The Kalahari Desert, in southern Africa, is not normally considered a hotbed of Stone Age innovations. And yet, human culture flourished there about 105,000 years ago, when it was green, researchers say.
Calcite crystals and other finds in a South African rock shelter more than 600 kilometers from the nearest coastline reflect cultural behaviors on par with those previously reported of ancient humans living on or near the coast of South Africa, according to researchers on March 31 in Nature. These coastal deposits date back to about 125,000 and 70,000 years ago, including one where locals used tools to paint with pigments about 100,000 years ago (SN: 10/13/11).
Given the scarcity of human sites in that time period, it is difficult to know whether cultural innovations emerged independently in groups scattered across southern Africa or originated in a particular region before being adopted elsewhere. But the new findings fit into a scenario in which “the emergence of Homo sapiens involved the interaction of many different populations in Africa,” says archaeologist Jayne Wilkins of Nathan Griffith University in Australia. "And that included the Kalahari Desert."
Excavations at Ga-Mohana Hill North Rockshelter, or GHN, have uncovered an ancient layer of sediment containing 42 fragments of burnt ostrich eggshells and 22 palm-sized or smaller calcite crystals, Wilkins and colleagues report.
Like some groups of African hunter-gatherers today, ancient people of GHN may have cut holes in ostrich eggshells to create containers of water, the researchers say. Geological studies have indicated that once enough rain fell on the Kalahari Desert to produce year-round water sources for the ancient GHN people.
Many pieces of eggshell showed a discoloration from burning. It is unclear how that burning occurred. Eggshells lay among numerous animal bones, some of which showed possible butcher marks and signs of burning.
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Calcite crystals were probably collected from local rock sources, one of them about 2.5 miles from the rock shelter, scientists suspect. The excavated calcite crystals were not modified in any way and had no apparent practical use, which raises the possibility that these elements had a ritual or symbolic meaning, Wilkins suspects.
Crystals have been linked to spiritual beliefs and rituals in many parts of the world. So far, the oldest set of crystals dated about 80,000 years ago to another South African rock refuge located about 130 kilometers off the coast, Wilkins says.
Other GHN finds included hundreds of stone tools, prepared pieces of rock from which tools were struck, and a piece of red pigment with scraping marks.
Ancient cultural evolution in many parts of Africa remains a mystery, writes archaeologist Pamela Willoughby of the University of Alberta in Edmonton, Canada, in a commentary published with the new study. The calcite crystals found in GHN may represent "a first example of ritual symbolic behavior," according to Willoughby.
It is difficult to demonstrate any ritual use of GHN crystals, argues archaeologist Manuel Will of the University of Tübingen in Germany. Ostrich eggshell pieces found at Kalahari site could be discarded after a meal, he said.
Still, the new study adds to growing skepticism about claims that human cultural advances have begun along African coasts, says Will (SN: 29/07/11). However, it is possible that abundant habitats along the southern coast of Africa have fostered a particularly wide range of cultural innovations, he suggests. Coastal deposits produced items not found inside GHN, including beads, bone tools, and ostrich eggshells with engraved designs.