Bernie Goldie

New study pinpoints timing of archaeological innovations by early modern humans

Researchers from the University of Wollongong have shed new light on some of the longest-standing questions in African archaeology -- the timing of finely-crafted stone tools in southern Africa during the Middle Stone Age.

Dr Zenobia Jacobs and Professor Richard ‘Bert’ Roberts from the University of Wollongong (UOW) are lead authors of an international study published today (31 October) in the respected journal Science that offers new insights on two bursts of innovative technology and behaviour in the Middle Stone Age of southern Africa.

The distinctive archaeological artefacts include personal ornaments, symbolic items, and stone tools made into weapons by members of our species (Homo sapiens).

An international team of scientists, led by Dr Jacobs from UOW’s GeoQuEST Research Centre and the School of Earth and Environmental Sciences, tackled the intriguing questions -- when did the finely-crafted stone tools, known as the Still Bay and Howieson’s Poort industries, first appear in southern Africa, what catalysed their appearance, and what caused their sudden disappearance?

Dr Jacobs said that both of these industries occurred in the Middle Stone Age, which witnessed the emergence of Homo sapiens about 200,000 years ago, the evolution of fully ‘modern’ human behaviour, and the exodus of people out of Africa perhaps 60,000 years ago.

“This was a critical period in modern human evolution but the timing of the key turning points has been difficult to nail down,” she said.

The study, funded by the Australian Research Council, yields new evidence on these turning points, obtained by applying a systematic dating approach to nine archaeological sites spread across all major climatic and ecological zones in southern Africa – including the deserts of Namibia, the coasts of South Africa, and the mountains of Lesotho.

Archaeologists from South Africa, Germany, the UK and Australia helped collect sediment samples for state-of-the-art optically stimulated luminescence dating by Dr Jacobs, who analysed more than 50,000 individual grains of sand. With the expertise of statistician Dr Rex Galbraith (University College London), the team was able to pinpoint the timing of the start and end of the Still Bay and Howieson’s Poort industries.

“A key finding of our study is that both industries were short-lived and flourished in two separate but closely spaced bursts between 80,000 and 60,000 years ago – intriguingly, about the same time as human populations rapidly expanded in Africa, and people had begun to disperse across southern Asia to Australia,” Professor Roberts said.

The Still Bay industry is remarkable for the finely shaped stone tools that were probably parts of spearheads, and that appeared and disappeared within 1,000 years – a geological instant – after 100,000 years of comparatively unsophisticated artefacts. A further 7,000 years of time elapsed before the southern Africans began to make Howieson’s Poort tools, which most likely were hafted to make composite weapons.

“But this burst of innovation ended about 60,000 years ago, returning to a further 30,000 years of relatively crude stone-age technology,” Dr Jacobs said.

The reasons for the waxing and waning of these industries remain elusive. But Dr Jacobs and colleagues rule out environmental factors as being the main driving force for the emergence of these two periods of innovation.

“We see no consistent pattern between the timing of these industries and major climatic changes although local conditions probably influenced where people preferred to live,” Dr Jacobs said.

“It is also possible that the Still Bay and Howieson’s Poort innovations were the catalyst for the population expansions within and out of Africa – or that demographic events were the trigger for the advanced stone-age technologies.

“What we need now to answer these lingering questions are much tighter timeframes for human expansions and migrations, climatic changes, and other innovative archaeological industries in Africa,”, Dr Jacobs said.