The Seasonal Mobility Model for Prehistoric Herders in the South-western Cape of South Africa Assessed by Isotopic Analysis of Sheep Tooth Enamel

Abstract

A pattern of seasonal mobility between the coast and the hinterland by Khoekhoe pastoralists in the south-western Cape of South Africa was documented at the time of European contact. Because the region is characterized by a mosaic of geological substrates of various ages and vegetation types with different proportions of C3 and C4 plants, this mobility model for prehistoric herders can be tested by analysis of carbon, oxygen and strontium isotope ratios in domestic bovid tooth enamel. Isotopic analysis was performed on archaeological sheep, cattle, eland and steenbok teeth from the Late Stone Age site of Kasteelberg on the Vredenburg Peninsula. Sequential sampling of enamel provided a chronological record of the isotopic composition of diet during tooth formation. Results from carbon and oxygen isotope analysis of archaeological and modern steenbok teeth show seasonal variation in the δ13C of local pastures in the vicinity of the site (up to 2·9‰ in a single individual), which could be due to seasonal change in proportions of C3 and C4 plants and/or seasonal variation in the δ13C of C3 plants. A pattern of seasonal change of 0·9–3·5‰ in the δ13C of tooth enamel is also observed in the sheep teeth. This amplitude of variation could be due to local seasonal changes, thus it is not possible, from the δ13C values, to infer whether the sheep were moving seasonally. Results from 87Sr/86Sr analysis of two sheep suggest that one individual stayed all year round on the coast, whereas the other had grazed in the interior for part of its life. Both δ13C and 87Sr/86Sr values measured in a cow tooth suggest that this animal spent part of its life in the interior, even though it died at Kasteelberg. Results on this cow also suggest longer residence within habitats rather than seasonal mobility. A clear pattern of seasonal mobility between the coast and the interior has not been shown for prehistoric pastoralists. However, the pattern of mobility attested in historical times might have developed only later in prehistory, when cattle pastoralism developed in the region.