THE Highway area is home to an important Stone Age archaeological site called Umhlatuzana Rock Shelter.
The shelter, situated in the Giba Gorge Nature Reserve, is not open to the public due to its inaccessible location and important historical value. Umhlatuzana Rock Shelter houses deposits from the past 100 000 years, a period that includes parts of the Middle (300 000 to 25 000 years ago) and Later Stone Ages (25 000 years ago to Colonial times). There are several archaeological sites in South Africa of a similar age.
International archaeologists regularly visit, excavate and study South African Stone Age sites. The most recent excavation at the Umhlatuzana Shelter was undertaken by a team led by Dr Gerrit Dusseldorp from Leiden University in the Netherlands.
One reason for the interest in Stone Age sites such as Umhlatuzana is that genetic work in preceding decades showed that cognitively modern humans emerged in Africa.
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Dr Gavin Whitelaw, an archaeologist at the Natal Museum, says, “The fossil evidence shows an initial movement of archaic Africans out of Africa about two million years ago. Genetic evidence then revealed a second movement of humans out of Africa between 70 000 to 90 000 years ago. This second movement consisted of cognitively modern humans who spread across Eurasia, Australasia and the Americas.”
Whitelaw maintains that it was this genetic work that sparked an increased interest in South African Middle Stone Age sites by national and international researchers.
According to Whitelaw, there was less interest in the Middle Stone Age when the archaeological site was discovered in 1983 at the time when the nearby N3 freeway was under construction. Jonathan Kaplan, a Master’s student at the University of Cape Town, first excavated at Umhlatuzana due to concerns that the road construction might destroy the site.
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Whitelaw says, “Once we realised that it was in Africa that cognitively modern humans emerged, suddenly, these South African sites became of greater interest, and that’s why we’ve seen the flourishing of Middle Stone Age research in South Africa over the past 25 years, which is yielding wonderful results.”
Scientists focused on this phase in our collective history are fondly called deep-time archaeologists, and they study a period in which much organic material has often disappeared, leaving only layers of soil, some charcoal, stone implements and rarely, tiny fragments of bone. Archaeologists must use advanced technology to gather their data because of the limited remaining evidence. One such technology is Optically Stimulated Luminescence (OSL) Dating.
OSL Dating is a process of measuring the length of time a single grain of sand has been shielded from sunlight, thereby effectively and accurately measuring the last time the soil at the bottom of the excavation was on the surface of a site.
Dusseldorp’s team collected grains of sand in the dark at Umhatuzana Shelter. The grains would then be exposed to light and the released energy measured. After careful comparisons between measurements of background radiation of sand still in the site deposit and the sample grains, the difference between the two measurements provides the length of time since the sand in the excavation was buried and last exposed to daylight.
