January 10, 2002 -- People were able to think abstractly, and accordingly behave as modern humans much earlier than previously thought, according to a paper appearing in this week's issue of Science.
Christopher Henshilwood, adjunct professor at the State University of New York, Stony Brook, and the Iziko South African Museum in Cape Town and his team found abstract representations of two pieces of ochre, two and three inches long. The objects, dated to at least 70,000 years ago, were recovered from the Middle Stone Age layers at Blombos Cave, a site on the southern Cape shore of the Indian Ocean 180 miles east of Cape Town, South Africa. Henshilwood's work at the cave is supported by the National Science Foundation (NSF).
The earliest previous evidence of abstract representations is from the Eurasian Upper Paleolithic period mainly in France and dated to less than 35,000 years ago.
Ochre, a form of iron ore, is frequently found in stone age sites deposits less than 100,000 years old and may have been used symbolically as a body or decorative paint and possibly also for skin protection and tanning animals' hides.
Rather than being outlines of animals or other representations drawn from nature, the designs on the two pieces of ochre show a consistent representation of the development of arbitrary conventions to express mutually understood concepts. "They may have been constructed with symbolic intent, the meaning of which is now unknown," Henshilwood said.
"These finds demonstrate that ochre use in the Middle Stone Age was not exclusively utilitarian and, arguably, the transmission and sharing of the meaning of the engravings relied on fully syntactical language," he added.
The two pieces of ochre were first scraped and ground to create flat surfaces. They were then marked with cross hatches and lines to create a consistent complex geometric motif. The discovery adds important new insights to understanding the development of humans, who are known to have been anatomically modern in Africa about 100,000 years ago.
Scholars are not yet able to determine if behavior and physique developed in tandem. They also do not agree entirely on what behavior traits best define the difference between modern humans and their earlier ancestors. "There is agreement on one criteria-archaeological evidence of abstract or depictional images indicates modern behavior. The Blombos Cave engravings are intentional images," Henshilwood said.
Blombos Cave is a rich site that has yielded early evidence of bone tool manufacture and fishing, both also widely regarded as markers of modern human behavior. The ochre pieces were found in 1999 and 2000 and both were located close to hearths and in an undisturbed deposit of ash and sand.
In order to determine the age of the ochre pieces, two state of the art luminescence-based dating methods were applied by dating teams from Wales and France. One method dates the sand grains that lie above the ochre and the second dates burnt stone found in the same layer as the engraved ochres.
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