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3 months ago
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How neolithic humans might have transported so many huge boulders from Wales to Stonehenge is one of archaeology's most enduring mysteries.
However, a new study of a 'lost' boulder taken from the Stonehenge site over 90 years ago suggests that humans might not have moved the stones at all.
Dr Brian John, a retired geology lecturer from Durham University, argues that this bluestone boulder bears marks which suggest it was moved by glacial ice.
This would undermine the common theory that the bluestone was quarried in the Preseli Hills of southwest Wales and manually transported to the Salisbury Plain.
Speaking to MailOnline, Dr John said: 'I think it's hugely significant because it supports the assumption I've had for some years that these are not humanly-transported.'
A new assessment of a 'lost' boulder from Stonehenge suggests that the site's massive stones might not have been transported by humans
The Newall Boulder (pictured) was almost forgotten for over 90 years, but now research suggests it may have been carried to Stonehenge from Wales by ice
In addition to the tall Sarsen stones that make up Stonehenge's distinctive appearance, the site is also home to around 80 smaller bluestones.
It is generally agreed that these stones originate from the Preseli Hills of south-west Wales, but how they got to Stonehenge is often debated.
Dr John's argument centres on an analysis of a bluestone boulder about the size of a human skull, known as the Newall boulder.
This boulder was first excavated in 1924 by the geologists Colonel Hawley and Robert Newall.
Hawley originally thought the rock was just a piece of rubbish and wanted to throw it away rather than analyse it.
However, Newall saved the stone from the rubbish heap and placed it in a cardboard box in his attic alongside a number of other finds from the site.
Stonehenge is a prehistoric megalithic structure on Salisbury Plain in Wiltshire, England, two miles (3 km) west of Amesbury
Dr Brian John, a retired geology lecturer from Durham University, argues that this bluestone boulder bears marks which suggest it was moved by glacial ice
The boulder remained there until Newall passed it over to the Salisbury Museum shortly before he died in 1976.
There was a brief burst of interest in the boulder around 1977 - but then it was placed back into storage and effectively forgotten for another 46 years.
However, in 2022, Dr John found a reference to the boulder and asked the Museum Director Adrian Green if it was still in storage.
On discovering that it was, he was given permission to examine it and undertake a careful examination of its surface features.
Through a detailed analysis of the boulder's surface, Dr John identified a series of marks that suggest glacial, rather than human transport.
'Glacially transported boulders tend to have facets,' Dr John explains.
'That means they've got a number of different faces at angles to one another which actually indicated where a boulder has been abraded or, basically, sanded down.'
As boulders move with a glacier they get flipped over from side to side, creating several different flat faces with rounded edges, just like the Newall boulder.
The findings suggest that the 80 or so bluestone boulders at Stonehenge may all have been carried to the site by ice and not by Neolithic builders
In addition, the boulder bears a series of scratches and small fractures, called striations and chattermarks, which are often caused by glacial transport.
And although the Newall Boulder isn't exactly the same type of rock as the other bluestones, Dr John says this is exactly what his theory would predict.
He says: 'It's often claimed in popular articles that the bluestones are all made of spotted dolerite which is this type of igneous rock we get on the Preseli Hills but they're actually about 30 different rock types.
'That enormous range of rock types is absolutely typical of the way that ice travels across the terrain and picks up boulders from here there and everywhere.'
Dr John says these bluestones (pictured) are far too weathered and rough to have been quarried and transported
Dr John suggests that this provides convincing evidence that the Newall boulder and all of the smaller bluestone boulders at Stonehenge were moved by glacier.
His claims land him squarely at the centre of one of the Stonehenge's contentious debates.
The idea that the stones were transported to Salisbury Plain began with the geologist Herbert Henry Thomas in 1923.
Although Thomas was quite spectacularly wrong about almost everything, the human transport theory is still extremely popular.
The bluestone boulders may have been carried from Wales to the Salisbury Plain by a combination of Welsh and Irish ice
A team of researchers led by Professor Mike Parker Pearson of UCL have been some of the most active proponents of this theory, arguing that the stones were moved over land.
Recently, Professor Pearson and his team even claimed to have discovered evidence which identifies the quarry of the Stonehenge bluestone, dating this to 3000 BC.
However, Dr John now says his discovery should 'open up the debate' for a consideration of other theories.
He says: 'Herbert Thomas thought that because glacial transport was impossible they must have been carried by human beings.
'That's now part of our national myth because people have not seriously questioned it before; it's just been accepted as the truth.'
This map shows the variety of stones present in Southwest Wales. Dr John says the variety of bluestone types matches how a glacier would gather up stones from lots of different places
Instead of the orderly and rather deliberate building project we sometimes imagine Stonehenge to be, Dr John says: 'I think its always been a bit of shambles.'
He argues that the Neolithic builders simply used the stones they had in their immediate vicinity, rearranging and moving the smaller bluestones as needed.
And, when they eventually had to travel too far to gather more stones, the project was simply abandoned in the state we now find it.
'It was a Neolithic cost-benefit analysis that eventually the costs of getting the stones were were greater than the benefits that were coming from it,' he says.
This suggestion could overturn the prevailing theory that the Stonehenge bluestones (pictured and numbered) were transported over land by humans
However, the ultimate test for his theory would be cosmogenic dating - a test to determine how long rocks have been exposed to the surface by measuring their exposure to cosmic rays.
If Dr John is right, the deeply weathered surface of the rocks should have been exposed to the elements for hundreds of thousands of years.
Alternatively, if the stones were quarried they should only have been exposed to cosmic radiation for around 3,000 to 5,000 years.
While the debate over the origin of the stones is still very much alive, Dr John believes the evidence of weathering will remain strong.
He concludes: 'I'm very confident that if one or other university can get its act together and actually get this done these stones will be seen to have been subject to cosmogenic bombardment from the atmosphere for possibly for hundreds of thousands of years.
'That would knock the quarrying idea on its head once and for all.'
