In 1973, Portuguese researcher Santos Junior gave the two largest sites their distinguishing names. Tchitundu-Hulu Mumule -- mumule meaning "man" -- is the larger, its engravings sprawling across the slopes of a 726-meter inselberg. At the summit, a rock shelter holds more than 180 paintings executed primarily in red and white pigments. Most of the art is geometric: concentric circles, parallel lines, abstract patterns carved into stone by perforation and abrasion. But among the geometry, Santos Junior identified four antelopes, two snakes, and a jackal during his visits in 1970 and 1972. Tchitundu-Hulu Mucai -- mucai meaning "woman" -- sits about a kilometer away. Its rock shelter, 6.7 meters high and 11.4 meters long with a depth of 11.3 meters, has been naturally oriented to shield its interior from wind and rain. The paintings here run to reds, blacks, and whites, with elongated forms that researchers describe as "sausage-like," alongside zoomorphs -- particularly felines -- that may depict hunting scenes.

Two smaller sites complete the complex. Pedra das Zebras -- Portuguese for "rock of the zebras" -- sits atop a low hill near Mumule and is the most modest of the four, consisting mainly of geometric circle designs. Pedra da Lagoa -- "rock of the pond" -- occupies a low hillside about a kilometer from Mumule and preserves two distinct groups of engravings, one significantly older than the other. The difference is visible in the depth and patina of the markings: older grooves are deeply weathered and darkened, while more recent work sits shallower in the stone. Together, the four sites represent a palimpsest of human activity in a landscape that is today sparsely populated and brutally arid. The engravings were made by perforating the rock surface or by abrasion, techniques common across southern African rock art traditions but applied here with a distinctive emphasis on geometric abstraction.

Dating the complex has proved stubbornly difficult. Radiocarbon analysis of excavated material at Mumule points to the first millennium BC, but pigment samples from the same site returned dates in the early centuries of the first millennium AD -- a span of a thousand years or more. Stone tools found at the site were attributed by archaeologists in the 1950s and 1960s to the Middle Stone Age and Late Stone Age, categories that cover an enormous temporal range. The authorship question is equally unresolved. Some scholars ascribe the complex to the Cuissi or Ova Kuvale, but neither group claims knowledge of who created the art. Other researchers suggest the sites were used by many different groups over long periods. Archaeologist Jose Camarate Franca first visited Mumule in 1952 and published his findings the following year. Henri Breuil studied the sites as part of the Archaeological Mission of Angola in the early 1960s, excavating Palaeolithic stone tools alongside the art.

Tchitundu-Hulu's remoteness has been both its protector and its threat. The rural isolation of Capolopopo has shielded the art from deliberate vandalism, but nature is less forgiving. The rock surfaces at Mumule are in an advanced state of decay, heavily eroded and prone to landslides that displace the engraved stone. Visitors walking over or near the engravings cause unintentional damage. Birds and insects colonize the rock shelters, and vegetation accumulates during the rainy season, accelerating deterioration. In March 2011, Angola's Ministry of Culture convened a workshop with international specialists to develop a preservation plan. On 9 May 2017, Tchitundu-Hulu was nominated for UNESCO World Heritage Site status -- recognition that these marks carved and painted on stone in a remote Angolan desert belong not just to an unknown people but to the world. Whether the art will survive long enough for that status to matter depends on preservation efforts that have barely begun.