the University of Bordeaux and the University of the Witwatersrand together reported the discovery of the earliest known drawing by Homo sapiens at Blombos Cave, South Africa which is estimated to be 73,000 years old, much earlier than the 43,000 years old artifacts understood to be the earliest known modern human drawings found previously. There is a significant body of rock painting in the region around Matobo National Park of Zimbabwe dating from as early as 6000 BCE to 500 CE. Significant San rock paintings exist in the Waterberg area above the Palala River and around Drakensberg in South Africa, some of which are considered to derive from the period 8000 BCE. These images are very clear and depict a variety of human and wildlife motifs, especially antelope. There appears to be a fairly continuous history of rock painting in this area; some of the art clearly dates into the 19th century. They include depictions of horses with riders, which were not introduced to the area until the 1820s. Namibia, in addition to the Apollo 11 Cave complex, has a significant array of San rock art near Twyfelfontein. This work is several thousand years old, and appears to end with the arrival of pastoral tribes in the area. Horn of Africa Laas Geel is a complex of caves and rock shelters in northwestern Somalia. Famous for their rock art, the caves are located in a rural area on the outskirts of Hargeisa. They contain some of the earliest known cave paintings in the Horn of Africa, many of which depict pastoral scenes. Laas Geel's rock art is estimated to date back to somewhere between 9,000–8,000 and 3,000 BCE. In 2008, archaeologists also announced the discovery of cave paintings in Somalia's northern Dhambalin region, which the researchers suggest includes one of the earliest known depictions of a hunter on horseback. The rock art is in the Ethiopian-Arabian style, dated to 1000 to 3000 BCE. Other prehistoric art in the Horn region include stone megaliths and engravings, some of which are 3,500 years old. The town of Dillo in Ethiopia has a hilltop covered with stone stelae. It is one of several such sites in southern Ethiopia dating from historic period (10th–14th centuries). Saharan Africa The early art of this region has been divided into five periods: Bubalus Period, roughly 12-8 kya Round Head Period, roughly 10-8 kya Pastoral Period, roughly 7.5-4