Gaia—A Holobiont-like System Emerging From Interaction

The Gaia hypothesis has been heavily discussed ever since its first formulation in the early 1970s. While parts of the hypothesis can be accepted right away, the optimizing view of Gaia as stabilizing conditions on Earth to support life on the planet has raised several doubts. In particular, the evolutionary aspect of conditions evolving in such an optimizing way is hardly in line with classical evolutionary theory. Considering Gaia as a holobiont-like system allows to clarify these issues. Accepting that every form of life interacts in manifold ways with its biotic and abiotic environments and that these interactions form a multilevel network from which higher-level properties can emerge, the self-stabilizing effect of the interactions of the biosphere with the geosphere and the atmosphere can be explained. With viewing evolution as adaptation of interaction and fitness as a shift in probability distribution of the observable, even the optimizing interpretation of Gaia does make sense and leads to valuable insight.