Palaeoproteomics gives new insight into early southern African pastoralism

Abstract

The advent of domestication is a major step that transformed the subsistence strategies of past human societies. In Africa, domestic caprines (sheep and goat) were introduced in the north-eastern part of the continent from the Near East more than 9000 years ago. However, their diffusion southwards was slow. They are thought to have made their first appearance in the southern part of the continent ca. 2000 years ago, at a few Later Stone Age sites, including Leopard Cave (Erongo region, Namibia), which provided the oldest directly dated remains assigned to sheep or goat on the basis of morphology of bones and teeth. However, similarities in morphology, not only between these two domesticated caprine species, but also between them and the small wild antelopes, raised questions about the morphological species attribution of these remains. Additionally, the high fragmentation of the site's osteological remains makes it difficult to achieve species-level taxonomic identification by comparative anatomy. In this paper, we report molecular species identification of the Leopard Cave remains using palaeoproteomics, a method that uses protein markers in bone and tooth collagen to achieve taxonomic identification of archaeological remains. We also report new direct radiocarbon dates. Wild antelope remains from museum collections were used to enrich the available protein record and propose de novo type I collagen sequences. Our results demonstrate that the remains morphologically described as domesticates actually belong to a wild antelope species and that domestic caprines first appeared at Leopard Cave 1500 years later than previously thought. This study illustrates that the use of palaeoproteomics coupled with direct radiocarbon dates is particularly suited to complement classic zooarchaeological studies, in this case concerning the arrival of the first herding practices in arid environments.

Figure 1

Map of southern Africa synthesizing all Later Stone Age sites from which caprine remains have been identified, including Leopard Cave (red dot), sites with remains attributed morphologically to caprines (after ref.) (green dots), and sites with directly radiocarbon dated remains attributed morphologically to caprines (after ref.) (orange dot). Site names circled in red refer to the three archaeological sites where caprine remains were molecularly identified (ref. and this study for Toteng and Leopard Cave; ref. for Blydefontein). Associated dates are given to the right of the map. The map was generated by Louise Le Meillour and David Pleurdeau using Google Maps (https://www.google.fr/maps) for country and river edges and created using Adobe Illustrator CC 2017 (https://www.adobe.com/).

Figure 2

Stratigraphy of squares N6/N7 and O6/O7 in Leopard Cave. The stratigraphic position of the remains included in the study is indicated by red circles. All radiocarbon dates obtained within the sequence are presented by depth. The two dates corresponding to the direct dating of the teeth morphologically identified as caprine are shown in blue.

Figure 3

Leopard Cave mid-sized bovid remains direct radiocarbon dates. Direct dates previously reported for what are now known, based on proteomics, to be two springbok remains are shown in blue (LC_113, LC_149). New radiocarbon dates on remains identified as sheep by palaeoproteomics are shown in grey (LC_131, LC_135). Radiocarbon dates were calibrated at 2 σ (95.4%) using OxCal 4.3 and the SHCal13 calibration curve, for the southern hemisphere.