![]() The earliest inhabitants of central North Africa have left behind significant remains: early remnants of hominid occupation in North Africa, for example, were found in Ain el Hanech, in Setif (c. This separates populations of some of the species in areas with different climates, forcing them to adapt, possibly giving rise to allopatric speciation. Following inter-pluvial arid periods, the Sahara area then reverts to desert conditions and the flora and fauna are forced to retreat northwards to the Atlas Mountains, southwards into West Africa, or eastwards into the Nile Valley. During periods of a wet or " Green Sahara", the Sahara becomes a savanna grassland and various flora and fauna become more common. These conditions are responsible for what has been called the Sahara pump theory. The Sahara is presently as dry as it was about 13,000 years ago. By around 4200 BCE, however, the monsoon retreated south to approximately where it is today, leading to the gradual desertification of the Sahara. In the southern Sahara, the drying trend was initially counteracted by the monsoon, which brought rain further north than it does today. Once the ice sheets were gone, the northern Sahara dried out. The end of the glacial period brought more rain to the Sahara, from about 8000 BCE to 6000 BCE, perhaps because of low pressure areas over the collapsing ice sheets to the north. ![]() At present (2000 CE), we are in a dry period, but it is expected that the Sahara will become green again in 15,000 years (17,000 CE).ĭuring the last glacial period, the Sahara was much larger than it is today, extending south beyond its current boundaries. This is due to a 41,000-year Axial tilt cycle in which the tilt of the earth changes between 22° and 24.5°. Human habitation in North Africa has been greatly influenced by the climate of the Sahara (currently the world's largest warm desert), which has undergone enormous variations between wet and dry over the last few hundred thousand years.
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