[The cave at] Chauvet was a bombshell. . . . Its earliest paintings are at least thirty-two thousand years old, yet they are just as sophisticated as much later compositions. What emerged with that revelation was an image of Paleolithic artists transmitting their techniques from generation to generation for twenty-five millennia with almost no innovation or revolt. A profound conservatism in art, [author George] Curtis notes, is one of the hallmarks of a “classical civilization.” For the conventions of cave painting to have endured four times as long as recorded history, the culture it served, he concludes, must have been “deeply satisfying”—and stable to a degree it is hard for modern humans to imagine.