Timing and causes of North African wet phases during the last glacial period and implications for modern human migration.
We present the first speleothem-derived central North Africa rainfall record for the last glacial period. The record reveals three main wet periods at 65-61 ka, 52.5-50.5 ka and 37.5-33 ka that lead obliquity maxima and precession minima. We find additional minor wet episodes that are synchronous with Greenland interstadials. Our results demonstrate that sub-tropical hydrology is forced by both orbital cyclicity and North Atlantic moisture sources. The record shows that after the end of a Saharan wet phase around 70 ka ago, North Africa continued to intermittently receive substantially more rainfall than today, resulting in favourable environmental conditions for modern human expansion. The encounter and subsequent mixture of Neanderthals and modern humans - which, on genetic evidence, is considered to have occurred between 60 and 50 ka - occurred synchronously with the wet phase between 52.5 and 50.5 ka. Based on genetic evidence the dispersal of modern humans into Eurasia started less than 55 ka ago. This may have been initiated by dry conditions that prevailed in North Africa after 50.5 ka. The timing of a migration reversal of modern humans from Eurasia into North Africa is suggested to be coincident with the wet period between 37.5 and 33 ka.
Max Planck Institute for Evolutionary Anthropology, Department of Human Evolution, Deutscher Platz 6, 04103 Leipzig, Germany.|Bristol Isotope Group, School of Geographical Sciences, University of Bristol, University Rd, Bristol, BS8 1SS, UK.
Dirk L
DL
Hoffmann
Department of Geography, Environment and Earth Sciences, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
Mike
M
Rogerson
Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria.
Christoph
C
Spötl
Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria.|Austrian Academy of Sciences, IGF, Technikerstr. 21a, 6020 Innsbruck, Austria.
Marc
M
Luetscher
Institute for Mineralogy and Petrology, Department of Earth Sciences, ETH Zürich, Clausiusstr. 25, 8092 Zürich, Switzerland.
Derek
D
Vance
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, 24148 Kiel, Germany.
Anne H
AH
Osborne
National Oil Corporation (NOC), Exploration Department, P. O. Box 2655, Tripoli, Libya.
Nuri M
NM
Fello
Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria.
Gina E
GE
Moseley
D000352:Africa, Northern; D002980:Climate; D004641:Emigration and Immigration; D019015:Geologic Sediments / Q000032:analysis*; D049690:History, Ancient; D006801:Humans