Did painting originate from copying a shadow?

Roberto Casati and Patrick Cavanagh, "The Visual World of Shadows":

“…Shadows are a ubiquitous feature of our visual environment, in which so many objects block the light that is our principal source of information. Given their perturbation of light, and their high contrast, shadows are a massive problem for vision which must distinguish them from full-blown objects or material features of objects. Despite their nuisance, shadows are also an invaluable resource as their dance with light and their visibility can signal objects’ presence, location, shape, and size, among other properties. We know that much of the information from shadows is processed automatically and then may be accessed consciously, on demand, as it were. What is intriguing is that once used, shadows end up in the visual dustbin—they are hardly noticed or remembered—from where they can be retrieved only in certain special circumstances. Try to recall the shadows in the room you just left. Now go back there and look at all of them; you will see that most of them went unnoticed.

Because of the realism they offer and because of their visual and conceptual complexity, shadows have long fascinated visual artists: painters, graphic designers, movie makers…”

 

Gyges of Lydia inventing the art of drawing by tracing his shadow, 1573 as painted by Giorgio Vasari (1511–1574)

"...In Vasari’s The Origins of Painting, the light source is in a position such that it could not possibly cast the shadow of the painter’s profile on the wall. Actually, no light source is positioned anywhere in the scene that can possibly cast that very shadow, as the painter’s profile exactly matches the shadow’s outline. (Sure enough, the real shadow from that position would have been a poor portrait of the painter.) Observe that the painter’s face is in the shade, which means that his profile is definitely not casting his shadow as depicted. Nevertheless, the shadow seems appropriate at first glance..."