Ellipsoid grinding hollows on the west coast of South Africa

Abstract

Grinding hollows are found on rocks throughout much of Africa. Several sub-types exist, and Nick Walker has recently proposed the term 'ellipsoids' to describe those polished grooves, which are U-shaped in crosssection and have a canoe-shaped longitudinal profile. They are the result of a to-and-fro grinding action. Found on horizontal surfaces, ellipsoids are considered utilitarian objects, and many possible grinding functions have been attributed to them. Over a hundred such ellipsoids are recorded on the hill Kasteelberg, west coast of South Africa. Morphologically, the Kasteelberg examples resemble ellipsoids found as far north as the Tsodilo Hills in north-western Botswana. Although their specific function remains enigmatic, we argue that the Kasteelberg examples represent intensification in commodity production. Various lines of evidence suggest that this intensification took place during the early second millennium AD. Similar cases of intensified production can be seen at many sites of this period in Botswana and northern Namibia, where they have been interpreted as a response to the contemporary economic boom in the Shashe-Limpopo basin. Might the massed grinding hollows of Kasteelberg represent a similar economic reaction?