Throughout Africa in at least 22 countries and even further afield are rocks with clusters of enigmatic pecked or drilled hemispherical hollows and/or rocks with ground-out grooves. It is probable that these carvings are much more common than realised, but they have often been ignored because of their ambiguity, lack of iconicity or because it is often thought that they are natural or mundane manufacturing tools. For example, copies or photographs of petroglyphs of animals and other subject matter in southern Africa often include dimple-like depressions or groove-like dashes or scratches that have seldom been commented on by the researchers (e.g. Wilman 1933; Fock 1979; but see Ouzman 2001). These carvings recall the hollows that may form on hammerstones or anvilstones, on the one hand, and grooves on whetstones for sharpening tools such as arrowpoints and axe- or adze-heads, on the other; indeed, their simple form probably has contributed to many being classified as ‘utilitarian’. However, the wear, shape, lack of associated waste from manufacturing or processing, context and arrangement or placement suggest other - wise for many. It seems that several may have served as religious symbols or been the ‘non-utilitarian’ byproducts of ritual activity, or perhaps included magical concepts in their use. Their frequency and size and the amount of effort put into their production certainly allude to their importance. Their simplicity and lack of iconicity, and the absence of any discernible meaningful patterning or syntax in their creation, suggest that they are not obviously examples of art as we understand it, especially when compared with rock paintings where the use of pigment clearly indicates an element of intentional symbolic design. Yet many appear to have served similar symbolic functions and so they are collectively regarded here as a form of rock art for convenience.

This chapter looks at these issues in an introductory examination of the carvings at Tsodilo Hills in northwest Botswana, where they are particularly common.