WETLANDS, LAKES, AND RIVERS: WATER BODIES AS CORRIDORS FOR AND BARRIERS TO MIGRATION THROUGH NORTH AFRICA DURING THE LATE QUATERNARY

Numerous paleoenvironmental studies in North Africa have documented the existence or expansion of rivers, lakes (both fresh and saline), and wetlands during humid climatic intervals throughout the Pleistocene. While the shift from arid/hyperarid to more humid conditions would generally be presumed to make the region as a whole more conducive to occupation and migration, an assumption supported by the frequent association of lithic artifacts with water-lain sediments, certain components of the landscape could actually become less hospitable to through travel or habitation with increasing rainfall. During humid phases, the Nile Valley may have been choked with thick vegetation (Kleindienst, 2000) and disease-ridden; or, a mosaic of spring fed ponds and connecting channels present in oases during relatively arid times may have expanded into an extensive, impassible swamp. Thus while potential for migration would have increased through the region as a whole under enhanced rainfall relative to today, core regions suited for occupation may have shifted rather than simply expanded, leading to different predicted migration paths over time.

An additional consideration regarding the environmental context for migration through North Africa is the synchrony (or lack thereof) in humid conditions across the region. Compilations of dates on fluvial, lacustrine, and palustrine sediments across North Africa, though hampered by the considerable errors (i.e., > 5-10 ka) often associated with U-series, OSL, TL, and ESR geochronology, suggests significant east-west and/or north-south variability in the onset and cessation of humid conditions. This would allow for some accommodation of changing environments through intra-regional migration. Differing seasonality of rainfall (i.e. winter vs. summer rains) on the northern and southern margins of habitable North Africa during humid phases may have impeded cross-regional movement by requiring populations to adapt to a new seasonal resource base.

Kleindienst, M.R., 2000, On the Nile Corridor and the Out of Africa Model: Current Anthropology, v. 41, p. 107-109