Sergio C Rubin, Michel Crucifix

Recent appraisals of the Gaia theory tend to focus on the claim that planetary life is a cybernetic regulator that would self-regulate Earth’s chemistry composition and climate dynamics, following either a weak (biotic and physical processes create feedback loops), or a strong (biological activity control and regulates the physical processes) interpretation of the Gaia hypothesis. Here, we contrast with the regulator interpretation and return to the initial motivation of the Gaia hypothesis: extending Schrödinger’s question about the nature of life at the planetary scale. To this end, we propose a relational and systemic biological approach using autopoiesis as the realization of the living and the (M,R)-system as the formal theory of biological systems. By applying a minimum of key categories to a set of interacting causal processes operating on a wide range of spatial time scales through the atmosphere, lithosphere, hydrosphere, and biosphere of the Earth system, we suggest a one-to-one realization map between the Gaia phenomenon and (M,R)-Autopoiesis. We show that metabolic molecular self-production by closure to efficient causation on a planetary scale is plausible. This suggests that the Gaia phenomenon may be the embodiment of Life itself in the planetary domain, a sui-generis biological unity and thus more fundamental than self-regulation by feedback mechanisms. Formulating the Gaia theory in biological terms provides a formal basis for the claim that planetary biology elsewhere in the universe must involve and have a formal equivalence to a self-referential physical process which cannot be implemented by a Turing machine and, therefore, has a non-computable character.