Evolution and non-equilibrium physics. A study of the Tangled Nature Model

TL;DR

This paper uses computer simulations of the Tangled Nature Model to explore how non-equilibrium dynamics in biological evolution lead to increasing entropy, hierarchical organization, and stationary fluctuations, challenging traditional fitness concepts.

Contribution

It demonstrates that the Tangled Nature Model exhibits hierarchical punctuated equilibria with increasing entropy and introduces a coarse-grained description based on quake statistics.

Findings

Punctuated equilibria have increasing entropy and are separated by entropic barriers.

States are organized hierarchically, with stationary fluctuations when interaction ranges are limited.

Population growth is logarithmic, with decaying rates of change in macroscopic variables.

Abstract

We argue that the stochastic dynamics of interacting agents which replicate, mutate and die constitutes a non-equilibrium physical process akin to aging in complex materials. Specifically, our study uses extensive computer simulations of the Tangled Nature Model (TNM) of biological evolution to show that punctuated equilibria successively generated by the model's dynamics have increasing entropy and are separated by increasing entropic barriers. We further show that these states are organized in a hierarchy and that limiting the values of possible interactions to a finite interval leads to stationary fluctuations within a component of the latter. A coarse-grained description based on the temporal statistics of quakes, the events leading from one component of the hierarchy to the next, accounts for the logarithmic growth of the population and the decaying rate of change of macroscopic variables. Finally, we question the role of fitness in large scale evolution models and speculate on the possible evolutionary role of rejuvenation and memory effects.