Commentary: The epigenotype—a dynamic network view of development

Abstract

During the late 1930s and the early 1940s, a particularly productive period in his scientific life, Conrad Hal Waddington (1905–75) started to construct a new synthesis between genetics, embryology and evolution. In the 4 years between 1939 and 1943, before he became involved in military activity during the Second World War, he published two substantial books and several seminal papers, all of which were explicitly geared towards constructing of an integrated view of biology. ‘The Epigenotype’, 1 published in 1942 in the semi-popular science journal Endeavour, is one of these papers. In it, Waddington presented and developed some of the ideas that he had already discussed in his books, and also defined, albeit informally, a new domain of research, epigenetics—the study of the causal mechanisms intervening between the genotype and the phenotype. Today, epigenetics is a very broad field of study, covering many aspects of biology, including morphogenesis, cell heredity, transgenerational epigenetic inheritance, and the evo-devo approach to evolution that Waddington investigated though his genetic assimilation experiments. In this commentary, we briefly discuss one particular aspect of Waddington’s epigenetic approach, the network-oriented view that he put forward in the 1942 Endeavour paper, 1 and the way in which this network view, Waddington’s epigenotype, is conceived today.