CAVE dwellers used mollusc shells to make jewellery at least 75,000 years ago. This discovery of Stone Age shell beads is the best evidence yet that people had advanced concepts of symbolism and language so long ago.
There are two competing theories for how modern human behaviour emerged. One is that it evolved abruptly in Africa or Eurasia some 40,000 to 50,000 years ago. The other suggests it emerged gradually in Africa between 50,000 and 250,000 years ago.
The recent discovery of two small, clearly decorative beads made of ostrich eggshell in the Loiyangalani river valley in Tanzania had suggested the second theory was more likely. The beads seemed to be between 45,000 and 110,000 years old, and plants found at the site suggest the older end of that range. But archaeologists have been cautious as no one can yet be certain of the site’s age (91av, 10 April, p 8).
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Now more conclusive evidence has emerged from a study of Stone Age shells from the gastropod Nassarius kraussianus. Several clusters of the shells have turned up since 1997 in excavations at Blombos cave at the southern tip of South Africa. They are about the size of peas, and have a hole punched in them, almost always in the same position. The shells come from a layer of sand about 75,000 years old.
Christopher Henshilwood of the University of Bergen in Norway and his colleagues analysed 41 of the shells, which were found in clusters of similar shade and size. They contain traces of ochre, which Stone Age cave dwellers reputedly used as a decorative pigment.
Under the microscope, the team found slightly worn, smoothed regions near the mouths of the shells and the pierced holes. These worn patches, which are not normally found on shells, are consistent with the idea that they rubbed against thread, clothes or other shells (Science, vol 304, p 404).
That is compelling evidence that the cave dwellers deliberately pierced the shells so they could string them together into necklaces or bracelets, says Henshilwood. Blombos cave is famous for its abstract engravings on ochre from the same time period, and together with the beadwork, this suggests to Henshilwood that its inhabitants had a complex sense of symbolism.
To communicate the meaning of the symbols, Henshilwood believes the society must also have had well-developed language with some kind of grammatical structure. “They must have had a way of describing the symbolic message that the beads represent,” he says.