Getting Out of Africa: Sea crossings, land crossings and culture in the hominin migrations

Palaeoanthropologists and archaeologists have advanced a wide range of explanatory narratives for the various movements of Homo erectus/Homo ergaster, and the first modern Homo sapiens, Out of Africa-or even back again. The application of Occam's razor-a parsimonious approach to causes-gives a more cautious approach. There is nothing in the available evidence that would require the ability for a human water crossing from Africa before the later Pleistocene, whether across the Strait of Gibraltar, the Sicilian Channel or the southern Red Sea (Bab el-Mandab). A parsimonious narrative is consistent with movements across the Sinai peninsula. The continuous and zone from northern Africa to western Asia allowed both occupation and transit during wet phases of the Pleistocene; there is no requirement for a sponge model of absorption followed by expulsion of human groups. The Nile Valley as a possible transit route from East Africa has a geological chronology that could fit well much current evidence for the timing of human migration. The limited spatial and temporal opportunities for movements Out of Africa, or back again, also puts particular difficulties in the way of the gene flow required for the multiregional hypothesis of the development of modern Homo sapiens.