Here is an idea that might just explain the process used by prehistoric man to paint the walls of caves; a simple idea born from the observation of a shadow projected on the wall of a child's room. And it is a discovery that comes ridicule the most outlandish theories "specialists" who imagined, among other theories, these prehistoric art schools and artists traveling through the countryside as did the itinerant painters to 17th / 18é centuries in our campaigns to decorate churches. Prudent and humble, the author, a passionate graphic designer but not pre-historian, experimented on the wall of his basement and in the dark, its projection method with an oil lamp to draw relate to rapid and completed its verification by drawing d other people with the same surprising results. I will not dwell on the very negative or absent reaction, "experts" when he proposed to them, without arrogance, his idea. A great adventure of intelligence and common sense and that made me think the myth of Plato's cave: it is difficult to escape the "experts" to light, these Diafoirus frozen in their academic certainties and "learned "publications. Read to view cave paintings with an intelligent eye of true amateur.