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International audienc

Bayon et al. (Reports, 9 March 2012, p. 1219) interpreted unusually high aluminum-potassium ratio values in an Atlantic sediment core as indicating anthropogenic deforestation around 2500 years before the present (B.P.). We argue that there is no terrestrial evidence for forest destruction by humans and that the third millennium B.P. rainforest crisis can be clearly attributed mostly to climatic change

ABSTRACT. At Ounjougou, a site complex situated in the Yamé River valley on the Bandiagara Plateau (Dogon country, Mali), multidisciplinary research has revealed a rich archaeological and paleoenvironmental sequence used to reconstruct the history of human-environment interactions, especially during the Late Holocene (3500-300 cal BC). Geomorphological, archaeological, and archaeobotanical data coming from different sites and contexts were combined in order to elaborate a chronocultural and environmental model for this period. Bayesian analysis of 54 14 C dates included within the general Late Holocene stratigraphy of Ounjougou provides better accuracy for limits of the main chronological units, as well as for some particularly important events, like the onset of agriculture in the region. The scenario that can be proposed in the current state of research shows an increasing role of anthropogenic fires from the 3rd millennium cal BC onwards, and the appearance of food production during the 2nd millennium cal BC, coupled with a distinctive cultural break. The Late Holocene sequence ends around 300 cal BC with an important sedimentary hiatus that lasts until the end of the 4th century cal AD.

International audienc

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Many societal and environmental changes occurred between the 2nd millennium BC and the middle of the 2nd millennium AD in western Africa. Key amongst these were changes in land use due to the spread and development of agricultural strategies, which may have had widespread consequences for the climate, hydrology, biodiversity, and ecosystem services of the region. Quantification of these land-use influences and potential feedbacks between human and natural systems is controversial, however, in part because the archaeological and historical record is highly fragmented in time and space. To improve our understanding of how humans contributed to the development of African landscapes, we developed an atlas of landuse practices in western Africa for nine time-windows over the period 1800 BC-AD 1500. The maps are based on a broad synthesis of archaeological, archaeobotanical, archaeozoological, historical, linguistic, genetic, and ethnographic data, and present land use in 12 basic categories. The main differences between categories is the relative reliance on, and variety of, domesticated plant and animal species utilized, and the energy invested in cultivating or keeping them. The maps highlight the irregular and frequently non-linear trajectory of land-use change in the prehistory of western Africa. Representing an original attempt to produce rigorous spatial synthesis from diverse sources, the atlas will be useful for a range of studies of human-environment interactions in the past, and highlight major spatial and temporal gaps in data that may guide future field studies.