The origins of modernist art are typically traced to Europe and a familiar roster of names, among them Manet, Cézanne, Matisse, Picasso. In the 20th century, however, things were brewing on other continents. In Brazil, starting in the 1910s, artists were creating a modernism shaped by the Afro-Brazilian experience. Now coming to London are 130 works by 10 South American pioneers. —Elena Clavarino