The unsolved problem — the origin of morphological novelty

Abstract

The neo-Darwinian approach to the analysis of evolution is based on a mathematics which reduces the entire process to the study of changes in gene frequencies within populations, assuming that such changes can, by extrapolation, eventually explain all evolution. Here, the organism has, in effect, been discarded and only lip service is paid to the developmental interactions necessary for producing the required changes in phenotype. In the case of microevolutionary changes, involving essentially quantitative alterations within populations through time, this is of little serious consequence. But in respect of macroevolutionary change, involving complex shifts in phenotype of the kind required for the formation of the major eukaryotic taxa, it fails to address the real issue. Since all biological structure is the result of developmental processes, it follows that all phenotypic structural change must originate through changes in development. This, in turn, implies that the only sensible speculations about the origin of the various eukaryotic phyla, classes and orders must be based on developmental considerations. Thus, phylogeny unfolds historically as a sequence of modified ontogenies involving descent with modification.

‘What men want is not knowledge but certainty.’Bertrand Russell