The essential aspect of life is adaptation to the job of self-replication through Darwinian selection. The entities performing this job are surprisingly complex non-equilibrium, self-organized systems. Nevertheless, complexity is not the goal. There is no inherent drive in evolution to increase individual complexity. Instead, individual complexity jumps up in rare evolutionary transitions. My own interest is the branching nature of evolution. Why ‘fittest wins’ leads to a “zoo” of different kinds of fittest? Certainly, this is not a gradient-dynamics. Our answer lies in the mathematical structure of self-regulating feedback loops of ecosystems. In a recent book we attempted to build the theory of ecology on this basis. The Holy Grail of ecological theory is understanding high-diversity ecosystems, like a rain-forest. My vote is the adaptationist one – not necessarily shared by everybody. Ultimately, biological diversity may, or may not, governed by some kind of self-organised criticality…