distinction between living and non-living entities. Objects with a high assembly index are associated with life since they are less likely to form spontaneously, and instead are more likely a result of information propagated across space and time, leading to the emergence of complex structures.
I preferred the first half of Life as No One Knows It (why and what) over the second part (how) because the latter got a bit too technical for me. The former had all of the stuff that interested me. For instance, entropy and the concept of negative entropy, free will and how we have it but not always, the ‘hard problems’ of consciousness (how and why physical processes in the brain give rise to subjective experience), matter (things can be observed only in terms of interactions) and life (that abstractions i.e. information matters in determining what can exist).
The origin of life is the unification point between biology and physics. It is where the universe described by the fixed laws of known physics – a universe without us – must yield to the seemingly endless forms of complexity generated in the evolution of our biosphere or any other. This unification must happen in what we call chemistry, because chemistry is the first thing the universe builds where not every object can exist. This leads to the possibility of an unfolding of different forms in different locations – what we might call different instances of “life”. Not all chemical possibilities can exist all at once; the ones that do exist must therefore be selected. This is why chemistry also happens to be where life can first emerge.
As our explorations in AI and space accelerate, a means to identifying and classifying life, both on our planet and elsewhere in the universe is important. ‘Life as No One Knows It’ provides a view of what is happening on that front. I felt that the first half was quite accessible, but the second half went into thesis mode.
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