Scotland's 5,000-year-old carved stone balls shrouded in mystery

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More than 500 of these 5,000-year-old carved stone balls have been discovered, mostly in Scotland, but their purpose remains a mystery.
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Featuring knobs and intricate markings of spirals and lines, these stone balls date back to around 3,200 BC to 2,500 BC.
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The Towie ball, seen here as a 3D image, is perhaps the most beautiful example. It is on display at the National Museums Scotland, in Edinburgh.
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Some of the balls were found in the remarkably preserved Neolithic settlement of Skara Brae, in the Orkney Islands, off the northern coast of Scotland.
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The carved stone balls were created during an era when people transitioned from hunter gatherers to farmers, in settlements such as Skara Brae.
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To gain a better understanding of the carved stone balls, and to bring the collection closer to the public, Hugo Anderson-Whymark, curator of National Museums Scotland, created 3D images of 60 balls from the museum's collection.
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Using a technique called photogrammetry, Anderson-Whymark took hundreds of 2D images from every angle to create very detailed 3D renderings of the stone balls. The resulting 3D images revealed previously unseen details in the design.
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For instance, this 3D image of a carved stone ball from Buchromb, Banffshire, showed evidence that the large knob was reworked into smaller ones over time, suggesting a process of modification that was not known before the 3D images were made.
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