Populations and Climatic Evolution in North Tropical Africa from the End of the Neolithic to the Dawn of the Modern Era

Abstract

At the end of the Neolithic Era, during the third millennium BCE, there were fewer humid periods, and the sub-Saharan and Sahelian zones from the Atlantic to Lake Chad assumed their current geographical form. Since then, the climate has continued undergoing major variations. The succession of climatic episodes, humid or dry, is pointed out along with the episodes' complex interactions. These variations are placed in parallel to cultural phases of evolution in archaeology and history. Climate-related events have always had heavy consequences on the peopling of this vast region, often subject to extreme natural conditions. The relative synchronism between the principal cultural trends from west to east across the Sahel seems to have often been subject to swings in the climate and the resulting environmental changes.Résumé La fin du Néolithique, au cours du III e millenaire BP, a correspondu à l'affaiblissement des périodes humides et à la mise en place de la géographie actuelle dans la zone sud-saharienne et sahélienne, qui s'etend de l'Atlantique au lac Tchad. Depuis cette époque le climat a cependant continué à beaucoup varier. La succession des differents épisodes climatiques, phases humides ou phases arides-et leurs interactions complexes-est precisée. Ces faits climatiques sont mis en parallèle avec l'évolution archéologique et historique des differentes phases culturelles. Dans cette immense region, souvent à la limite des conditions naturelles extrêmes, les évènements climatiques ont toujours eu des conséquences très importantes sur l'évolution des peuplements humains. Le relativement bon synchronisme des principaux changements culturels, d'ouest en est à travers la bande sahélienne, paraît avoir été fréquemment Afr Archaeol Rev (2015) 32:179-232 contrôlé par le rôle directeur des changements climatiques majeurs et des variations environnementales qui en ont resulté.

Subsistence strategy was the main factor driving population differentiation in the bidirectional corridor of the African Sahel

“…It was practiced by groups of cattle keepers who seasonally cultivated cereal crops while supplementing their food supply by hunting and gathering, as evident from many Neolithic sites (Clark & Gifford‐Gonzalez, ; Mercuri, Fornaciari, Gallinaro, Vanin, & di Lernia, ; Ozainne et al, ; Sereno et al, ). Nomadic pastoralism (with full dependence on animal husbandry) appeared only after the invention of iron metallurgy and was preceded by a wide range of mixed subsistence types which included combinations of hunting, gathering, animal husbandry, and crop cultivation (Linseele, ; Maley & Vernet, ). According to this theory, the split between the current nomadic pastoralists and sedentary farmers is relatively recent and the two populations share a common ancestry.…”

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“…Finally, the abandonment of agricultural sites along the Niger River in large portions of Mali, Burkina Faso, Niger, and northern Benin is shown on the map of AD 1500. While Maley and Vernet (2015) have reported that climatic instabilities led to unstable flow levels in the Middle Niger River from the eighth to fifteenth centuries, and large fluctuations in the Inland Niger Delta, they suggest that these had significant consequences for regional populations and political bodies in the thirteenth to sixteenth centuries. However, Huysecom, Ozainne et al (2015) do not believe that environmental factors can be blamed for the abandonment of Seno Plain sites in the fourteenth century, and changing socio-political and economic circumstances may have played a larger role in some areas (Albert et al 2000;Champion and Fuller 2018b).…”

“…The distribution of deep-water rice (common in the Inner Niger Delta) and décrue millets or sorghum would have varied annually and inter-annually with changes in regional climate and monsoon strength (Armitage, Bristow and Drake 2015;Maley and Vernet 2015), because these would have affected not only water levels but also the physical geography of the land forms on the floodplain, particularly in the Inland Niger Delta (Jacobberger 1987;R. J. McIntosh 1983).…”

A fluid past: Socio‐hydrological systems of the West African Sahel across the long durée

“…Fine sands in the water column of Lake Yoa in northeastern Chad indicate higher wind speed and/or dune formation across the region (Francus et al, ). The remobilization of dunes (Bristow & Armitage, ), and a “slight degree” of local block elevation, constricted the meandering of the Senegal River, driving its generally fixed and incised position (i.e., Maley & Vernet, ). To the east, the discharge of the Niger reduced significantly and the Interior Delta shrank by 50% of the size it had reached during the previous humid periods (Hassan, ).…”