THE CLIMATIC BACKGROUND: THE DESICCATION OF THE SAHARA

Today all authorities agree that the Sahara had a humid climate during the six to eight millennia prior to about 2000 BC. Great lakes like the modern Lake Chad covered much of the southern Sahara. These have left evidence of their presence in the form of deposits of diatoms (which can provide radiocarbon dates); the skeletons of reptiles, mammals and fish; and waterside human habitation sites possessed of rich Stone Age industries. The largest of these lakes, ‘Mega-Chad’, then extended over 330,000 sq. km to the 325 m contour, whereas the modern lake has an area of only 25,000 sq. km, and is bounded by the 282-metre contour. The latter it should be noted, is not at the lowest point of the Chad basin, which in Djourab is only 165 m above sea level.

In these favourable conditions, a wide variety of fauna were able to live in areas which are today wholly desert, such as Tenere, Tanezrouft and Majabet al-Koubra. Innumerable neolithic sites have been found and, moreover, most of those rocks which are suitable are covered with pictures of the large ‘Ethiopian’ fauna which could then live in the Sahara, including elephants, rhinoceroses, giraffes, antelopes and hippopotamuses. Saharan man was then a hunter-gatherer and sometimes also a fisherman.

From about 5000 BC, the Sahara began slowly to change into desert, a development which is probably connected with the general increase in temperatures in the northern hemisphere which led to the melting of the glaciers of northern Europe.