THERE is abundant evidence that early in the Quaternary age the Sahara was inhabited by man and that desiccation has since been proceeding. In so far as this process is one of climatic change, it is beyond the control of man ; but there is also much evidence that the increase of desert conditions in both north and south is largely due to human interference. In a pamphlet entitled "The Threat of the Sahara", reprinted from the Journal of the Royal African Society, Prof. E. P. Stebbing reviews the available evidence of progressive desiccation and discusses the causes. These can be summarized as war, primitive methods of agriculture, excessive grazing and pasturage and fire. Intertribal warfare has laid waste great tracts and so promoted soil erosion. The method of shifting cultivation, entailing the cutting down of successive areas of forest and their abandonment when annual burning produces too poor a supply of fertilizing wood ash, has allowed the spread of scrub land. This degraded forest is given over to pasturage which tends to destroy the vegetation, the last stage in its use being the pasturing of goats. Prof. Stebbing sees little evidence that the desiccation can be attributed to climatic oscillations, and is extremely doubtful that the succession of a wet period will reverse the present trend.