Chad. Ennedi rock art.In the Manda guili shelter located on a steep wall; the red ochre paintings have retained all their brightness; well protected from erosion and alteration caused by wind and sun. A human is milking a big cow with big white spots on her dress. This painting testifies to the progressive drying leading just before our era to today's desert. Beef have been known in the Sahara for at least 6;000 years before disappearing 2;000 years ago.