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105,000-Year-Old Kalahari Crystals Challenge Cultural Evolution Story

105,000-Year-Old Kalahari Crystals Challenge Cultural Evolution Story

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New research at a rockshelter on the edge of the Kalahari Desert in South Africa challenges the assumption that modern human origins and complex behaviors were limited to coastal environments. A collection of unusual artifacts that are more than 100,000 years old 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 located in southern Africa. Since many of the archaeological sites linked to early human activity are located on the coast, experts assumed that Homo sapiens evolved their technological and symbolic behavior in that region as well. But a new study published in the journal Nature paints a very different picture.

One of the stone tools excavated from Ga-Mohana Hill North Rockshelter. (Credit: Jayne Wilkins)

One of the stone tools excavated from Ga-Mohana Hill North Rockshelter. (Credit: Jayne Wilkins)

The Oldest Proof 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 (370 miles) inland. Study lead author, Dr. Jayne Wilkins of Griffith University's Australian Research Centre for Human Evolution, explained the significance of the discovery in a University of Innsbruck press release, saying:

“Our findings from this rockshelter show that overly simplified models for the origins of our species are no longer acceptable. Evidence suggests many regions across the African continent were involved, the Kalahari being just one […] There have been very few well-preserved, datable archaeological sites in the interior of southern Africa that can tell us about Homo sapiens' origins away from the coast. A rockshelter on Ga-Mohana Hill that stands above an expansive savannah in the Kalahari is one such site.”

According to the press release, the scientists’ work has also provided “the oldest proof for modern humans in the Kalahari Desert in Africa.”

Archaeological excavations at Ga-Mohana Hill North Rockshelter where early evidence for complex Homo sapiens behaviors was recovered. (Credit: Jayne Wilkins)

Archaeological excavations at Ga-Mohana Hill North Rockshelter where early evidence for complex Homo sapiens behaviors was recovered. (Credit: Jayne Wilkins)

Looking at “Miniature Clocks”

An analysis of the site and the artifacts found at the rock shelter provides evidence that the behavior patterns of Homo sapiens at the site paralleled what was happening at the coast 100,000 years ago. The primary evidence comes from a collection of calcite crystals and fragments of ostrich eggshell, which the researchers believe may have been used as a container for water storage.

By using Optically Stimulated Luminescence (OSL), the team determined the age of the different 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 headed the OSL analysis, explained the technique:

“This method exploits natural light signals that accumulate through time in sedimentary quartz and feldspar grains. You have to think about each grain as a miniaturized clock. Under controlled laboratory conditions we can read out this natural light or 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 Kalahari Desert’s climate used to be much wetter – as evident from the tufa (a type of limestone) formations found around the rock shelter. Uranium-thorium dating of these features provide an age of between 110,000 and 100,000 years – the same time as the ancient humans were inhabiting the site.

A Collection of Kalahari Crystals – Symbols of a Very Ancient Sacred Palace?

At first the collection of 22 calcite crystals presented something of a mystery because, unlike the ostrich shell pieces, the researchers couldn’t see any obvious utilitarian purpose for them. Then they decided that was a clue. Dr. Wilkins said, “Our analysis indicates that the crystals were not introduced into the deposits via natural processes, but were deliberately collected objects likely linked to spiritual beliefs and ritual.”

Crystals collected by early Homo sapiens in the southern Kalahari 105,000 years ago. (Credit: Jayne Wilkins)

Crystals collected by early Homo sapiens in the southern Kalahari 105,000 years ago. (Credit: Jayne Wilkins)

Study co-author Dr. Sechaba Maape from the University of the Witwatersrand agrees and said that “This is remarkable considering that site continues to be used to practice ritual activities today.” The archaeological team is conscious of the fact that Ga-Mohana Hill still holds spiritual significance for local communities, and they say that they try to limit their impact on the local use of the rock shelter site. “Leaving no visible trace and working with the local community is critical for the sustainability of the project,” Dr. Wilkins noted, that this is also important “So that Ga-Mohana Hill can continue to provide new insights about the origins and evolution of Homo sapiens in the Kalahari.”

The archaeological site at a rock shelter in South Africa's Kalahari Desert. More than 100,000 years ago, people used the so-called Ga-Mohana Hill North Rockshelter for spiritual activities. (Credit: Jayne Wilkins)

The archaeological site at a rock shelter in South Africa's Kalahari Desert. More than 100,000 years ago, people used the so-called Ga-Mohana Hill North Rockshelter for spiritual activities. (Credit: Jayne Wilkins)

The article, titled “Innovative Homo sapiens behaviours 105,000 years ago in a wetter Kalahari,” is published in the journal Nature.

Top Image: Calcite crystal being excavated from 105,000-year-old deposits at Ga-Mohana Hill North Rockshelter in South Africa's Kalahari Desert. Source: Jayne Wilkins

By Alicia McDermott

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Pretty interesting 

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