Climate change did not encourage cultural and technological innovation among Mesolithic people, challenging the popular theory that this instability helped shape human society almost 100,000 years ago. Instead, researchers say periods when the climate was stable allowed people to experiment with different ideas, leading to the rise of things like bone tools and ornamentation.
The Middle Stone Age (Mesolithic period) in southern Africa was marked by huge cultural changes, with two sites in particular - Still Bay and Howiesons Poort – representing periods of innovation among early Homo sapiens. Still Bay was occupied between 98,000 and 73,000 years ago, while Howiesons Poort dates to between 72,000 and 59,000 years.
While this period is known to have had an unstable climate, disconnect between ancient environmental records and archaeological sites means it is not clear at which times technological advances were made. Previously, it was thought instability would have forced humans to come up with new and better means of surviving.
An international team of researchers analysed environmental records these sites work out the timings of technological breakthroughs and looked to see if they coincided with periods of climatic instability or stability. The team, led by Patrick Roberts from the University of Oxford, looked at the stable carbon and oxygen isotopes in ostrich eggshells, faunal remains and shellfish to work out the environmental conditions.
Their findings, published in PLOS One, showed climate change did not correspond with phases when Stone Age people were making technological advances at either sites. This indicates an unstable climate was not the driving force behind innovation among early humans.
"The results from both sites ... show significant changes in vegetation, aridity, rainfall seasonality, and sea temperature in the vicinity of the sites during periods of human occupation," they wrote. "While these changes clearly influenced human subsistence strategies, we find that the remarkable cultural and technological innovations seen in the sites cannot be linked directly to climate shifts."
They concluded: "Although our species has shown itself to be highly resilient in the face of climatic and environmental instability it is clearly not wholly dependent on such changes for its innovation."
Roberts added: "Our results suggest that although climate and environmental changes occurred, they were not coincident with cultural innovations, including personal ornamentation, or the appearance of complex tool-types. This suggests that we have to consider that other factors drove human innovation at this stage in our species' evolution."
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