What is epigenetics : from Aristotle to Waddington ?

The first lecture reviewed the history of epigenetics - starting with the concept of epigenesis, the theory of development through the progressive elaboration of forms, first formulated by Aristotle four centuries BC. This theory was put forward in opposition to that of pre-formation, and was only validated experimentally many centuries later, in the 18th ^and19th centuries, thanks in particular to advances in microscopy that finally enabled us to observe the inside of the egg and the first cell divisions after fertilization. The ^twentieth century was marked by major revolutions in biology, both in experimental embryology and genetics. In 1942, Conrad (Hal) Waddington, a British scientist and philosopher, proposed merging the terms epigenesis and genetics to use the new nameepigenetics to designate the study of the mechanisms by which genes determine traits. Although our understanding of living organisms progressed spectacularly in the 1960s and 1970s thanks to molecular biology, the molecular links between genotype and phenotype only began to be truly elucidated several decades later, in the early 1980s.