Stonehenge in Wiltshire, southern England, is a mysterious place that speaks of a culture and political–religious authority of which we know almost nothing, probably motivated by belief in long-dead gods whose supposed presence was, at the time, undoubtedly considered to be “all around”. This is much as theists of all religions assert of their god or gods today. Who these people were, remains one of the great mysteries, as does how they moved such massive stones into place to build a stone circle with extraordinary precision, and how they transported them over long distances long before the domestication of the horse.
We know they were not the later Welsh-speaking Celts, who did not arrive in Britain until around 1,000 BCE — some two millennia after construction of Stonehenge began. Those Celts replaced the Beaker culture, which itself had replaced the Neolithic farming communities who first built the monument. Construction began around 3,000 BCE, initially as a bank-and-ditch enclosure with a circle of wooden posts. This was later replaced, around 2,500 BCE, by a circle of massive sarsen stones sourced locally from the nearby Salisbury Plain, with the smaller bluestones brought from the Preseli Hills in south-west Wales. The so-called “altar stone” was added last. Its precise origin remains unresolved, with conflicting evidence suggesting either north-west Scotland or west Wales as its source.
While the question of where most of the stones came from has largely been resolved, what remains is the long-standing puzzle of how they were transported using only human labour. The motivation was clearly strong enough to justify the immense effort and manpower involved, and the fact that it was human effort that moved them has now been established beyond reasonable doubt by the falsification of an alternative hypothesis — namely, that the stones were carried to Salisbury Plain by a passing glacier during the last Ice Age.
The refutation of this idea provides a neat example of how science tests and falsifies hypotheses, though it will no doubt unsettle creationists who cling to the absurd belief that the entire history of the Earth can be compressed into a timescale of just 6,000–10,000 years. The work was carried out by two researchers from Curtin University in Perth, Western Australia, and relied on dating zircon crystals — a highly accurate method for determining the age of rock formations, as regular readers of this blog will know — along with apatite grains, which similarly exploit the radioactive decay of uranium isotopes into stable lead isotopes.
How this was done is explained in an article published in The Conversation by the two scientists involved: Anthony Clarke, Research Associate in the School of Earth and Planetary Sciences at Curtin University, and Chris Kirkland, Professor of Geochronology at Curtin University. Their article is reprinted here under a Creative Commons licence, reformatted for stylistic consistency.
Grains of sand prove people – not glaciers – transported Stonehenge rocks
Dr Anthony Clarke at Stonehenge
Anthony Clarke, Curtin University and Chris Kirkland, Curtin University
Ask people how Stonehenge was built and you’ll hear stories of sledges, ropes, boats and sheer human determination to haul stones from across Britain to Salisbury Plain, in south-west England. Others might mention giants, wizards, or alien assistance to explain the transport of Stonehenge’s stones, which come from as far as Wales and Scotland.
But what if nature itself did the heavy lifting in transporting Stonehenge’s megaliths? In this scenario, vast glaciers that once covered Britain carried the bluestones and the Altar Stone to southern England as “glacial erratics”, or rocks moved by ice, leaving them conveniently behind on Salisbury Plain for the builders of Stonehenge.
This idea, known as the glacial transport theory, often appears in documentaries and online discussions. But it has never been tested with modern geological techniques.
Our new study, published today in Communications Earth and Environment, provides the first clear evidence glacial material never reached the area. This demonstrates the stones did not arrive through natural ice movement.
While previous research had cast doubt on the glacial transport theory, our study goes further and applies cutting-edge mineral fingerprinting to trace the stones’ true origins.
A reconstruction of the stones being moved at Stonehenge.
Image: Bradshaw Foundation
Giant ice sheets are messy, leaving behind piles of rock, scratched bedrock and carved landforms.
However, near Stonehenge, these tell-tale clues are either missing or ambiguous. And because the southern reach of ice sheets remains unclear, the glacial transport idea is open to debate.
So, if no big and obvious clues are present, could we look for tiny ones instead?
If glaciers had carried the stones all the way from Wales or Scotland, they would also have left behind millions of microscopic mineral grains, such as zircon and apatite, from those regions.
When both minerals form, they trap small amounts of radioactive uranium – which, at a known rate, will decay into lead. By measuring the ratios of both elements using a technique called U–Pb dating, we can measure the age of each zircon and apatite grain.
