What if there was more to it than luck? What if the Earth system possessed self-stabilising or homeostatic processes that reduce the magnitude of impacts on life? This is a form of the original Gaia Hypothesis first proposed by James Lovelock nearly half a century ago. Since then many articles, books and popular press reports have been published. Initially written off as 'not even wrong', the hypothesis has persisted in one form or another. What has remained is what appears to be a lack of any mechanism by which planetary-scale homeostasis could operate.

In this talk, I will give an overview of a mechanism for Gaian homeostasis. The mechanism operates if a few simple assumptions are satisfied. In outlining this mechanism, I will give an overview of the Gaian debate, how it relates to evolutionary biology, Earth system science, and where luck and anthropic principles play a role in our attempts to understand the evolution of the Earth, and other planets with biospheres.