Out of Africa, but how and when? The case of hamadryas baboons (Papio hamadryas).

Many species of Arabian mammals are considered to be of Afrotropical origin and for most of them the Red Sea has constituted an obstacle for dispersal since the Miocene–Pliocene transition. There are two possible routes, the ‘northern’ and the ‘southern’, for terrestrial mammals (including humans) to move between Africa and Arabia. The ‘northern route’, crossing the Sinai Peninsula, is confirmed for several taxa by an extensive fossil record, especially from northern Egypt and the Levant, whereas the ‘southern route’, across the Bab-el-Mandab Strait, which links the Red Sea with the Gulf of Aden, is more controversial, although post-Pliocene terrestrial crossings of the Red Sea might have been possible during glacial maxima when sea levels were low.