Tassili-n-Ajjer in Algeria is one of the most famous North African sites of rock painting. Its imagery documents a verdant Sahara teeming with life that stands in stark contrast to the arid desert the region has since become. Tassili paintings and engravings, like those of other rock art areas in the Sahara, are commonly divided into at least four chronological periods based on style and content. These are: an archaic tradition depicting wild animals whose antiquity is unknown but certainly goes back well before 4500 B.C.; a so-called bovidian tradition, which corresponds to the arrival of cattle in North Africa between 4500 and 4000 B.C.; a "horse" tradition, which corresponds to the appearance of horses in the North African archaeological record from about 2000 B.C. onward; and a "camel" tradition, which emerges around the time of Christ when these animals first appear in North Africa. Engravings of animals such as the extinct giant buffalo are among the earliest works, followed later by paintings in which color is used to depict humans and animals with striking naturalism. In the last period, chariots, shields, and camels appear in the rock paintings. Although close to the Iberian Peninsula, it is currently believed that the rock art of Algeria and Tassili developed independently of that in Europe.
While these traditions are successive, it does appear that earlier ones continued on for varying lengths of time after the appearance of later ones. Two important qualifiers need to be made. First, many scholars have recently questioned a pan-Saharan chronology and there is a move away from grandiose chronological schemes to concentrating more on understanding regional chronological variability. Second, the Sahara, given its vast size and various political complications, is still an inadequately researched area in terms of rock art and very few dates exist. As more work is done and techniques for dating advance, it is likely that this four-period dating scheme will be modified in particular regions and that more will be learned about the origins and demise of Saharan rock art.