Thermodynamics of Darwinian selection in molecular replicators

TL;DR

This paper establishes fundamental thermodynamic bounds on the relationship between fitness, replication rate, and affinity in molecular replicators, with implications for early life evolution.

Contribution

It introduces a thermodynamic bound linking fitness, replication rate, and affinity applicable to various autocatalytic systems, advancing understanding of molecular evolution constraints.

Findings

Derived a thermodynamic bound relating fitness and affinity.

Bound the minimal fitness difference detectable by selection.

Applied the framework to classic replicator models.

Abstract

We consider the relationship between thermodynamics, fitness, and Darwinian selection in autocatalytic molecular replicators. We uncover a thermodynamic bound that relates fitness, replication rate, and thermodynamic affinity of replication. This bound applies to a broad range of systems, including elementary and non-elementary autocatalytic reactions, polymer-based replicators, and certain kinds of autocatalytic sets. In addition, we show that the critical selection coefficient (the minimal fitness difference visible to selection) is bounded by a simple function of the affinity. Our results imply fundamental thermodynamic bounds on selection strength in molecular evolution, complementary to other bounds that arise from finite population sizes and error thresholds. These bounds may be relevant for understanding thermodynamic constraints faced by early replicators at the origin of life. We illustrate our approach on several examples, including a classic model of replicators in a chemostat.