Waddington Conrad Hal

Conrad Hal Waddington (* 8. 11. 1905 † 26. 9. 1975) was a British developmental biologist, paleontologist, geneticist, embryologist and philosopher. He produced fundamental work on developmental biology and epigenetics. Waddington is considered an important forerunner of today's evolutionary developmental biology. The terms epigenetic landscape, canalization and genetic assimilation introduced by Waddington are common terms in genetics today.

Waddington was born to colonial British parents and spent the first three years of his childhood growing up with his parents on a tea plantation in India. At the age of three, he was sent back to England, where he grew up with relatives in Sedgeberrow, Worcestershire.

Waddington had a wide range of interests from a young age, including poetry. He cultivated close relationships with famous artists, including the British sculptor Henry Moore and the German Bauhaus founder Walter Gropius. In the course of his scientific career, he focused on developmental biology. In 1947 he was made a Fellow of the Royal Society and from 1947 was Professor and Head of the Institute of Animal Genetics at the University of Edinburgh. At this institute, Waddington worked consistently after the war on the concept of epigenetics, which he founded for the causal study of development. In 1958, he was appointed Commander of the British Empire (CBE). The American Academy of Arts and Sciences awarded him membership, as did the German Academy of Sciences Leopoldina. He was awarded honorary doctorates by the Universities of Montreal, Prague, Geneva, Cincinnati, Aberdeen and Trinity College Dublin. From 1970-71, Waddington worked at the State University of New York. He died of a heart condition two months before his seventieth birthday.

Waddington recognized that epigenetic mechanisms play an important role in heredity, development and evolution. He understood epigenetics as the sum of factors that act at the cellular, cell group or embryonic level to enable development, including genetic, internal and external environmental factors.

Waddington explained that genetic and epigenetic interaction is possible in such a way that an identical phenotype is formed or maintained despite mutations. This means that during development, several paths are usually created in order to produce a phenotype or a specific phenotypic characteristic. The large number of genetic alternatives is due to the fact that many genes are always involved in the development of a phenotypic trait in combination. Environmental stressors play an important role here, which can affect not only an individual animal, but the entire population.

Genetic assimilation: As a result, the stimulus may become unnecessary or only necessary to a lesser extent. The response of the entire system to the exogenous stimulus is such that it is relatively easily overwritten by already existing redundant, internal, genetic/epigenetic mechanisms and the system is thus genetically fixed, genetically assimilated (genetic assimilation). The external stimulus is no longer necessary to form the phenotype. Genetic assimilation has taken place.

In 1953, Waddington provided empirical evidence for his theses in the article "Genetic Assimilation of an Acquired Character", where he shows how the veins in fly wings disappear, triggered by repeated short heat shocks to the fly eggs over several generations, and how the veins eventually disappear in some animals even without the heat shocks. The change is assimilated in the development of the flies. The very short-term evolution of the beak shapes of Darwin's finches, as described by Peter and Rosemary Grant, is also associated with developmental changes, especially with changes in the Hsp90 protein.

The term epigenetics was first used by Waddington. Epigenetics, as he understood it, can be seen in today's terms as the transmission of certain traits to offspring that are not, or not exclusively, due to changes in gene regulation and expression during development.

1. Waddington Conrad Hal (1940) The genetic control of wing development in Drosophila. J. Genet. Vol. 39: pp. 75-139.
2. Waddington C H (1941) Evolution of developmental systems. Nature 147: 108-110.
3. Waddington C H (1942) Canalization of development and the inheritance of acquired characters. Nature 150: 563-564.
4. Waddington C H (1961) The human evolutionary system. In: Michael Banton (Ed.): Darwinism and the Study of Society. Tavistock, London
5. Lange A (2012): Darwin's legacy in transition - Waddington's epigenetics - A new view of development and evolution. Königshausen&Neumann Würzburg Ch.9:107-113.