# Selection Principles for Gaia

## TL;DR

This paper explores mechanisms behind Gaia hypothesis using a co-evolution model, proposing that Earth's increasing complexity and resilience result from entropic hierarchy and selection processes.

## Contribution

It introduces the concept of 'Entropic Gaia' by integrating selection mechanisms and diversity reservoirs within a co-evolution framework.

## Key findings

- Gaia may be driven by entropic hierarchy and selection processes.
- Increasing biomass and complexity are statistically likely features of co-evolving systems.
- The model suggests testable implications for Earth's history and astrobiology.

## Abstract

The Gaia hypothesis considers the life-environment coupled system as a single entity that acts to regulate and maintain habitable conditions on Earth. In this paper we discuss three mechanisms which could potentially lead to Gaia: Selection by Survival, Sequential Selection and Entropic Hierarchy. We use the Tangled Nature Model of co-evolution as a common framework for investigating all three, using an extended version of the standard model to elaborate on Gaia as an example of an entropic hierarchy. This idea, which combines sequential selection together with a reservoir of diversity that acts as a 'memory', implies a tendency towards growth and increasing resilience of the Gaian system over time. We then discuss how Gaian memory could be realised in practice via the microbial seed bank, climate refugia and lateral gene transfer and conclude by discussing testable implications of an entropic hierarchy for the study of Earth history and the search for life in the universe. This paper adds to the existing taxonomy of Gaia hypotheses to suggest an "Entropic Gaia" where we argue that increasing biomass, complexity and enhanced habitability over time is a statistically likely feature of a co-evolving system.