Abstract

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. 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...