New research at a rock shelter on the edge of South Africa’s Kalahari Desert challenges the assumption that modern human origins and complex behaviors were limited to coastal environments. A collection of unusual artifacts dating back more than 100,000 years suggests that inland homo sapiens were just as innovative as their coastal cousins.
There is a widespread belief that the origins of modern humans and modern human cognition can be found in southern Africa. Since many of the archaeological sites related to early human activity are located on the coast, experts assumed homo sapiens developed their technological and symbolic behavior in that region as well. But a new study published in the journal Nature paints a completely different picture.
One of the stone tools excavated at Ga-Mohana Hill North Rockshelter. (Credit: Jayne Wilkins)
The oldest evidence for modern humans in the Kalahari Desert
An international team of scientists explored the Ga-Mohana Hill North Rockshelter, a site overlooking the savannah of the Kalahari Desert and more than 600 km inland. Lead author of the study, Dr. Jayne Wilkins of Griffith University’s Australian Research Center for Human Evolution, explained the significance of the discovery in a press release from the University of Innsbruck, saying:
“Our findings from this rock shelter show that overly simplified models of the origins of our species are no longer acceptable. Evidence suggests that many regions of the African continent were involved, of which the Kalahari is just one […] Few well-preserved archaeological sites in the interior of southern Africa can tell us about the origins of Homo sapiens off the coast. A rockshelter on the Ga-Mohana hill which stands above a vast savanna in the Kalahari is one such site. ”
According to the press release, the scientists’ work has also provided “the oldest evidence of modern humans in the Kalahari Desert in Africa.”
Archaeological excavations at Ga-Mohana Hill North Rockshelter were early clues to the complex homo sapiens behavior was restored. (Credit: Jayne Wilkins)
Watching “Miniature Clocks”
An analysis of the site and the artifacts found near the rock shelter provides evidence that the behavioral patterns of homo sapiens on the spot parallels what happened on the coast 100,000 years ago. The primary evidence comes from a collection of calcite crystals and ostrich eggshell fragments, which the researchers believe may have been used as a container for water storage.
Using Optically Stimulated Luminescence (OSL), the team determined the age of the various archaeological layers in which the artifacts were found and dated the objects to 105,000 years old. Michael Meyer, the head of the OSL laboratory at the Institute of Geology at the University of Innsbruck and the geologist who led the OSL analysis, explained the technique:
“This method uses natural light signals that accumulate over time in sedimentary quartz and feldspar grains. Think of each grain as a miniature clock. Under controlled laboratory conditions we can read this natural light or the so-called luminescence signal, which in turn informs us about the age of the archaeological sediment layers. The more light, the older the sediment. ”
The researchers also noted that the climate in the Kalahari Desert used to be much wetter, as evidenced by the tuff formations (a type of limestone) found around the rock shelter. Uranium-thorium dating of these features gives it an age of between 110,000 and 100,000 years – the same time as the ancient people inhabited the site.
A collection of Kalahari crystals – symbols of a very old sacred palace?
Initially, the collection of 22 calcite crystals was somewhat mysterious because, unlike the pieces of the ostrich shell, the researchers could see no clear utilitarian purpose for it. Then they decided that was a clue. Dr. Wilkins said, “Our analysis indicates that the crystals were not introduced into the deposits through natural processes, but were intentionally collected objects likely related to spiritual beliefs and ritual.”
Crystals collected early homo sapiens in the southern Kalahari 105,000 years ago. (Credit: Jayne Wilkins)
Study co-author Dr. Sechaba Maape of the University of the Witwatersrand agreed, saying, “This is remarkable given that the site is still used today for the practice of ritual activities.” The archaeological team is aware that Ga-Mohana Hill still has spiritual significance to local communities, and they say they are trying to limit their impact on the local uses of the rock shelter. “Leaving no visible trace and working with the local community is critical to the sustainability of the project,” noted Dr. Wilkins points out that this is also important. “So that Ga-Mohana Hill can continue to provide new insights into the origin and evolution of Homo sapiens in the Kalahari.”
The archaeological site at a rock shelter in the Kalahari Desert in South Africa. More than 100,000 years ago, people used the so-called Ga-Mohana Hill North Rockshelter for spiritual activities. (Credit: Jayne Wilkins)
The article entitled “Innovative homo sapiens behavior 105,000 years ago in a wetter Kalahari, ”the magazine said Nature
Top image: Calcite crystal is excavated from 105,000-year-old deposits on Ga-Mohana Hill North Rockshelter in South Africa’s Kalahari Desert. Source: Jayne Wilkins
By Alicia McDermott