Evidence that bluestones were quarried in Wales 500 years before they were put up in Wiltshire prompts theory that Stonehenge is ‘second-hand monument’

Evidence of quarrying for Stonehenge’s bluestones is among the dramatic discoveries leading archaeologists to theorise that England’s greatest prehistoric monument may have first been erected in Wales.

It has long been known that the bluestones that form Stonehenge’s inner horseshoe came from the Preseli hills in Pembrokeshire, around 140 miles from Salisbury Plain.

Now archaeologists have discovered a series of recesses in the rocky outcrops of Carn Goedog and Craig Rhos-y-felin, to the north of those hills, that match Stonehenge’s bluestones in size and shape. They have also found similar stones that the prehistoric builders extracted but left behind, and “a loading bay” from where the huge stones could be dragged away.

Carbonised hazelnut shells and charcoal from the quarry workers’ campfires have been radiocarbon-dated to reveal when the stones would have been extracted.

Prof Mike Parker Pearson, director of the project and professor of British later prehistory at University College London (UCL), said the finds were “amazing”.

“We have dates of around 3400 BC for Craig Rhos-y-felin and 3200 BC for Carn Goedog, which is intriguing because the bluestones didn’t get put up at Stonehenge until around 2900 BC,” he said. “It could have taken those Neolithic stone-draggers nearly 500 years to get them to Stonehenge, but that’s pretty improbable in my view. It’s more likely that the stones were first used in a local monument, somewhere near the quarries, that was then dismantled and dragged off to Wiltshire.”

Facebook Twitter Pinterest Stonehenge on Salisbury Plain. Photograph: UCL

The dating evidence suggests that Stonehenge could be older than previously thought, Parker Pearson said. “But we think it’s more likely that they were building their own monument [in Wales], that somewhere near the quarries there is the first Stonehenge and that what we’re seeing at Stonehenge is a second-hand monument.”

There is also the possibility that the stones were taken to Salisbury Plain around 3200 BC and that the giant sarsens – silicified sandstone found within 20 miles of the site – were added much later. “Normally we don’t get to make that many fantastic discoveries in our lives,” Parker Pearson said. “But this is one.”

Parker Pearson heads a project involving specialists from UCL and the universities of Manchester, Bournemouth and Southampton, among others. Their findings are published on Monday in the journal Antiquity alongside a new book by the Council for British Archaeology titled Stonehenge: Making Sense of a Prehistoric Mystery.

Prof Kate Welham, of Bournemouth University, said the ruins of a dismantled monument were likely to lie between the two megalith quarries. “We’ve been conducting geophysical surveys, trial excavations and aerial photographic analysis throughout the area and we think we have the most likely spot. The results are very promising. We may find something big in 2016,” she said.

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The long-distance transport of the bluestones from Wales to Stonehenge is one of the most remarkable achievements of Neolithic societies. The archaeologists estimate that each of the 80 monoliths weighed less than two tons and that people or oxen could have dragged them on wooden sledges sliding on rail-like timbers.

Parker Pearson said people in Madagascar and other societies were known to have moved such standing stones long distances and that doing so created a spectacle that brought together communities from afar.

“One of the latest theories is that Stonehenge is a monument of unification, bringing together people from across the many parts of Britain,” he said.

He recalled the moment he looked up the near-vertical rock-face and realised that this was one of the quarries. “Three metres above us were the bases of these monoliths that were actually sitting there ready simply to be lowered out of their recesses,” he said.

“It’s the Ikea of Neolithic monument building. The nice thing about these particular outcrops is that the rock has formed 480m years ago as pillars. So prehistoric people don’t have to go in there and bash away … All they have to do is get wedges into the cracks. You wet the wedge, it swells and the stone pops off the rock.”