The prehistoric monument Stonehenge, near Amesbury in southern England, has long fascinated researchers and visitors.
Daniel Leal/AFP via Getty Images
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Daniel Leal/AFP via Getty Images
Researchers say they have traced the origins of Stonehenge’s so-called “Altar Stone”, the monolith at the heart of one of the world’s most mysterious monuments.
The purpose of this prehistoric structure in southern England has long been a mystery, although in recent years scientists have been able to determine where most of the structure’s stones came from: The upright sarsen stones were found in the nearby Marlborough Downs area of England, while the smaller bluestones originated in southwest Wales.
“The Altar Stone is the last remaining stone,” said Anthony Clarke, a PhD student at Australia’s Curtin University and lead author of the book. a new study about the stone’s origins was published this week in the journal Nature.
Clarke, who studies geochronology (the science of determining the age of rocks), has always been particularly fascinated by Stonehenge—he grew up on a farm in southwest Wales, where some of the stones are located.
The six-ton Altar Stone itself — now lying broken on the ground, partly covered by two other stones believed to have collapsed — has long been thought to have come from South Wales, but research published last year really rule out that possibility.
Clarke corresponded via email with Nick Pearce, one of the Aberystwyth University researchers who worked on that study, and accepted an offer to send some Altar Stone samples for analysis.
The Altar Stone, seen here below two larger Sarsen stones.
Nick Pearce/Aberystwyth University
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Nick Pearce/Aberystwyth University
Clarke explains that this involves examining the age and chemical characteristics of the individual mineral grains that come together to form the sandstone.
“When you get this profile — this fingerprint, in a way — of the rock, we can do forensic comparisons with potential source areas around the UK,” he said. “And when we do that … it looks very similar to the Orcadian Basin sedimentary rocks.”
That’s surprising, in no small part because the Orcadian Basin is located in northeastern Scotland — more than 450 miles from the site of Stonehenge.
“When we first got that first batch of data, I looked at it and said, ‘There’s no way this could be so specific to Scotland,’” Clarke added. “So we did more analysis… and time and time again, it was clearly not from southern England, and it turned out to be from this Orcadian basin. It was remarkable.”
Stone’s Stone Age Journey May Be Evidence of High Level of Social Organization
The findings suggest that the approximately 12,000-pound, 16-foot-long stone somehow traveled hundreds of miles from Scotland to England. before invention of the wheel. (Archaeologists suspect it was installed at Stonehenge sometime between 2620 BC and 2480 BC)
As Clarke says, just driving from northern Scotland to England is quite an arduous journey these days.
“Think of our Neolithic ancestors, with their landscape of forests, rivers, swamps and mountains — it would have been terrifying, if not impossible,” he added.
It is unclear why the stone was carried so far, or how long it took. But there are several theories about how it made the journey.
One is that giant ice walls carried rocks south, but Clarke says ice sheet reconstructions show they actually moved rocks in the opposite direction.
He and other researchers believe the most likely explanation is that it was brought to Britain by boat, especially since there is evidence of a Neolithic maritime trade network involving things like tools and livestock. If so, he said, it would indicate a “fairly advanced and skilled society”.
“Such a route demonstrates a high level of social organization with inland transport activities in Britain during the Neolithic period,” the team’s study said.
The six researchers, based in Australia, Wales, and England, spent years working together online on this study. They only met in person for the first time this week — at Stonehenge, of course.
Lead author Anthony Clarke poses for a photo in his lab at Curtin University in Perth, Australia.
Curtin University
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Curtin University
“I guess it’s weird when you’ve been talking to people through a screen for years and then you finally meet them and you’re here, in this very special place,” Clarke said. “And the mist is rolling in over the hills, and it’s very quiet and cold, and it’s quite a surreal experience.”
While the exact details of the Altar Stone’s journey may be lost to time, the findings raise many other questions about the era in which it emerged — some of which future archaeologists hope to be able to answer, Clarke said.
Meanwhile, Clarke, 26 and completing his PhD, will turn his attention to the many other tools and stones—whether at Stonehenge or beyond—that still need to be tracked down. He explains that dating geological material can help better understand human history.
“A human lifetime is 100 years. But the Altar Stone has been there for thousands of years, the particles inside the Altar Stone have been there for many orders of magnitude more, 3,000 million years,” he added. “It’s just the idea of time and adding pages to the history of the Earth.”
