Abstract

Conrad Hal Waddington integrated genetics with embryology and evolution by formulating and providing experimental evidence for the mechanisms of canalization and genetic assimilation in the context of stabilizing selection, and by fostering an epigenetic rather than the prevailing gene-centered view of embryonic development and of evolutionary change in development and adult form. Waddington saw phenotypes as processes, not static structures and behaviors. Trained in geology at Cambridge, Waddington turned to experimental studies on the chemical nature of the primary organizer and developed the concepts of evocation and individuation as separable components of embryonic induction. A move after WW II to Edinburgh provided Waddington with his professional home for the rest of his career, during which he integrated genetics and development into an evolutionarily relevant discipline. Our conception of embryonic development as a highly integrated series of canalized pathways owes much to Waddington’s development of the concepts of canalization, chreods, epigenetics, and the epigenotype. The integrated, heritable, epigenetic organization of embryonic development is Waddington’s lasting legacy to development. He demonstrated organismal response to environmental change and hidden genetic variation, integrated environmental responsiveness into heritable change in response to selection, and coupled development, environment, and evolution