Human Migrations in Prehistory - the Cultural Record
Ofer Bar-Yosef
Abstract
Until the invention of airplanes human migrations took two routes – terrestrial and maritime. There is no doubt that the first was the earliest and most common way, while crossing waterways is evident in the remains from the Upper Pleistocene but could have happened accidentally at earlier times. Colonization of new regions by humans could have been successful or doomed to failure. In the first case long archaeological sequences are expected and in the second scenario – chronological gaps mark the regional histories.
The first terrestrial migration "out of Africa" occurred when Homo ergaster made its way to Eurasia, stopping in Dmanisi (ca.1.7 Ma). Homo ergaster probably moved through the Nile Valley into the Levant, across Eastern Anatolia, or the Zagros mountains. An unresolved issue is 'why hominins left Africa'. One potential answer is the relatively small 'homeland' of Pliocene hominins and its ecological conditions. Among the limiting factors were the zoonotic and other diseases that infest the rain forest and the deserts. In addition, incidental attraction to new areas, in particular those of the Ethiopian highlands and beyond, could have played an important role in the decision to move northward.
The bearers of the Acheulian tradition, the makers of handaxes, were the migrants of the second wave. These artifacts are known from 'Ubeidiya (ca.1.4-1.2 Ma), in the Jordan valley, and many sites in the Levant, eastern Anatolia , Iran and the Indian sub-continent. While the 'Movius Line' is still considered the boundary between those who used flake and core stone tools and the makers of the Acheulian handaxes, several crossings were recorded (e.g., Bose in south China). However, this type of artifact is missing during the early Middle Pleistocene from eastern Europe and most of central Asia and north-eastern Asia. At the other edge, in western Europe, the Acheulian could have been the result of crossing the Gibraltar at ca. 0.7-0.6. Ma.
A possible third wave of migrants, perhaps of only small isolated groups, is indicated by the Acheulian stone tools with numerous cleavers discovered in Gesher Benot Ya'aqov (ca. 0.8 Ma) in the Jordan Valley. These newcomers employed the route along the Red Sea into the Levant and perhaps into southern Asia.
The following movement of humans "out of Africa" and into the Levant involved the archaic Modern humans represented in the skulls of Omo-Kibish and Herto in Ethiopia and the Skhul-Qafzeh group in the Levant. These date from ca. 200-90,000 years ago and were the bearers of Mousterian tool assemblages (also known as Middle Stone Age in East Africa). There is no evidence as yet that they succeeded to move into western Eurasia before the Last Interglacial.
The earliest Mousterian industry is rich in blades and elongated points and known from Mt. Carmel and the Galilee (Israel), as well as from the El-Kowm basin (Syria),from several sites in the Caucasus (labelled as the Djrujulan industry in Georgia) and in Obi-Rahmat cave (Uzbekistan). Hence, it is not impossible that these groups, with an eastern orientation, avoided the Neanderthal territories in the west. We may assume that the archaic Modern humans were the ancestors of the later population that is generally considered as the creators of the Upper Paleolithic "paleo-cultures".
The most famous migration is that of Modern humans groups who spread from sub-Saharan Africa (according to the genetic evidence) into Eurasia and probably into South Africa. Their "paleo-cultures" are reasonably well-documented in the archaeological sequence from the Nile Valley and the Levant. The migrating groups carried the late bladey Nile Mousterian tool-kits, and slightly modified them to become what we call the "Initial Upper Paleolithic" in the Levant (once known as the "Transitional Industries"), sometime around 50,000 years ago.
The southern route across Bab el Mandeb straits, through the southern Arabian peninsula, into the Indian subcontinent and from there to New-Guinea and Australia during the Last Glacial times, is archaeologically poorly known. The best evidence for this migration comes only from the final stop in Australia and Tasmania. Moving there required a crossing of a waterway of some 80-100 km. It would be therefore difficult to deny that other parts of this long route were not done by coastal navigation.
Finally, there is little doubt now that North America was colonized by coastal navigation. The finding that the American gourd came from eastern Asia is an important indication. This does not detract from the possible terrestrial colonization of the northern latitudes through Beringia.
Finally, we need to consider several difficulties or ambiguities involved in the research of prehistoric periods and in particular concerning past human migrations.
The epistemological question of "how do we know what we know in the archaeology of human migrations"? is only answered by employing the historical records concerning dispersals of human groups as a reference collection. Cases such as the Norse occupation of Greenland can serve as an example for success and failure of human groups to adapt to a specific environment and climatic changes. Similarly, the colonization of the Pacific islands provides ample evidence including the genetic information.
In addition, the correlation between the identified stone artifacts and human populations is often a subject for disagreements among prehistorians. Needless to say that we have no "time machine" to check the identity of the tool makers in the remote past. However, several examples such as demonstrated by the Magdalenian "paleo-culture" may lend support to current interpretations. Magdalenian stone tool-kits and art objects (19-14,000 cal B.P.) across most of western and central Europe testify to the presence of the same cosmology, same tool making techniques, and most probably for the use of the same language among a large and successful population of foragers. They spread from their original homeland in the Franco-Cantabrian region and became a testimony to an expanding population of foragers.
In sum, active research, in spite of many unknowns and gaps in our knowledge concerning the prehistoric past, provides ample evidence to speculate about past human behaviours.
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