Toy trains, loaded dice and the origin of life: dimerization on mineral surfaces under periodic drive with Gaussian inputs.

Rowena Ball,John Brindley

doi:10.1098/rsos.170141

Abstract

In a major extension of previous work, we model the putative hydrothermal rock pore setting for the origin of life on Earth as a series of coupled continuous flow units (the toy train). Perfusing through this train are reactants that set up thermochemical and pH oscillations, and an activated nucleotide that produces monomer and dimer monophosphates. The dynamical equations that model this system are thermally self-consistent. In an innovative step that breaks some new ground, we build stochasticity of the inputs into the model. The computational results infer various constraints and conditions on, and insights into, chemical evolution and the origin of life and its physical setting: long, interconnected porous structures with longitudinal non-uniformity would have been favourable, and the ubiquitous pH dependences of biology may have been established in the prebiotic era. We demonstrate the important role of Gaussian fluctuations of the inputs in driving polymerization, evolution and diversification. In particular, we find that the probability distribution of the resulting output fluctuations is left-skewed and right-weighted (the loaded dice), which could favour chemical evolution towards a living RNA world. We tentatively name this distribution ‘Goldilocks’. These results also vindicate the general approach of constructing and running a simple model to learn important new information about a complex system.

Highlights

Life on the present Earth is ubiquitous, except in the most extremely arduous physical conditions; the origin of this life, remains an unexplained phenomenon, though available evidence seems to support its occurrence in a relatively short window of time during the period between 4.2 and 3.8 billion years ago (4.2–3.8 Ga), and at a place and under physical and chemical conditions, all of which are uncertain and virtually impossible to verify from any currently observable evidence [1,2]
Despite the prodigious variety of living organisms, there is such similarity in their biochemistry and molecular biology to suggest the existence of a single last universal common ancestor (LUCA) [11,12]
There is currently a broad acceptance that, before the appearance of LUCA, prebiotic chemistry of polymerization reactions led through abiogenesis to an ‘RNA world’ from which DNA-based life evolved [13,14,15,16,17]

Summary

Introduction

Life on the present Earth is ubiquitous, except in the most extremely arduous physical conditions; the origin of this life, remains an unexplained phenomenon, though available evidence seems to support its occurrence in a relatively short window of time during the period between 4.2 and 3.8 billion years ago (4.2–3.8 Ga), and at a place and under physical and chemical conditions, all of which are uncertain and virtually impossible to verify from any currently observable evidence [1,2]. There is currently a broad (but by no means universal) acceptance that, before the appearance of LUCA, prebiotic chemistry of polymerization reactions led through abiogenesis to an ‘RNA world’ from which DNA-based life evolved [13,14,15,16,17]. Each stage of this complex evolution demands the availability of specific chemical constituents and the existence of particular environmental conditions.

The thiosulfate-hydrogen peroxide redox oscillator

Prebiotic reactions

Pore model

Results and discussions

Random is as random does

Conclusions