C H Waddington, canalisation and genetic assimilation

Abstract

Conrad Hal Waddington was an English biologist who was among the earliest to emphasise that the proper understanding of multicellular development required an evolutionary approach. More than 50 years ago he carried out a series of experiments with intriguing implications for the evolution-development link. They appeared to demonstrate that it was possible for evolutionary change to take place and a qualitatively different developmental outcome to result without the action of selection on spontaneous mutations - that is, without the conventional neo-Darwinian route coming into play. The findings suggested that Lamarckian mechanisms might be at work, namely that acquired traits might be heritable. When Waddington is remembered today, it is for this set of experiments and for the explanation that he gave, which he named genetic assimilation. The explanation postulated that as a consequence of evolution, the course of normal development was canalised or buffered against perturbations. What follows is an informal and non-technical account of his work on genetic assimilation and his less successful effort to build a theoretical biology.