Monomer abundance distribution patterns as a universal biosignature: Examples from terrestrial and digital life

TL;DR

This paper proposes that the pattern of monomer abundances can serve as a universal biosignature, distinguishing life from abiotic processes by analyzing chemical concentration ratios in various environments, including terrestrial, extraterrestrial, and digital life systems.

Contribution

It introduces the concept of monomer abundance distribution patterns as a universal biosignature and demonstrates its applicability across biological, abiotic, and digital life forms.

Findings

Distinctive monomer patterns in biological samples

Abiotic samples show thermodynamic-dominated patterns

Digital life exhibits similar biosignature evolution

Abstract

Organisms leave a distinctive chemical signature in their environment because they synthesize those molecules that maximize their fitness. As a result, the relative concentrations of related chemical monomers in life-bearing environmental samples reflect, in part, those compounds' adaptive utility. In contrast, rates of molecular synthesis in a lifeless environment are dictated by reaction kinetics and thermodynamics, so concentrations of related monomers in abiotic samples tend to exhibit specific patterns dominated by small, easily formed, low-formation-energy molecules. We contend that this distinction can serve as a universal biosignature: the measurement of chemical concentration ratios that belie formation kinetics or equilibrium thermodynamics indicates the likely presence of life. We explore the features of this biosignature as observed in amino acids and carboxylic acids, using published data from numerous studies of terrestrial sediments, abiotic (spark, UV, and high-energy proton) synthesis experments, and meteorite bodies. We then compare these data to the results of experimental studies of an evolving digital life system. We observe the robust and repeatable evolution of an analogous biosignature in a digital lifeform, suggesting that evolutionary selection necessarily constrains organism composition and that the monomer abundance biosignature phenomenon is universal to evolved biosystems.