A climate history painted on rock
The Tassili n'Ajjer is a vast sandstone plateau in southeastern Algeria, covering 72,000 square kilometers of what is now hyper-arid desert. Its name translates to "Plateau of the Rivers," a title that hints at a dramatically different past. The more than 15,000 paintings and engravings found here are one of the world's important collections of prehistoric art. They record the African Humid Period, a time from roughly 14,500 to 5,500 years ago when Earth's orbital precession warmed the northern hemisphere, strengthening the West African Monsoon and turning the Sahara into a savanna.
The art creates a timeline of this climate transformation. The oldest works, from the "Large Wild Fauna" period (around 12,000 to 6,000 BC), show a landscape filled with water-dependent animals. Engravings depict hippos, crocodiles, elephants, and an extinct species of giant buffalo, Bubalus antiquus. This imagery confirms a once-lush environment with rivers and lakes capable of supporting large herds and aquatic life. As the climate began to dry around 6,000 years ago, the art reflects a shift in fauna and human society.
From hunter-gatherers to camel caravans
Archaeologists have classified the art into several distinct phases that track environmental and cultural changes. Following the early period of wild fauna, the "Round Head" period (approx. 9,500 to 7,000 years ago) has large, enigmatic humanoid figures, sometimes with featureless round heads or apparent masks. One of the most famous figures is the "Great God of Sefar," a ten-foot-tall being with strange appendages that some interpret as a shaman or deity.
The subsequent "Pastoral" or "Bovidian" period (starting around 4,500 BC) documents the arrival of domesticated cattle. The art from this time is highly naturalistic, with detailed scenes of herding, milking, and daily life among cattle-herding societies. As aridity increased, the "Horse" period began around 2,000 BC, marked by depictions of horses pulling chariots. It is unlikely chariots were actually driven across the rocky plateau; these images may be symbolic. The final phase is the "Camel" period, which started within the last 2,000 years. The appearance of the dromedary camel shows the full establishment of the desert conditions that persist today. The art was first brought to widespread international attention by French archaeologist Henri Lhote in the 1950s, though his methods—which included wetting the paintings for photography—are now known to have caused damage to the art.