Climate change and agropastoralist settlement in the Shashe-Limpopo River Basin, Southern Africa: AD 880 to 1700

The expansion and decline of complex socio-political farming systems in the Shashe-Limpopo River Basin, southern Africa, has been linked to large-scale climate shifts in which increased rainfall favoured intensified agropastoral production and expanded settlement, while the onset of and conditions led to collapse and abandonment of the area. This study uses stable nitrogen isotope ratios ((NN)-N-15-N-14) from modern and archaeological fauna to construct a proxy-rainfiall sequence for the region from AD 880 onwards. The resulting sequence provides a revised climatic context for agropastoral settlement of the river basin and evidence of greater climatic variation than previously documented. Stable nitrogen isotope data from the bone collagen of archaeological fauna show that settlement by Zhizo agropastoralists between AD 880 and 1010 took place under semi-arid conditions, with average annual rainfall of <500 mm. Results for sites dating between AD 1010 to 1290 are consistent with previous interpretations that the Leopard's Kopje A and B cultural period 'capitals' of K2 and Mapungubwe, respectively, rose to prominence under a trend towards increased average annual rainfall that was :500 mm. The data indicate also that the phase of increased moisture extended beyond the abandonment of Mapungubwe at AD 1290 and continued to be evident in fauna dating to the Moloko/Icon cultural period between AD 1310 and 1415. Data from the Moloko/Khami cultural period sites suggest that markedly drier conditions were not evident in the area until after AD 1450. Based on the isotope data, increased rainfall appears to have coincided with the expansion and intensification of settlement in the Shashe-Limpopo River Basin. Reconsideration, however, needs to be given to the correlation between the abandonment of Mapungubwe with the onset of and conditions unfavourable for agropastoralism; other explanations, encompassing socio-economic and political choices, also must be sought.