Slow apocalypse

The cattle herding was so successful that it spread south from the mountains. Speculation that the herdsmen invited the desert through overgrazing is unfair. Older and larger climatic forces were at work. Around 2000 B.C., the weather simply shifted. A dryness settled tentatively across the Saharan lowlands, and crept into the mountains, and slowly deepened. There were years then as now when the rains returned and the vegetation thickened. But the desert was on its way.

You might expect people not to have noticed such gradual impoverishment. But these people lived surrounded by their art, the now-ancestral celebrations of a bountiful land: etching scarred the rocks for hundreds of miles; paintings endured in theindelible burnt-orange of laterite and iron oxide. The old creations must have forced people to confront their loss. Did they fight each other, hunt witches, find new ways to pray? It made no difference anyway. The lakes and rivers shrank. The big wild animals drifted south. On a cliffside near Djanet, someone drew a weeping cow, which still looks like a declaration from the end of time.

— William Langewiesche