Climate change 'spurred modern human behaviour'

Sites in southern Africa preserve a rich record of early human culture

Abrupt climate change in Africa helped trigger technological and cultural advances in early modern humans, according to new research.

Archaeologists had long noted that the complexity displayed by human groups moved in fits and starts.

But there has been a debate about the causes of this stop-start pattern.

Analysis of marine sediments suggest a close link between changes in human behaviour and changes in the southern African climate.

The research by a British, Swiss and Spanish team is published in the journal Nature Communications.

The marine sediment core drilled off the coast of South Africa provides a record of climate variability over the last 100,000 years.

Co-author Martin Ziegler, from Cardiff University, said: "We found that South Africa experienced rapid climate transitions toward wetter conditions at times when the Northern Hemisphere experienced extremely cold conditions."

These large Northern Hemisphere cooling events have previously been linked to a change in the Atlantic Ocean circulation that led to the reduced transport of warm water to high latitudes.

The southern African climate responded in the opposite direction, with increasing rainfall associated with a southward shift of the tropical monsoon belt.

Prof Ian Hall, also from Cardiff, explained: "When the timing of these rapidly occurring wet pulses was compared with the archaeological datasets, we found remarkable coincidences.

"The occurrence of several major Middle Stone Age [tool] industries fell tightly together with the onset of periods with increased rainfall."

"Similarly, the disappearance of the industries appears to coincide with the transition to drier climatic conditions."

The archaeological record in southern Africa is vital for understanding the development of modern behaviour in humans, because it contains some of the oldest evidence for symbolism and personal adornments.

"Climate-driven pulses in southern Africa and more widely were probably fundamental to the origin of key elements of modern human behaviour in Africa, and to the subsequent dispersal of Homo sapiens from its ancestral homeland," the scientists wrote in Nature Communications.

Prof Chris Stringer, from London's Natural History Museum, who was also an author on the paper, said: "The quality of the southern African data allowed us to make these correlations between climate and behavioural change.

"But it will require comparable data from other areas before we can say whether this region was uniquely important in the development of modern human culture."