According to a study by the Universitat Autònoma de Barcelona(UAB) , the University of Cardiff and the Natural History Museum in London, technological innovation during the Stone Age occurred in fits and starts and was climate-driven. Abrupt changes in rainfall in South Africa 40,000 to 80,000 years ago triggered the development of new technologies for finding refuge and as a consequence – much of the behaviour of modern humans.
This study was recently published in Nature Communications.
A driver for change
The development of early human populations has often been linked to pulsed phases of technological and behavioural innovation within the Middle Stone Age of South Africa. However, the trigger for these intermittent pulses of technological innovation is an enigma.
The new study shows that contrary to previous work, the occurrence of innovation was tightly linked to abrupt climate change. Major pulses of activity evidenced by technological or behavioural change occurred during periods when South African climate changed rapidly towards more humid conditions, while northern sub-Saharan Africa experienced widespread droughts, as the Northern Hemisphere entered phases of extreme cooling.
These millennial-scale experiences resulted from the seesaw behaviour of the Atlantic Ocean related to changes in the ocean circulation. These conditions led to humid pulses in South Africa and potentially to the creation of favourable environmental conditions for change.
The evidence
Archaeological and genetic evidence suggests that modern humans (the present form of Homo sapiens, our species) originated in Africa during the Stone Age, between 30,000 and 280,000 years ago. The latest archaeological excavations in southern Africa have shown that technological innovation, linked to the emergence of culture and modern behaviour, took place abruptly: the beginnings of symbolic expression, the making of tools from stone and bone, jewellery and the first agricultural settlements.
Over the last million years the global climate has varied between glacial periods (with great masses of ice covering the continents in the northern hemisphere) and interglacial periods, with changes approximately every 100,000 years. But within these long periods there have been abrupt climate changes, sometimes happening in the space of just a few decades, with variations of up to 10ºC in the average temperature in the polar regions caused by changes in the Atlantic ocean circulation. These changes affected rainfall in southern Africa.
The researchers have pieced together how rainfall patterns varied in southern Africa over the last 100,000 years, by analysing river delta deposits at the edge of the continent, where every millimetre of sediment core corresponds to 25 years of sedimentation. The ratio of iron (dissolved from the rocks by the water during the rains) to potassium (present in arid soils) in each of the millimetre layers is a record of the sediment carried by rivers and therefore of the rainfall throughout the whole period.
The reconstruction of the rainfall over 100,000 years shows a series of spikes that occurred between 40,000 and 80,000 years ago. These spikes show rainfall levels rising sharply over just a few decades, and falling off again soon afterwards, in a matter of centuries. This research has shown that the climate changes coincided with increases in population, activity and production of technology on the part of our ancestors, as seen in the archaeological records. In turn, the end of certain stone tool industries of the period coincides with the onset of a new, drier climate.
The findings confirm one of the principal models of Palaeolithic cultural evolution, which correlates technological innovation with the adoption of new refuges and with a resulting increase in population and social networks.
Source: Universitat Autonoma de Barcelona
More Information
The study forms part of the GATEWAYS (www.gateways-itn.eu) project of the European Commission’s 7th Framework Programme
Martin Ziegler,Margit H. Simon,Ian R. Hall,Stephen Barker,Chris Stringer & + et al. Development of Middle Stone Age innovation linked to rapid climate change Nature Communications 4, 1905 doi:10.1038/ncomms2897
Cite this article
Universitat Autonoma de Barcelona. Climate drives human innovation during African Stone Age. Past Horizons. June 26, 2013, from Permalink: http://www.pasthorizonspr.com/index.php/archives/06/2013/climate-drives-human-innovation-during-african-stone-age
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