Universal biology and the statistical mechanics of early life
Nigel Goldenfeld, Tommaso Biancalani, Farshid Jafarpour
Published 13 November 2017.DOI: 10.1098/rsta.2016.0341
All known life on the Earth exhibits at least two non-trivial common features: the canonical genetic code and biological homochirality, both of which emerged prior to the Last Universal Common Ancestor state. This article describes recent efforts to provide a narrative of this epoch using tools from statistical mechanics. During the emergence of self-replicating life far from equilibrium in a period of chemical evolution, minimal models of autocatalysis show that homochirality would have necessarily co-evolved along with the efficiency of early-life self-replicators. Dynamical system models of the evolution of the genetic code must explain its universality and its highly refined error-minimization properties. These have both been accounted for in a scenario where life arose from a collective, networked phase where there was no notion of species and perhaps even individuality itself. We show how this phase ultimately terminated during an event sometimes known as the Darwinian transition, leading to the present epoch of tree-like vertical descent of organismal lineages. These examples illustrate concrete examples of universal biology: the quest for a fundamental understanding of the basic properties of living systems, independent of precise instantiation in chemistry or other media. [To be published December 28, 2018, as part of the themed issue ‘Reconceptualizing the origins of life’.]
Rob Sheldon writes to say,
There’s a lot of circular reasoning in this abstract. We know that homochirality is needed to get alpha-helices and beta-sheets to form. These are the building blocks of enzymatic bonding sites. So if different chiralities were present, cells would have a terrible time making enzymes.
How to turn that design into a law?
“minimal models of autocatalysis show that homochirality would have necessarily co-evolved along with the efficiency of early-life self-replicator.”
Make it into a model. Voila! It had to be that way. No design needed. Models are the new statistics. Twain’s adage is now “lies, damn lies, and models”
Sheldon is riffing off “lies, damn lies, and statistics,” a phrase he attributes to Mark Twain but whose origin is — a quibble here — actually uncertain.
See also: What we know and don’t know about the origin of life