A climate history written on stone
More than 15,000 paintings and engravings at Tassili n'Ajjer record a dramatically different Sahara. The images chronicle a 10,000-year environmental history, showing how the region transitioned from a temperate savanna to the arid desert it is today. The oldest works belong to what archaeologists call the "Large Wild Fauna Period," beginning around 12,000 years ago, and feature engravings of animals like the now-extinct giant buffalo (Bubalus antiquus), elephants, rhinos, and giraffes.
The famous "swimmers" belong to the subsequent "Round Head" period, dated from approximately 9,500 to 7,000 years ago. These paintings provide direct evidence of the African Humid Period (AHP), a phase that began around 14,500 years ago when changes in the Earth's orbit intensified the African monsoon, bringing extensive rainfall to Northern Africa. This era turned the Sahara into a network of lakes, rivers and wetlands that supported a diverse ecosystem, including hippos and crocodiles, which are frequently depicted in the art. Scientific analysis of ancient lake bed sediments and pollen confirms this greener past.
The art and its creators
The artists of the Round Head period used the smooth walls of the region's eroded sandstone rock shelters as their canvas. The sandstone geology of the 72,000-square-kilometer plateau created a landscape of "rock forests," canyons and natural arches that provided shelter. The painters created their pigments from locally sourced minerals. Red and yellow colors came from ochre (hematite and limonite), while black was derived from charcoal or manganese oxides. These pigments were likely mixed with a binder like egg yolk, animal blood, or plant juices before being applied with fingers or rudimentary brushes.
The swimming figures themselves are portrayed with elongated bodies and the characteristic round, featureless heads that give the artistic period its name. They are shown in poses, appearing to float or move through water. This style is unique to the Central Sahara and represents a symbolic culture of hunter-gatherers who thrived in the once-fertile environment. As the climate began to dry around 6,000 years ago, the art style shifted to the "Pastoral Period," which is dominated by scenes of domesticated cattle, reflecting a major change in the lifestyle of the region's inhabitants.