Life sets off a cascade of machines

A fascinating PNAS article by Tiusty and Libchaber offers 'an oversimplified language of life.’ It is a long article, but I found it a very worthwhile read. (Motivated readers can obtain a PDF of the article from me.) Here I pass on the Significance and Abstract paragraphs, and the first figure. 

Significance

This paper follows an idea by Leibniz that life can be seen as an infinite cascade of machine-making machines, down to atomic machines. It proposes an oversimplified language of life, highlighting certain scaling aspects and the key step of self-reproduction, with a singular point at one micron and a thousand seconds.  (click on figure to enlarge)

 

Abstract

Life is invasive, occupying all physically accessible scales, stretching between almost nothing (protons, electrons, and photons) and almost everything (the whole biosphere). Motivated by seventeenth-century insights into this infinity, this paper proposes a language to discuss life as an infinite double cascade of machines making machines. Using this simplified language, we first discuss the micro-cascade proposed by Leibniz, which describes how the self-reproducing machine of the cell is built of smaller submachines down to the atomic scale. In the other direction, we propose that a macro-cascade builds from cells larger, organizational machines, up to the scale of the biosphere. The two cascades meet at the critical point of 10³ s in time and 1 micron in length, the scales of a microbial cell. We speculate on how this double cascade evolved once a self-replicating machine emerged in the salty water of prebiotic earth.