Pre-Colonial Herding Strategies in the Shashe-Limpopo Basin, Southern Africa, Based on Strontium Isotope Analysis of Domestic Fauna
Archaeological sites in the Shashe-Limpopo River Basin, southern Africa, reflect marked population growth and increased socio- political complexity between ca AD 880 and 1290, but the nature of agropastoral management that underpinned these extensive, more complex societies is not well understood. One key question concerns whether localized or more widespread regional strategies were employed to manage large herds of domestic animals. In order to identify potential herding areas we carried out strontium isotope analyses on tooth enamel from domestic fauna recovered at Shashe-Limpopo River Basin sites and compared them with those of modern wild and domestic fauna sampled from the greater region. Values were determined via low-resolution Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) and Laser-ablation ICP-MS and high-resolution, standard Thermal Ionization Mass Spectrometry (TIMS). The low-resolution approaches gave values comparable to data produced by TIMS, within the level of precision required to distinguish geological areas contained in this exceptionally isotopically variable environment. The less invasive laser-ablation ICP-MS method provided a means to sample tooth enamel increments for indications of inter-seasonal movement of livestock. The archaeological data suggest that an inter-seasonal geographical expansion of herd management took place as socio-political complexity increased. A trans-humance or relocating herding strategy would have limited overgrazing of the local river basin landscape and results allow us to revisit hypotheses that overgrazing and environmental deterioration contributed to the subsequent political collapse and abandonment of the river basin at ca AD 1290.