Lascaux, which has been called "The Sistine Chapel of the Paleolithic", was discovered on September 12, 1940 by 18-year-old Marcel Ravidat when his dog, Robot, fell into a hole. Ravidar returned to the cave with three friends, Jacques Marsal, Georges Agnel, and Simon Coencas. The four re-entered the cave and discovered the splendid cave paintings on the walls of the cave. A few days later the boys told M. Laval, a retired schoolmaster, and Maurice Thaon, a young acquaintance of Abbé Henri Breuil, of their discovery. Thaon made a few preliminary sketches of the cave art and brought them to Breuil, the leading authority on paleolithic or cave art.On September 21, 1940 the four discoverers returned to the cave with Abbé Breuil. In his first exploration of the cave Breuil was acccompanied by prehistorians Denis Peyrony, Jean Bouyssonie and André Cheynier.

Breuil published the first preliminary scientific description of the cave and its paintings in Comptes rendus de l'Académie des Inscriptions & Belles-Lettres, September-October issue, 1940, as cited above. He also published a slightly more detailed account entitled, "Grotte de Lascaux. Rapport" in Bulletin de la Société historique et archéologique du Périgord (1940). Illustrations in that brief seven-page paper included reproductions of some of Thaon’s sketches.