How do fitness and natural selection relate to other evolutionary factors like architectural constraint, mode of reproduction, and drift? In one way of thinking, drawn from Newtonian dynamics, fitness is one force driving evolutionary change and added to other factors. In another, drawn from statistical thermodynamics, it is a statistical trend that manifests itself in natural selection histories. It is argued that the first model is incoherent, the second appropriate; a hierarchical realization model is proposed as a basis for a (...) statistical treatment. It emerges that natural selection does not cause evolution; it just is evolution. The theory incorporates relations of statistical correlation, but not the kind of causation found in fundamental physical processes. (shrink)

This paper contemplates Organicism and its relation with molecular and evolutionary biology. We explore whether twentieth-first century biology is returning to positions held at the beginning of the twentieth century and then abandoned. The guiding line is a history of theoretical biology in which we distinguish three periods: 1. The 20s-30s, and the Theoretical Biology Club (Needham, Woodger, and Waddington, among others); 2. An intermediate period in the 60s-70s, in which, in spite of the eclosion of the molecular and evolutionary (...) biologies, there is some recovery of organicist positions, and 3. The present post-genomic situation, which is demanding a systemic approach. (shrink)