Successes and failures of the human dispersals from North Africa.

Under the Out-of-Africa scenario, various routes have been supposed for the exit of the African Homo sapiens. The Mediterranean coast of North Africa, the Sahara, the Nile Valley, the Red Sea coast, and the Bab el Mandab could have been corridors leading out of Africa. Even though data are still too scanty, heterogeneous, and patchy to support one hypothesis against the others, scholars have tended to search for “the” route out of Africa, as if one passageway would rule out possible others. However, a single-dispersal model may not be correct as early modern humans may have found different ways to leave their native lands. If North Africa can contribute to an understanding of the adaptational dynamics of modern human peopling and their radiation towards different parts of Eurasia, other regions, such as the Horn of Africa, may be contemplated as well. This paper focuses on the events that took place in North Africa. In this region, anatomically modern humans were not always successful once they departed from Africa and moved towards the temperate, and dry, latitudes of the eastern Mediterranean basin in the Levant. Two distinct movements have been recognised within the Out-of-Africa 2 model, one occurring between c. 130 and 80 ka BP, the other taking place after 50 ka BP. The two phenomena were separated by an abrupt climatic transition that affected the south-western Mediterranean basin during the transition from MIS 5a to MIS 4, around 74 ka BP. As these two events exhibit very distinct features and are divided by a long time span, it seems reasonable to refer to the first event as “Out of Africa 2a” and to the second one as “Out of Africa 2b”. During the first migration out of Africa, modern humans seem to have failed in the competition for resources against Neanderthals, whereas they succeeded in their second migration. The present paper examines some of the reasons of the failure of the Out-of-Africa-2a migration and, on the other hand, of the success of the Out-of-Africa-2b movement with particular attention to North Africa.