Views from Rhino Cave, Tsodilo Hills, Botswana

Sheila Coulson, Sigrid Staurset and Nick Walker Coulson:2011 (doi isn't working yet, so here's a PDF link, 12 MB) have published a long summary of findings from Rhino Cave, in the Tsodilo Hills of northern Botswana. These hills are huge isolated rock formations, or inselbergs, that jut out of relatively flat surrounding countryside. That makes them highly visible in the folklore and traditions of local people, and some caves in them have been used by people for tens of thousands of years.

Coulson and colleagues describe the setting of Rhino Cave, named for a rock painting within it.

It is...easy to understand how the site evaded detection, as it is perched high on the northernmost ridge of Female Hill and can only be approached by scrambling over, or squeezing between, massive boulders. Gaining entry to the cave is only slightly less arduous. On the western side of the ridge there is a raised, narrow, crawl space that ends with a considerable drop into the site. Alternatively, the wider eastern entrance offers two options: a two-meter jump or a slide down a steep boulder face, followed by a scramble over a rock-strewn opening near the present day floor.

I love these kinds of sites where you know that every lithic was brought in by people. That can tell you a lot about how people used the site, and the authors use that to advantage. But Coulson and colleagues do not yet have new dates for the deposits. The old dates appear too recent and are problematic because of their mismatch with other local MSA sites such as White Paintings Shelter and ≠Gi, both between 66,000 and 95,000 years old. The Rhino Cave assemblage may be comparable to these in age. The paper reports that substantial amounts of exotic stone materials including silcrete and chalcedony must come from more than 50 or 100 km away, respectively.

MSA exotic flakes from Rhino Cave, figure 5 from Coulson et al. 2011

Some of the flakes made from exotic raw materials, Figure 5 from the paper. All photos in the article copyrighted and used courtesy of Sheila Coulson.

There is a lot to the lithic collection besides the points, but I think these are interesting and certainly visually striking.

MSA points from Rhino Cave, figure 4 from Coulson et al. 2011

Coulson and colleagues noticed that many of the points were burned, and this was not easily explained by the incidental presence of fires in the cave, nor did it particularly appear to be explained in terms of the "heat-treating" that people used to make silcrete more suitable for artifact production at some other MSA sites.

In summary, there is a very distinctive pattern of burning at this site. A group of 26 MSA points and their associated debitage are heat damaged to the point of destruction. However, they have not been exposed to long-term burning of the type that is commonly found when an artifact is discarded into a hearth -- a common feature on any number of Stone Age sites. It is suggested that these MSA points and their associated manufacturing debitage were selectively and intentionally burnt in short-term restricted fires that caused their coloring to change to various reddish hues.

This is part of what Coulson and colleagues tentatively call evidence of symbolic or ritual behavior at the site. People climbed up to this out-of-the-way place with colorful stone from far away. The manufacturing debris shows that they made stone points in the cave. And they then left many of those points in the cave, some of them burned and destroyed or abandoned. At a minimum, it's curious. Adding everything together (including the cupules discussed below), it seems clear that the site was not used for purely utilitarian purposes. What that means about ancient social or cognitive systems is not obvious.

The article is open access, and full of amazing full-size color photos. I don't know why everyone doesn't publish their sites this way. For example, here's a photo of the site and night, where Coulson and colleagues experimented with flickering light against the carved wall:

Rhino Cave, night-time flicker light, figure 17 from Coulson et al. 2011

This stone face, which has been pecked at and scooped out for many thousands of years, is the most distinctive aspect of the site. Coulson and colleagues believe that some of the existing marks reflect very great antiquity, and they have natural spalls of the rock face that broke off in MSA times and integrated themselves into MSA layers. Some (maybe most) of the cupules are recent, and the pictorial art inside the cave is also late. But at least some of the surface carving appears to have been MSA in age.

Rhino Cave, cupules in rock wall, figure 12 from Coulson et al. 2001

Cupules in rock face, detail.

The paper discusses some evidence for pigment grinding at the site, including smooth-edged pieces of specularite and several small striated sandstone slabs (say that fast five times) presumably used as grindstones. Color goes together with the burning (to enhance color?), but this combination is not found elsewhere. Rhino Cave is in that way unique.

They indicate that the rock face is exposed to flickering daylight through a shaft at certain times, which they attempted to simulate with the flickering light photograph. Really I can't think of any better way to give readers an impression of what it would be like to visit the site.