Two years ago, I wrote about the archaeological assemblages and evidence of symbolic behavior at Rhino Cave, Botswana ("Views from Rhino Cave, Tsodilo Hills, Botswana". Another site in the same region is White Paintings Shelter, with MSA assemblages dating from 50,000 back to more than 90,000 years ago. A new paper by David Nash and colleagues has sourced the raw materials used in stone manufacture across this time range at the site  They show that long-distance transport of silcrete stone was a major component of the material record at the site. From the paper:
The people who used WPS were clearly aware of the available resources at Tsodilo Hills, anticipated a need, and procured silcrete from at least 220 km away for tool manufacture. The transport of raw materials from such distant sites represents a repeated procurement strategy for resource acquisition and suggests that these people made two conscious decisions. First, despite having ready access to local quartz and quartzite at Tsodilo Hills they chose to acquire silcrete. Second, they opted to use silcrete from south of the Okavango Delta (or possibly further afield during wetter periods) rather than from sources much closer to WPS. This is even though the hand specimen characteristics of silcrete samples from the Boteti River, Lake Ngami, Okavango River and Xaudum indicate that materials from these localities are equally fine-grained and well-cemented, and therefore likely to be of equivalent quality for tool manufacturing purposes.
The authors include a mini-review of other MSA sites with evidence of long-distance transport.
This is not the first study from the African MSA to identify the long-distance transport of stone raw materials by tool-manufacturing populations. In East Africa, for example, small numbers of obsidian artifacts from the Songhor and Muguruk MSA sites in western Kenya have been provenanced to volcanic flows up to 190 km distant (McBrearty, 1981, 1988). Obsidian artifacts from the Nasera Rock Shelter in northern Tanzania were procured from some of the same central Kenyan Rift sources, involving transport of up to 320 km (Merrick and Brown, 1984; Mehlman, 1989). The movement of raw materials over such distances has been interpreted to represent deliberate stone-collecting forays (see Merrick et al., 1994). What is, however, significant about our results is that, unlike the majority of sites where obsidian provenancing studies have been undertaken, silcretes are a major component of the MSA record at WPS. Indeed, obsidian artifacts make up typically only 1–5% of East African MSA assemblages (see McBrearty and Brooks, 2000; Ambrose, 2012; for reviews). The repeated long-distance transport of silcrete to WPS must therefore have represented a habitual resource procurement strategy for the MSA peoples who occupied the shelter.
Rare or occasional transport are not logistically difficult to explain. Neandertals transported raw materials in small quantities across more than 150 km. But this case is interesting because of the intensity of transport evidenced at White Paintings Shelter, in addition to the thousands of years across which the transport strategy was repeated.
- . Provenancing of silcrete raw materials indicates long-distance transport to Tsodilo Hills, Botswana, during the Middle Stone Age. Journal of Human Evolution. 2013 .