New archaeological evidence from Africa’s interior challenges notions that the emergence of Homo sapiens relied on adaptations to coastal environments, according to an international team of scientists.
Excavations from a rock shelter at Ga-Mohana Hill on the edge of South Africa’s Kalahari Desert revealed signs of complex human behaviours 105,000 years ago, paralleling similar discoveries on the coast around the same time.
“The origin of our species was more complicated than we like to think,” says Jayne Wilkins from Griffith University, lead author of a paper published in the journal Nature.
One of the most important finds by her team was a collection of 22 calcite crystals.
“Crystals have had spiritual significance around the world for many time periods,” Wilkins explains. “I think the crystals at Ga-Mohana were probably collected for some of the same reasons that people collect crystals today and throughout prehistory – for their visually striking properties and beauty, and perhaps to play a role in ritual activities.
“So, people in the Kalahari were not ‘archaic’ or less complex than humans living at the coast at the same time.”
Wilkins had previously worked on coastal sites with her collaborators but remained curious about the archaeological record from Middle Stone Age sites further inland, of which very little is known.
After excavating the rock shelter, she led a team of researchers from eight institutions in five countries, including local South African collaborators and community members, to establish the significance of the finds, how old they were and what the palaeoenvironment was like.
They analysed its chronology using luminescence dating. “This technique measures natural light signals that accumulate over time in sedimentary quartz and feldspar grains,” says co-author Michael Myer from the University of Innsbruck in Austria.
“You can think about each grain as a miniaturised clock, from which we can read out this natural light or luminescence signal, giving us the age of the archaeological sediment layers.”
As well as the crystals, the team found fragments of ostrich eggshells, which may have been used as water containers. The eggshells were older than those reported in interior environments elsewhere.
While the Kalahari (named from the Tswana word Kgala meaning “great thirst”) is semi-arid today, tufa formations around the shelter indicate that there used to be flowing water. Uranium-thorium dating placed this wet period at the same time the people lived there.
“This is a story of water in what we know now as a dry landscape,” says Robyn Pickering from the University of Cape Town, “and of adaptable people who exploited the landscape to not only survive but to thrive.”
Africa’s archaeological record has provided our earliest insights into the emergence of Homo sapiens and the symbolic and technical advances that typify our species. With rare well-preserved sites inland, Wilkins and colleagues say this has led to a narrative dominated by remains from coastal settings. The new discovery throws this into question.
“Our results suggest that behavioural innovations among humans in the interior of southern Africa did not lag behind those of populations near the coast, and that these innovations may have developed within a wet savannah environment,” they write.
“Models that tie the emergence of [those] innovations to the exploitations of coastal resources by our species may therefore require revision.”
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