When the Sahara was green (VI)The Sahara has not been always the most impressive desert in the world. Instead of this kingdom of rocks and sand, desolated and arid, existed in remote times a verdant and populated region. This is the testimony of the civilizations that flourished on the Central Sahara, civilizations that were extinguished when the wind of the desert covered the greenery with a shroud of sand.
Archaeology in the SaharaSouth of Tassili-n-Ajjer, on both sides of the Air massif, the great basins of the neolithic river Tafassasset, which lead into the Lake Chad, and the Timersoi, tributary of the Niger river, exist abundant vestiges of habitats of herders that also practiced fishing. Specially in the basin of the Tamersoi it is common to find fish spines, mollusc shells and crocodile bones, besides bone harpoons and net weights, which demonstrated the practice of fishing with dragnet. It is probable that the southern part of the Sahara, south of the Tropic of Cancer, were wetter than the northern part and that life would endure more time in there. The examination of the sites shows a great poverty of aquatic fauna north of the Ahaggar. As Theodore Monod said, while the traveler crossed the vast desertic depressions in Mauritania, known as djouf in the old maps, he will walk above a continuous carpet of silex arrowheads along kilometers and kilometers. In the cliffs at Tichitt-Oualata the density of neolithic habitats was high. The region of Tichitt includes more than hundred neolithic villages solidly built, which is excepcional. It seems that the population of the Sahara must have been quite considerable in those times, specially during the fourth millenium before the Christian Era. It has been always supposed that Africa is the cradle of mankind, and the Sahara would not be an exception. In northern Chad were discovered the remains of an australopithecus from a million and a half years, and remains of very primitive industries, of carved peebles, which indicated that the area was populated since the beginning of mankind.
From the forest to the desertWhat produced the desiccation of the Sahara? The ice melt in Europe could have provoked the alteration of the regime of atmospheric pressures, contributing to move away from the Sahara the clouds that previously discharged over it. If, on the other hand, the winterly rainfall from the polar cold front, irrigated almost all the Sahara and were relieved by the summery monsoon, this regime of rainfall was degraded to the point that an irreversible imbalance between the coefficient of evaporation and rainfall was introduced. Around 6000 BC the Lake chad covered a great surface and rivers such as the Tafassasset, Timersoi, Tilemsi and Tamanrasset discoursed regularly, irrigating the area and favouring the vegetation. The highlands of the Ahaggar, Tassili-n-Ajjer and Tibesti benefited from a mediterranean climate. It is known that pines, cypresses, cedars, ashes, oaks, hackberries, walnuts, alders, myrtles, limes and olives grew there, reaching the neighboring plains.
The first neolithic dwellers arrived to the Tropic of Cancer from the south, being replaced around 4000 BC by the bovid herders that came from the east. From 2500 BC onwards the mediterranean flora started to experiment a certain drawback; tropical species replaced it in the valleys and slowly in the plateaus as well. From this period onwards the desertification will advance to the last consequences. If the climatic variations gave rise to a decreasing in the rainfall, it is possible that the multitude of domesticated animal species would produce a strong pasturage that depleted the vegetation, a phenomenon that could be observed in the Sahel, still in the 20th century. It is probable as well that the primitive forests were destroyed to create pasturage areas. So, century after century, the forest turned into savannah, the savannah turned into steppe, and the steppe turned into desert. The presence of hippopotamus is proved up to the 2000 BC; later there is no trail of them. The same applies to rhinoceros and giraffes, that slowly disappeared from the topics of the rock paintings. When the equestrian peoples arrived to the Central Sahara, the herders departed to the south; the artistic style of the newcomers is so different from the one of the herders, that there is not supposition of a cultural contact between them. The peoples of the chariot and the horse practiced the herding as well, but in a lesser extent; the mastering of transport allowed them to trade with far lands. Desertification continued and at the beginning of the Christian Era the Sahara the desertification was already definitive: the ergs were formed and the rainfall turned progressively more irregular.
This is one of the most ancient depictions of the cultivated date palm, dated around 1000 BC. The pruning of the old palms and the cleaning of the trunks with a sickle indicate the practice of cultivation. The green, lush Sahara was already a memory of the past.
Depiction of a chariot in the refuge of Tin-n-Anneuin, near the Algeria-Libya border, painted around 1000 BC. The chariot is towed by two horses and the frame possesses excepcionally two rods. The chariots were used for fighting and hunting.
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