Every student of modern art knows how European and American avant-gardists of the early 20th century had their world rocked by Indigenous art—how they swooned over and strove to imitate the dynamic concision they saw in ethnographic exhibitions. How Picasso launched Cubism by sticking African masks on French prostitutes in Les Demoiselles d’Avignon . How Marsden Hartley paved his way to abstraction with tepees and Native American symbols. How Jackson Pollock started painting on the floor after