This lecture analyzes the emergence, in the mid-1980s, of a new discipline in biology that placed the evolution of animals in close relation to their embryonic development. Of course, this relationship existed long before that precise date, and many authors have been discussing this convergence since the 19th century, if not earlier. But this more recent period is characterized by the unexpected discovery of the genes controlling embryonic development and their extraordinary structural and functional conservation among animals as diverse as vertebrates and invertebrates. The notion of a general plan for the organization of the body from a genetic point of view emerged, providing evolutionary considerations with unhoped-for material, in particular for approaching questions linked to the mechanisms of variation, an area hitherto largely unexplored in evolutionary biology.
This lecture offers a brief retrospective of these experimental and theoretical developments, and an analysis of the main principles associated with this new discipline (but is it really a new discipline?). What have we learned as a result of these conceptual overhauls, and where is this evo-devo discipline heading? Will this fusion between two disciplines with such different fundamental rules stabilize and find a new equilibrium or, on the contrary, will today's extremely rapid technological developments of all kinds once again segment these two fields of investigation, as was the case at the dawn of the twentieth century with the emergence of causal embryology and, later, population genetics?