Wet phases in the Sahara/Sahel region and human migration patterns in North AfricaIsla S. Castañedaa,1, Stefan Mulitzab, Enno Schefußb, Raquel A. Lopes dos Santosa, Jaap S. Sinninghe Damstéa and Stefan Schoutena
Edited by Thure E. Cerling, University of Utah, Salt Lake City, UT, and approved October 1, 2009 (received for review May 25, 2009)
The carbon isotopic composition of individual plant leaf waxes (a proxy for C3 vs. C4 vegetation) in a marine sediment core collected from beneath the plume of Sahara-derived dust in northwest Africa reveals three periods during the past 192,000 years when the central Sahara/Sahel contained C3 plants (likely trees), indicating substantially wetter conditions than at present. Our data suggest that variability in the strength of Atlantic meridional overturning circulation (AMOC) is a main control on vegetation distribution in central North Africa, and we note expansions of C3 vegetation during the African Humid Period (early Holocene) and within Marine Isotope Stage (MIS) 3 (≈50–45 ka) and MIS 5 (≈120–110 ka). The wet periods within MIS 3 and 5 coincide with major human migration events out of sub-Saharan Africa. Our results thus suggest that changes in AMOC influenced North African climate and, at times, contributed to amenable conditions in the central Sahara/Sahel, allowing humans to cross this otherwise inhospitable region.
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Link to abstract: http://www.pnas.org/content/early/2009/11/11/0905771106.abstract
Link to free, full, open-access article: http://www.pnas.org/content/early/2009/11/11/0905771106.full.pdf+html