January 14, 2002
Volume 80, Number 2
CENEAR 80 2 p. 5
ISSN 0009-2347
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Artifacts push back date for human behavior that is considered modern


Two small carved pieces of rock excavated from a cave in South Africa suggest that humans began acting in ways considered modern much earlier than previously thought.

The inch-long pieces of red ochre were first ground to create a flat surface and then inscribed with a cross-hatched design. A team led by archaeologist Christopher Henshilwood of the South African Museum, Cape Town, and the State University of New York, Stony Brook, uncovered them in Blombos Cave, situated just above the Indian Ocean east of Cape Town. Thermoluminescence dating indicates the objects are at least 70,000 years old [Science, published Jan. 10, Science Express,].

STONE AGE ABSTRACT Engravings on ochre, at least 70,000 years old, suggest an early use of symbols. The Middle Stone Age inhabitants of Blombos Cave also left evidence that they fished in the nearby Indian Ocean.
These "two Blombos Cave ochres are the oldest known examples of engraved geometric designs," Henshilwood tells C&EN. "In essence, these indicate cognitive abilities associated with modern human behavior."

Anatomically modern human beings are thought to have arisen in Africa about 300,000 to 150,000 years ago. But when and where humans began to display modern behavior, including sophisticated use of tools and symbols, is a contentious issue. One school believes a "symbolic explosion" occurred roughly 40,000 years ago in Europe.

The Blombos excavations, however, support a much earlier appearance of modern behavior in Africa. In addition to the carved ochres, the site has yielded the oldest known bone tools and the earliest evidence for fishing ever discovered.

The ages of the Blombos objects were determined by dating minerals in the surrounding layer of sediment. One set of experiments, performed in the Luminescence Laboratory at the University of Wales, Aberystwyth, involved optically stimulated luminescence measurements of 1,800 individual sand-sized grains.

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