excavated from Tassili dates around 9,000 - 8,500 BP, while the Pastoral pottery is from 7,100 - 6000 BP. The rock art at Tassili is used in conjunction with other sites, including Dhar Tichitt in Mauritania, to study the development of animal husbandry and trans-Saharan travel in North Africa. Cattle were herded across vast areas as early as 3000 - 2000 BCE, reflecting the origins and spread of Pastoralism in the area. This was followed by horses (before 1000 BCE) and then the camel in the next millennium. The arrival of camels reflects the increased development of trans-Saharan trade, as camels were primarily used as transport in trade caravans. Prehistoric art The rock formation is an archaeological site, noted for its numerous prehistoric parietal works of rock art, first reported in 1910, that date to the early Neolithic era at the end of the last glacial period during which the Sahara was a habitable savanna rather than the current desert. Although sources vary considerably, the earliest pieces of art are presumed to be 12,000 years old. The vast majority date to the ninth and tenth millennia BP or younger, according to OSL dating of associated sediments. The art was dated by gathering small fragments of the painted panels that had dried out and flaked off before being buried. Among the 15,000 engravings so far identified, the subjects depicted are large wild animals including antelopes and crocodiles, cattle herds, and humans who engage in activities such as hunting and dancing. These paintings are some of the earliest by Central Saharan artists, and occur in the largest concentration at Tassili. Although Algeria is relatively close to the Iberian Peninsula, the rock art of Tassili n'Ajjer evolved separately from that of the European tradition. According to UNESCO, "The exceptional density of paintings and engravings...have made Tassili world famous." Similar to other Saharan sites with rock art, Tassili can be separated into five distinct traditions: Archaic (10,000 to 7,500 BCE), Round Head (7550 to 5050 BCE), Bovidian or Pastoral (4,500 to 4,000 BCE), Horse (from 2,000 BCE and 50 CE), and Camel (1000 BCE and onward). The Archaic period consists primarily of wild animals that lived in the Sahara during the Early Holocene. These works are attributed to hunter-gather peoples, consisting of only etchings. Images are primarily of larger animals, depicted in a naturalistic manner, with the occasional geometric pattern and the human figure.