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Social factors shifted stone age technology

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A new study by scientists at the University of the Witwatersrand suggests that Stone Age humans began to settle down about 58 000 years ago, staying in one area for longer periods.
The research also provides a potential answer to a long-held mystery: why the older, Howiesons Poort complex technological tradition in South Africa, suddenly disappeared at that time.
The research paper by Dr Paloma de la Peña and Professor Lyn Wadley from the Evolutionary Studies Institute and the School of Geography, Archaeology and Environmental Studies at the University of the Witwatersrand in Johannesburg, South Africa, published in PlosOne, is titled: “Technological variability at Sibudu Cave: The end of Howiesons Poort and reduced mobility strategies after 62 000 years ago”.
De la Peña and Wadley explore the changes observed between an industry known as the Howiesons Poort (dated about 65 000 to 62 000 years ago at Sibudu) and the one that followed it at about 58 000 years ago.
Sibudu, a rock shelter near Tongaat in KwaZulu Natal, South Africa, has a long and diverse archaeological sequence.
The Howiesons Poort at Sibudu contains many finely-worked, crescent-shaped stone tools fashioned from long, thin blades made on dolerite, hornfels and, to a lesser extent, quartz. These “segments”, as they are called, were hafted to shafts or handles at a variety of angles using compound adhesives that sometimes included red ochre (an iron oxide).
A diverse bone tool kit in the Howiesons Poort includes what may be the world’s oldest bone arrowhead. Certainly a variety of hunting techniques was used perhaps including the first use of snares for the capture of small creatures. The animal remains brought to Sibudu reflect this diversity for there are bones from large plains game like zebra, tiny blue duiker, and even pigeons and small carnivores.
The beautiful Howiesons Poort industry with its long, thin blades was replaced 58 000 years ago by a simple technology that could be rapidly produced. Coarse rocks like quartzite and sandstone became popular. These could be collected close to Sibudu. Post-Howiesons Poort, tools were part of an unstandardised toolkit with triangular or irregularly-shaped flakes. Tiny scaled pieces were also produced using a bipolar technique (in the simplest terms this involves smashing a small piece of rock with a hammerstone).
There were many grindstones in Sibudu 58 000 years ago, and these were used to grind ochre and/or bone. The use of ochre also changed: silty ochre found close to Sibudu was popular 58 000 years ago and, rather than suggesting tasks different from earlier ones, people may have wanted to collect raw materials close to their camp.
Various types of evidence suggest that about 58 000 years ago people stayed in Sibudu longer than before. There was considerable, rapid accumulation of sediments built up in millimetre-thick lenses from stacked layers of burnt sedge and grass bedding — possibly because grass bedding became infested with pests so people could either burn bedding to clean the camp or move out.
Environmental factors do not seem to have caused the time-related technological and site-formation changes observed. The scientists are inclined to favour social transformation as the reason. It is possible that changes in band size and/or membership of the group influenced decisions about whether to stay in Sibudu.