Because Britain’s rocks have very different ages from place to place, a mineral’s age can indicate its source. This means that if glaciers had carried stones to Stonehenge, the rivers of Salisbury Plain, which gather zircon and apatite from across a wide area, should still contain a clear mineral fingerprint of that journey.
Searching for tiny clues
To find out, we got our feet wet and collected sand from the rivers surrounding Stonehenge. What we discovered was striking.
Despite analysing more than seven hundred zircon and apatite grains, we found virtually no mineral ages that matched the bluestone sources in Wales or the Altar Stone’s Scottish source.
Zircon is exceptionally tough: grains can survive being weathered, washed into a river, buried in rocks, and recycled again millions of years later. As such, zircon crystals from Salisbury Plain rivers span an enormous stretch of geological time, covering half the age of the Earth, from around 2.8 billion years ago to 300 million years ago.
However, the vast majority fell within a tight band, spanning between 1.7 and 1.1 billion years old. Intriguingly, Salisbury River zircon ages match those from the Thanet Formation, a blanket of loosely compacted sand that covered much of southern England millions of years ago before being eroded.
This means zircon in river sand today is the leftovers from ancient blankets of sedimentary rocks, not freshly delivered sand from glaciers during the last Ice Age 26,000 to 20,000 years ago.
Apatite tells a different story. All grains are about 60 million years old, at a time when southern England was a shallow, subtropical sea. This age doesn’t match any potential source rocks in Britain.
Instead, apatite ages reflect the squeezing and uplifting caused by distant mountain-building in the European Alps, causing fluids to move through the chalk and “reset” apatite’s uranium-lead clock. In other words, the heating and chemical changes erased the mineral’s previous radioactive signature and started the clock ticking again.
Much like zircon, apatite isn’t a visitor brought in by glaciers but is local and has been sitting on Salisbury Plain for tens of millions of years.
A new piece of the Stonehenge story
Stonehenge sits at the crossroads of myth, ancient engineering and deep-time geology.
The ages of microscopic grains in river sand have now added a new piece to its story. This gives us further evidence the monument’s most exotic stones did not arrive by chance but were instead deliberately selected and transported.
Anthony Clarke, Research Associate, School of Earth and Planetary Sciences, Curtin University and Chris Kirkland, Professor of Geochronology, Curtin University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Publication:
What makes this work particularly instructive is not simply that it resolves a long-running archaeological question, but that it demonstrates, in miniature, how science actually works. Competing hypotheses were proposed, evidence was gathered, and one explanation — glacial transport — failed the test. It was not rejected because it was unfashionable or ideologically inconvenient, but because the physical evidence preserved within the stones themselves does not support it. The conclusion that human beings moved these stones is therefore not an assumption, but what remains after alternative explanations were eliminated.
Crucially, the researchers were able to falsify the glacial hypothesis directly by dating zircon grains contained within the stones. These zircons were shown to be hundreds of millions, and in some cases billions, of years old, recording geological histories far older than anything that could plausibly have been deposited during the last Ice Age. Had the stones been carried to Salisbury Plain by glacial action, their zircon populations would reflect a much more recent and uniform provenance. Instead, they preserve complex thermal histories that are incompatible with Ice Age transport and entirely consistent with deliberate human movement by human communities.
That result sits very uncomfortably alongside creationist claims that the entire history of the Earth can be compressed into a few thousand years. The radiometric techniques used here are neither exotic nor controversial; they are the same well-established methods employed across geology, planetary science, and archaeology worldwide. They consistently point to deep time — a planet shaped by processes operating over hundreds of thousands and millions of years — and they do so independently of any narrative about Stonehenge itself. The monument merely provides another clear, tangible example of evidence refusing to conform to dogma.
Stonehenge, then, is mysterious only in the human sense. We may never know precisely what it meant to those who built it, or which gods, spirits, or social obligations motivated such extraordinary effort. What is no longer mysterious is the framework in which it belongs. It was constructed by real people, using ingenuity, organisation, and labour, within a world governed by physical laws that leave measurable traces behind. Those traces allow us to test ideas, discard the wrong ones, and move closer to the truth — a process that stands in stark contrast to belief systems that demand certainty while offering none of the evidence required to justify it.
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