Today’s arid Kalahari was once home to modern Homo sapiens who sheltered among waterfalls, stored water in ostrich eggshell containers and collected beautiful crystals.
This picture of thriving human life is painted by new research from a team of international scientists including University of Cape Town (UCT) geologist Dr Robyn Pickering, PhD candidate Jessica von der Meden, Master’s student Wendy Khumalo, and UCT Honours alumni Amy Hatton.
Published in the journal Nature on 31 March 2021, the work reveals evidence of complex human behaviours at Ga-Mohana Hill in the Northern Cape, South Africa dating back to 105,000 years ago – the same age when those behaviours occurred on the coast.
Identifying ostrich eggshell fragments, calcite crystal caches and ancient tufa deposits from this period of the Middle Stone Age, the researchers not only challenge long-held theories of human evolution but show our early ancestors lived in a water-rich Kalahari.
Ostrich Eggshell (OES) found at Ga-Mohana Hill (L). Example of OES water container (R).
“This is a story of water in what we know now as a dry landscape, and of human ancestors who exploited the landscape to not only survive but to thrive,” says Pickering, who is director of the Human Evolution Research Institute (HERI) at UCT.
Ga-Mohana Hill is in the southern Kalahari Basin, over 600km from the nearest coastline. The name Kalahari is derived from the Tswana word Kgala, meaning ‘great thirst’.
However, ancient proof of abundant water on the landscape is evident from striking tufa formations. The tufas were aged using the uranium-thorium dating method by von der Meden to between 110,000 and 100,000 years ago – exactly the same time period as the early modern humans were living there.
“We’re showing a record of water in the rocks that not only matches the archaeological record but also provides evidence of a crucial resource for the people living at Ga-Mohana,” says von der Meden.
Tufa formations at Ga-Mohana Hill which show past water on the Kalahari.
Hatton’s work on the project supports this. Working with the archaeological assemblages, she and the team identified ostrich eggshell fragments that may have been used as containers for water.
Armed with this paleoenvironmental record, and past research indicating an ancient mega-lake in the region, the work also provides clues about drivers of climate change in the region.
“Ga-Mohana Hill is dry for a reason, but there’s not much research into the hydrology of the Northern Cape, so we don’t know exactly why,” says Khumalo.
“But it’s not a simple answer,” Khumalo says. “In fact, it seems that multiple systems such as El Niño, changing sea surface temperatures and complex Indian Ocean dynamics work together to produce past rainfall in the region.”
As young researchers, Khumalo, Hatton and von der Meden had notable autonomy on the project, making observations, taking samples and putting sense to the findings largely on their own. “Their work contributes crucial pieces of the puzzle presented in this paper,” says Pickering.
HERI students Wendy Khumalo (L) and Jessica von der Meden (R) at Ga-Mohana Hill.
South Africa’s understudied interior may hold even more keys to the past than what’s revealed in this work, including insights into climate change and the origins of our species.
Indeed, South Africa’s human evolution research has largely been confined to coastal regions, at sites like Blombos Cave and Pinnacle Point, where evidence shows that our ancestors adapted to using marine resources, like eating shellfish, for example. Based on this evidence, some suggest the origins of our species was closely linked to the coast.
“Our findings mean we need to avoid overly simple models for the origins of our species. And it’s important to invite collaboration with diverse and young scientists to examine the many, largely understudied regions that were involved in shaping who we are today,” says study lead author Dr Jayne Wilkins, from Griffith University in Australia.