A Commentary on Blute’s ‘Updated Definition’

Denis Walsh* Barely a decade after the discovery of the chromosomal basis of inheritance, and the articulation of the genetical theory of population change, the gene came to be widely regarded as the fundamental unit of biological organization. This is hardly surprising. The gene concept is a powerful one; it plays a unifying role in our understanding of evolution. Darwin told us that evolution by natural selection occurs in a population when organisms survive, die and reproduce differentially on account of their heritable form (what we now call ‘phenotype’). This is a very schematic theory. It requires an account of the process of inheritance and also an account of the generation of phenotype. The gene concept plays a prominent role in explaining, and uniting, these phenomena. Genes are the units of inheritance; they are passed from parents to offspring in reproduction. Moreover, they are seen as units of phenotypic control. Evolutionary biologists often speak of the genome as a program for the production of an organism. Genes also became the elements of which populations are composed. Our best theory of population dynamics—inherited from Fisher, Haldane, and Wright—is a theory of changes in the relative frequencies of gene types. Genes are not just the principal causes of evolutionary change, they are also the units over which evolutionary change is defined and measured. So, at least, the orthodox reading of the Modern Synthesis theory of evolution would have us believe. The successes of this gene‐centred evolutionary biology hardly need recounting. But one may celebrate its successes without succumbing to its excesses. Since the 1980s an alternative movement in evolutionary biology— evolutionary developmental biology (‘evo‐devo’) and ecological‐evolutionary‐ developmental biology (‘eco‐evo‐devo’)1—has been gaining prominence. Evo‐ devo seeks to rein in the rhetoric of gene‐centred biology, and to offer a more realistically organism‐centred perspective on the process of evolution (Callebaut, Muller and Newman 2007). Marion Blute’s revised definition of evolution by natural selection is a contribution to this conceptual reconfiguration of evolutionary biology, and a welcome one. Professor Blute proposes that we think of evolution by natural selection in the following way: