“Five years ago, Athol Fugard, the great chronicler of South Africa’s apartheid past and its post-apartheid present, heard a surprising tale. It was about a farm laborer named Nukain Mabuza, who had spent about 15 years, in the late 1960s and ’70s, painting vivid, highly patterned designs on the boulders and stones in arid terrain of the eastern province of Mpumalanga.”