The organizer concept and modern embryology: Anglo-American perspectives

This paper analyses the origins of the Spemann-Mangold organizer concept of 1924 in relation to his earlier background and concepts. It traces the consequences and fate of the organizer, and related concepts (embryonic induction, gradients, fields) through subsequent phases in the evolution of developmental biology up to the present, primarily from a UK perspective, but also in the USA. The origins of Wolpert's concept of positional information of around 1970 are analysed; this markedly different model of embryogenesis effectively took the place of the organizer, following on from a generally assumed out-datedness of the corpus of Spemann's data and concepts. Explanations in terms of historical forces are suggested; events are seen as a historical causal chain. A crucial factor appears to have been the long-term neglect of morphogenetic cell movement as an integral component of an adequate induction-based model. The paper discusses the general inter-relation of history and science, and particularly the implications for current scientific practice, including the potential for conceptual distortions due to historical factors. It is argued that historical considerations need to be included as part of the use and critical assessment of basic concepts in science.