Scientists excavating a Stone Age cave on South Africa’s southern coast have followed a trail of engraved pigments to what they suspect are the ancient roots of modern human behavior.
Analyses of 13 chunks of decorated red ochre (an iron oxide pigment) from Blombos Cave indicate that a cultural tradition of creating meaningful geometric designs stretched from around 100,000 to 75,000 years ago in southern Africa, say anthropologist Christopher Henshilwood of the University of the Witwatersrand in Johannesburg and his colleagues. Their report appears online and in an upcoming Journal of Human Evolution.
Much debate surrounds the issue of when and where language, religion, symbolic decorations and other facets of modern human behavior originated. Researchers such as Henshilwood hypothesize that modern human behavior developed gradually in Africa, beginning more than 100,000 years ago. Others posit that a brain-boosting genetic mutation around 50,000 years ago fostered modern behavior in Africa. Some researchers suspect that behavioral advances first appeared in Europe, Asia and Africa at that later time.
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Possible examples of symbolic behavior from around 100,000 years ago — such as proposed human burials in the Middle East and pigment use in Africa — have been controversial.
“What makes the Blombos engravings different is that some of them appear to represent a deliberate will to produce a complex abstract design,” Henshilwood says. “We have not before seen well-dated and unambiguous traces of this kind of behavior at 100,000 years ago.”
Further studies need to confirm that the ancient incisions were not the result of, say, slicing into ochre with stone tools in order to remove powder quickly, cautions anthropologist Curtis Marean of Arizona State University in Tempe, who studies ancient human behavior at another South African cave (SN: 10/20/07, p. 243).
Even if the Blombos pigments contain intentional designs, fully modern human behavior — such as the use of figurative art (SN: 6/20/09, p. 11) — didn’t emerge until tens of thousands of years later, contends archaeologist Nicholas Conard of the University of Tuebingen, Germany.
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Henshilwood and study coauthor Francesco d’Errico of the University of Bordeaux I in Talence, France, disagree. In their view, the Blombos pigments bear intentionally fashioned designs that held some sort of meaning and were passed down the generations for 25,000 years. Thus, the two researchers say, it’s likely that a 100,000-year-old society already steeped in symbolic behavior originally produced the ochre engravings.
In 2002, Henshilwood’s team described evidence of symbolic engravings on two other ochre pieces from Blombos Cave. Those 77,000-year-old finds were excavated in 1999 and 2000.
Engraved chunks of pigment in the new analysis were unearthed during the same excavations. Specimens came from either of three sediment levels with estimated ages of 72,000 years, 77,000 years and 100,000 years.
A microscopic analysis indicates that ochre designs were made by holding a piece of pigment with one hand while impressing lines into the pigment with the tip of a stone tool. On several pieces, patterns covered areas that had first been ground down.
Geometric patterns on the ochre pieces include cross-hatched designs, branching lines, parallel lines and right angles.
Pigment powder had also been removed from many of the recovered ochre chunks. Incised patterns may have served as models for pigment designs applied to animal skins or other material, the scientists speculate.
Excavations of Blombos Cave sediment from before 100,000 years ago have begun. “The discovery of more, and perhaps even more striking, engravings is very possible,” Henshilwood says.