In brief: Stonehenge is easily the oldest and most mysterious of Britain's iconic monuments. Its true purpose might never be definitively uncovered, but researchers continue to infer details regarding when and how it was constructed. A new study suggests that a central component of the structure originated on the opposite end of Great Britain, implying a high degree of sophistication in the societies that built it.
A paper recently published in the scientific journal Nature presents evidence that the altar stone at the center of Stonehenge was transported to the site from northeastern Scotland, over 460 miles away. If the study's assertions are accurate, then the stone is by far the megalith's most exotic component.
Upon analyzing fragments of the altar stone, a large slab that lies flat underneath other collapsed stones, researchers discovered that its composition closely matches Old Red Sandstone from the Orcadian Basin in northeast Scotland. The study's authors theorize that the 13,000-pound rock was transported by sea to the site of Stonehenge in southern England.
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Observers have long understood that the monument could only have been created by complex cultures capable of coordinating large construction projects and sourcing materials from far away. The bluestones, which form a circle in the interior, likely came from southern Wales, over 100 miles away. Still, a Scottish origin for the altar stone defies prior knowledge about Stonehenge's origins.
The UNESCO World Heritage Site was built in stages by multiple groups of people over around 2,000 years. The area had been important to Mesolithic hunter-gatherers since roughly 8,000 BC, but Neolithic farmers likely created the initial earthen ditches surrounding the site sometime around 3,000 BC.
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A circle of local sarsen stones and Welsh bluestones was erected within the earthen ring around 2,500 BC (roughly the same time the Egyptian pyramids were built), with the altar stone roughly at its center. They were probably rearranged in the 2,200s BC, and the site remained in use until around 1,500 BC. Parts of the structure are carefully aligned so that the sun lights them during the summer and winter solstices.
Whoever constructed Stonehenge shaped the rocks into their current form and used indentations to lock them into place. The achievement is particularly impressive because the builders would've only had access to stone-age tools and would not have possessed the wheel.