Hominid Migration Routes Out of Africa: Southern Arabia
The Sinai region of northeast Africa is widely thought to have provided the singular route of hominid migrations out of Africa. Fluctuating sea levels and the changing position of the African and Arabian plates during the Plio-Pleistocene, however, may have allowed for the terrestrial exchange of hominids between East Africa and southwest Arabia as well. This proposition is supported by claims for the recovery of pre-Acheulian lithic tools from Yemen.
Schematic diagram of the relationship between geological plates of the African and Eurasian continents. The reconstructed rotation of plates through time and other evidence indicate a solid land-bridge between East Africa and southern Arabia until the early Pliocene (ca. 4 million years ago).
A director of ACS (Gregory F. Walwer) conducted a driving and pedestrian survey in various major drainages of southern Yemen. The survey was complemented by inspections of lithic assemblages from the four national museums of Yemen. While the veracity of some items representing early lithic tools remains questionable, others are clearly products of intentional lithic reduction that typologically resemble those recovered from early hominid sites in East Africa. The contemporaneity of the Yemeni and East African assemblages, however, has yet to be established as most of the Arabian material has been recovered from surface contexts or undated stratified settings. In addition, many regions east of the "Movius Line" contain chopper-like industries dating to the Late Pleistocene.
Oxygen isotope curves indicate fluctuating sea levels through time. When correlated with the inferred geological spread of the Bab el Mandeb Strait that now separates East Africa from southern Arabia, it appears that there may have been many episodes of intermittent connections between the two plates which would have afforded an opportunity for alternative hominid migration routes out of Africa.
In support of possible early migrations between East Africa and southwest Yemen, paleogeographic and paleoecological reconstructions indicate considerable continuity between the two regions through time, more so than that between East Africa and the Levant. In addition, a correlation between changing sea levels and the estimated changing depth of the intervening Bab el Mandeb Strait indicates several periods which would have presented possible land bridges between the African and Arabian plates. The results of this study raise serious questions about the possibility for alternative migration routes out of Africa which have a bearing on current interpretations of hominid evolution.