The vast Sahara Desert, which stretches across North Africa, began to form in the late Miocene and early Pliocene, some 10 million years ago (MYA). South of this geophysical region, gorillas diverged from the hominid line about 9 MYA and chimpanzees followed 7 MYA. By 4.5 MYA, Australopithecus appeared in the Rift Valley of East Africa and, by 2 MYA, Homo erectus had evolved.
While the Sahara may have been a natural blockade to the northward migration of the earliest hominids, the Pleistocene Epoch (2 MYA to 10,000 YA) brought wide swings in the global climate, marked by four periods of glaciation. During these glacial periods, a cool, wet climate caused the Sahara to contract, opening corridors of savannah that likely permitted ancestral hominids to migrate northward, into Eurasia. Following earlier migrations of Homo erectus, Neandertals began to leave Africa about the time that humans were first appearing, some 150,000 years ago, and occupied Europe by 100,000 years ago. Man remained in sub-Saharan Africa until about 60,000 years ago, when the Wisconsin glaciation permitted migration through northeastern Africa and, due to lowered sea levels, directly across the Red Sea to the Arabian Peninsula.
Nomadic human tribes likely entered parts of the Sahara Desert from the earliest days or our existence but extensive exploration and settlement of that harsh landscape would not occur until the Holocene, aided by the domestication of goats (10,000 YA), sheep (9000 YA), cattle (8000 YA) and dromedary camels (4000 YA). Even today, most human settlements lie in fringe regions of the Sahara and interior towns are limited to natural oases, the Nile Valley and volcanic highlands.
