Shell beads point to dawn of modern human behaviour
25 August 2009
We often judge other people based on material possessions - the clothes we wear and the things we own can advertise our wealth, status and social allegiances. But when did we start using our belongings to tell others about ourselves?
Nassarius shells. Copyright: d'Errico/ Vanhaeren.
A new study by an international team of researchers from France, South Africa, Germany, Israel and the UK has confirmed that 80,000-year-old shell beads found in caves in North Africa represent some of the earliest evidence of the use of personal ornamentation.
The new research shows the shell beads were common across North Africa until they fell out of use around 70,000 years ago. Previously, the shells were known from only a few scattered examples. 'We are no longer looking at isolated or one off events.' says Professor Nick Barton of the University of Oxford, one of the authors of the study. 'We can now document the shells at a number of different locations in North Africa all of about the same age' he adds.
The beads provide evidence that the people alive at the time were acting much like modern humans. 'There is a problem with linking anatomically modern humans with behaviourally modern humans,' Barton explains. 'These people may have looked like us, but were they behaving the same?' he adds.
The presence of the beads suggests the people who made and wore them behaved in ways we would recognise. Using symbolic items like shell beads to communicate ideas about the wearer requires skills found only in modern humans, including a well-developed language and the ability to use abstract concepts.
The researchers analysed 25 beads from four sites in North Africa from the Middle Palaeolithic period. The beads, consisting of the shells of sea snails called Nassarius, had been transported some distance from the marine environment in which they're usually found, and showed evidence of deliberate alterations.
'We found evidence they had been strung together as in a necklace or bracelet,' said Barton. The shells had been deliberately perforated using stone tools and the researchers found distinctive wear patterns which suggested they had been rubbing together. Wear marks around the perforations indicated the shells had been threaded on a string. Several had also been covered with a pigment called red ochre and one shell showed evidence of heating, possibly to alter its colour.
The origins of fashion?
But what purpose did the coloured beads serve? 'What they were signalling, we're not entirely sure.' said Barton. 'Possibly they were an insurance policy, if you had shared access to certain resources and wanted to identify yourself to members of another group.' The beads may also have let wearers identify members of the same social group, preventing unnecessary conflicts.
Alternatively, the beads might have provided personal information about the wearer, such as the wearer's position in the social hierarchy, or that they had passed through puberty and into adulthood.
So do these beads represent the origins of today's fashions? Possibly not, according to the researchers. There is a gap in the archaeological record starting 70,000 years ago, during which no personal ornaments are found. They reappear around 20,000 years later, when humans are beginning to move out of Africa to colonise the rest of the world.
The researchers suggest the gap was due to climate change. As the world slid into another ice age the warm, humid North African climate dried out. As a result, human populations shrank, and cultural innovations such as shell beads may have been lost. Only with the expansion of the human population 20,000 years later were these cultural ideas rediscovered.
The work was partly supported through the RESET (Response of Humans to Abrupt Environmental Transitions) programme, which seeks to examine how climate change affected the evolution and adaptation of our ancestors.
The research was published in the journal Proceedings of the National Academy of Science.
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