Research on the mobility of the Palaeolithic and Neolithic societies and on cultural changes in Africa often uses deterministic arguments, which put forward the role of climatic changes, in particular the abrupt dry events that have characterized the Pleistocene, with the final cycle of increasing aridity that lead to the end of the green Sahara in the mid-Holocene. Meanwhile, applied models take into account only a part of the continent: West Africa is usually under-represented, suggesting that it had no interaction with the other regions. Most probably, such a misleading assumption of a minimal role of West Africa is not based on a long analysis of data. The obvious reason is that West Africa suffers from a lack of both archaeological and palaeoenvironmental researches. Very few Palaeolithic or Neolithic sites are firmly dated and most of the palaeoenvironmental data rely on marine or lacustrine cores, whose relevance at the regional scale for the studied period remains disputable.
Meanwhile, preliminary research conducted in the Falémé Valley, East of Senegal, have shown the potential of this region for allowing joint studies on both new Palaeolithic/Neolithic data and local palaeoenvironmental data. The stratigraphic record in the valley is indeed well preserved, though complex, and preliminary dates (OSL and radiocarbon) show that it covers the whole Upper Pleistocene and Holocene. Silts deposits alternate with coarse channel deposits and the palaeoclimatic significance of this structure needs to be understood. In particular, the sedimentary records attributed to Marine Isotope Stage 2 (MIS2, 24-12 ka), partly contemporaneous with the arid Ogolian (20-12 ka), are well developed and will allow refined studies on this period. Archaeological assemblages are present on the whole stratigraphic sequence and more particularly in the levels with a preliminary MIS2 age. This is important as MIS2 archaeology is very poorly known south of the Sahara: at that time human populations apparently suddenly disappeared, either decimated by the drought, or gathered in hypothetically more favorable refugia.
Our project aims thus at performing joint archaeological, palaeoenvironmental and geochronological (OSL and C14) studies on a section (>100 km long) of the Falémé Valley in order to:
- Establish of a new chrono-cultural framework for the end of the Pleistocene and Early/Middle Holocene in West Africa. When completed this will be compared to the one established at Ounjougou (Mali), 950 km further to the North-East, in a currently drier environment;
- Track the climatic and environmental changes on the last 70 ka at least. In particular, we will try to understand how the Heinrich events at the end of the Pleistocene and the various droughts of the Early and Middle Holocene have impacted the environment of the valley (i.e., rain, hydrology, aeolian inputs, vegetation) and how they have eventually impacted the human populations (i.e., mobility, technical and cultural changes).
Our project, scheduled for 3 years, will rely on the complementary skills of four teams, 2 French and 2 Swiss, that form the consortium, in collaboration with the IFAN (University of Dakar, Senegal): the IRAMAT-CRP2A (CNRS-University Bordeaux-Montaigne, France) in charge of OSL dating, the LGP (CNRS-University Paris-Est Créteil, France) that will realize the palaeoenvironmental studies, the APA (University of Geneva, Switzerland), that will hold the archaeological task, and the IBP (ETH Zurich), will perform radiocarbon dating. The budget comprises 390 k€ HT for the French teams and 468 k€ HT for the Swiss ones.