Robustness from top to bottom

Robustness is one of the fundamental properties of living systems that is observed ubiquitously among different species and at different levels. In Robustness and Evolvability in Living Systems, Andreas Wagner attempts to provide a conceptual framework for understanding robustness in biological systems. The main thrust of his argument is that robustness against mutation can be explained by the existence of multiple solutions to a particular biological problem. Mutations can thus be selectively neutral. Wagner argues that “a neutral space is a collection of equivalent solutions to the same biological problems. It can also be thought of as a set of alternative configurations of a biological system, configurations that solve the same problem.” This idea is developed to explain the robustness of living organisms at different levels. Chapter 1 discusses “robustness below the gene level” and describes how the neutral space concept can be applied to explain robustness against changes in DNA, RNA and amino acid sequences. Chapter 2 discusses “robustness above the gene level,” providing examples from fly, sea urchin and worm developmental and metabolic networks. Chapter 3 reconciles examples in Chapters 1 and 2 into a unifying perspective of neutral space, as well as developing arguments on evolvability and robustness. Chapter 4 is about “robustness beyond organisms,” extending the arguments to ecology and self-organization.