Middle Stone Age Sites from Eritrean Red Sea Coast: Perspectives on Origin and Dispersal of Modern Humans
Africa´s position as the origin of modern humanity is widely accepted, with fossil and archaeological finds from different parts of the continent demonstrating such events. The Middle Stone Age holds a special place in the study of human evolution because it was during this cultural phase that the first anatomically modern humans are believed to have emerged in Sub- Saharan Africa between 200,000 and 150,000 years ago. Their subsequent dispersal to other parts of the world is also believed to have occurred during the Middle Stone Age and is thus partly understood in light of technological and cultural traits of this phase discovered in the African and Eurasian landmasses.
Similarly, the origins and dispersals of early modern humans within and outside of Africa were shaped by changes in global climate that oscillated in terms of repeated glacial and interglacial events that featured during the Late Pleistocene (200,000-10,000 years ago). These climatic fluctuations as will be demonstrated here were significant for the evolution of the biological and behavioral traits of the human lineage.
Apparently, the patterns of human ancestry as understood from genetics are at present producing models of human migration, which need to be tested with independent lines of fossil and artifact evidence. In this respect, it becomes important to frame the presumed dispersals of early modern humans within two major events that occurred between 130,000- 100,000 and 80,000- 60,000 years ago respectively. As far as the dispersals are concerned, two routes have been considered, namely the Northern Route, (which included the Nile- Sinai pathway) and the Southern Route (which involved the southern Red Sea).
The geographic position of the Red Sea, therefore, makes it an important place in the context of current debate on human origins and dispersal hypotheses. The Bab al Mandab Strait at the southern end of the Red Sea has been proposed as a credible gate through which prehistoric maritime connections were possible between Africa and the Arabian Peninsula. Environmental models show the water barrier between Africa and southern Arabia can be narrowed to less than 10 km during major glacial events. As have been postulated recently, the coastal margins of both the African and Arabian sides of the Red Sea coasts must have been inhabited by early humans who used the Bab al Mandab to enter the Arabian Peninsula. In this respect, it will be significant to correlate cultural similarities between African and Western Arabian Middle Stone Age entities to collect evidence for early human contacts via the Strait of Bab-al Mandab.
By virtue of its strategic geographic position along the African side of the Red Sea, Eritrea represents a model to look for Stone Age Sites associated with Late Pleistocene human dispersals out of Africa. Archaeological investigations at Abdur and Asfet localities in the Red Sea Coast of Eritrea recently have provided cultural and ecological contexts for these Middle Stone Age human adaptations along the Eritrean Coast. Drawing on evidence from the Eritrean Red Sea Coast, a summarized account is provided here by pinpointing the importance of these sites to understand the dispersal of early modern humans from Africa to the Arabian Peninsula and eventually to other parts of Eurasia.
Putting Abdur and Asfet in Context
Stone tools within the emerged reef terraces on the western shoreline of the Buri Peninsula, Red Sea coast of Eritrea, were discovered in late 1990s and were dated to 125,000 years ago. These artifacts are the earliest well-dated evidence for human occupation of coastal marine environments. The Abdur Archaeological site is found approximately 60 km southeast of the port town of Massawa, along the eastern peripheries of the Gulf of Zula. The Abdur finds comprised two settlement scenarios represented by bifacial belonging to the Achuelian tradition in one hand, and Middle Stone Age obsidian stone tools on the other. Large land mammals and marine invertebrates were also found in close association with these artifacts. The marine terrace belongs to Pleistocene events and stone tools were found embedded within the reef limestone further implying that early modern humans were adapted to the Eritrean Red Sea Coast by exploiting marine food resources. This trend signifies behavioral changes in resource exploitation and feeding habits of early modern humans, who needed to respond to climatic stresses of the respective interglacial period. Early humans who were forced to move from terrestrial habitats (around lakes and rivers) during this time should have settled along the coast in response to diminishing water resources further in land in the Denakil Depression and the eastern escarpments. These early human adaptation strategies that were induced by climatic fluctuations in turn must have enabled early modern humans to use the shores as routes for their dispersal out of Africa and migration along the shorelines of Arabia into Southeast Asia during the lowering of the sea level.
The evidence from Abdur in Eritrea, together with the proof of coastal occupations at Klasies River Mouth in South Africa (dated to 116,000 years ago) indicate that early humans were well adapted to utilize marine foods by the last interglacial period evinced during the Late Pleistocene(200,000-10,000 years ago). Accordingly, uplifted marine terraces, similar to those around Abdur, along the Eritrean coast could be important geological contexts for the study of human evolution and behavior.
Further studies along the Eritrean Coast in 2005-2006 have likewise yielded evidence of Middle Stone Age at the site of Asfet, few kilometers outside the Abdur proximities. Located on the southwestern edge of the Gulf of Zula, approximately 800 meters from the present coastline, the Asfet finds further broaden the character of the Middle Stone Age human adaptation on the African Coast.
It is now agreed that some East African populations initiated an eastward dispersal into the Arabian Peninsula through the southern Red Sea route with the beginning of a glacial event between 72,000 and 62,000 years ago. These movements which were driven as the northward movement from East Africa to Southwest Asia were halted due to severe conditions in the Sahara desert. This event is further demonstrated by genetic data which affirms that a genetically distinct human lineage migrated from east Africa into Arabia through the southern Red Sea corridor sometime between 80,000 to 65,000 years ago. The Asfet finds, which comprise typical Middle Stone Age artifacts, have compelled researchers to assert that the makers of the Asfet assemblage must belong to the Homo Sapiens fossil remains discovered from Middle Stone Age sites in North East Africa.
Furthermore, recent archaeological investigations in southern and eastern Arabia have reported stone tools that resemble North eastern and Nile Valley Middle Stone Age complexes. Such similarities have suggested to researchers a major phase of human expansion into Arabia during this period and the Asfet finds show resemblance with the archaeological remains from the Nile valley and Arabian Peninsula to suggest to researchers a major phase of human conquest of Arabia during this period. Putting things into perspective, therefore, the Asfet site could represent part of a widespread coastal adaptation by early modern humans along the African side of the Red Sea before their subsequent dispersal to Eurasia. In other words, we can conclude that early modern humans who successfully inhabited the Buri-Zula plains during this time may have launched southward movements along the Danakil- Djiboutian coast, thereby entering Southern Arabia via Bab al Mandab. It will be equally reasonable to postulate that they could have dispersed northward to southwestern Asia along the Sudanese-Egyptian Red Sea environs. In conclusion, with current debates on dispersal of early modern humans firmly established around the Red Sea basin, the evidence from Abdur and Asfet in Eritrea seize a significant place to understand the behavioral and cultural traits of our immediate human ancestry coupled with evidence of climatic records of the Late Pleistocene in Eritrea. Future research along the Eritrean coast shall also help to fully comprehend these major events.