That is, can I paraphrase the sentence as 'Classical writers claimed that it was only after shadows had become an established, if controversial, part of representation that art itself had begun with the tracing of a human shadow.'? Or, does it just function as the main clause of that art itself had begun with the tracing of a human shadow.?
Shadows have been part of Western artistic practice since its origins. As far back as 32,000 years ago, prehistoric cave artists skillfully used modeling shadows to give their horses and bison volume. A few thousand years ago ancient Egyptian and then archaic Greek art presented human forms in shadow-style silhouette. But cast shadows do not appear in Western art until about 400 BCE in Athens. It was only after shadows had become an established, if controversial, part of representation that classical writers claimed that art itself had begun with the tracing of a human shadow. Greeks and Romans were the first to make the transition from modeling shadows to cast shadows, a practice that implied a consistent light source, a fixed point of view, and an understanding of geometric projection. In fact, what we might now call “shadow studies” ― the exploration of shadows in their various artistic manifestations ― has its roots in ancient Athens. Ever since, the practice of rendering shadows has evolved in tandem with critical analysis of them, as artists and theoreticians have engaged in an ongoing debate about the significance of shadow representation.
