Stonehenge’s altar stone was carried all the way from north-east Scotland. But how?

Even by modern standards, John o’Groats to Wiltshire is a bit of a trek: nearly 500 miles, 13 hours by car or a 10-day walk – and that is without having a six-tonne block of stone in tow. So the revelation this week that Stonehenge’s altar stone came from the north-east of Scotland prompts the question of how on earth this feat was achieved more than 4,000 years ago.

“When you’re trying to move something weighing six tonnes in excess of 750km, it is an enormous undertaking,” said Prof Nick Pearce, a geologist at Aberystwyth University and the co-author of the research.

Even from its previously assumed origin of Wales, moving the megalith seemed such an arduous task that some academics proposed that it arrived in Wiltshire through a natural glaciation process.

Pearce said: “There’s been a lobby that argues that the stones were transported by ice to the area near Stonehenge and then picked up and used.” But this scenario excludes the revelation that the stone had a Scottish origin since the ice flow from the region was in a northerly direction. “From Orkney, I can’t see a way that the stone hikes a ride on half a dozen glaciers in the right order to end up on Salisbury plain.”

There is also evidence that the rocks were gouged out of the landscape rather than being serendipitous finds. “Based on our fieldwork in south-west Wales it is likely that the stone was extracted, rather than just lying loose on the surface,” said Prof Richard Bevins, also of Aberystwyth. Archaeologists have previously found stone wedges and hammerstones in the Preseli area of Wales that appear designed for such a task.

Bevins said: “The altar stone, which is a sandstone, has a natural plane of parting, which could be exploited in exactly the same way with rock wedges and hammerstones, enabling extraction of a large slab-like rock piece.”

The next job would have been hoisting the stone off the ground, which is less difficult than it sounds, according to Julian Richards, an archaeologist and TV presenter. This is based on his own experience of raising a 12-tonne cap stone off a neolithic tomb during a visit to Cornwall a few years ago. “I had underestimated the weight of it, but we just got that off the ground with a series of wooden levers,” he said. “Lifting it is not a problem, but moving it is.”

From there, Richards speculates, the stone may have been lashed on to a wooden sledge and pulled along logs arranged like railway sleepers using ropes made from plant fibres. “You can make good ropes out of things like lime bark,” he said. “It produces very strong, long fibres that can be woven into ropes that would be capable of moving something of this sort of scale.”

Experts are divided on whether land or sea is a more likely option for the stone’s onward journey.

“My gut feeling is that it came over land and it possibly took a long time and was not necessarily in one fell swoop,” said Heather Sebire, a senior curator at English Heritage. “Getting places as quickly as possible is a modern concept – we’re always in a hurry. Their mindset was probably very different. You can think of it as a pilgrimage.”

The terrain would have been challenging, Sebire said, but the idea the entire British Isles were covered in dense forest is a myth. “Near Stonehenge it would have been open scrub with clusters of trees,” she said. “If they literally went from A to B it could have been months or it could have taken years.”

Sebire is also swayed by a lack of archaeological evidence for advanced neolithic boats. “Experiments have been done trying to bring the equivalent of the bluestones on rafts across the Severn,” she said. “I’m afraid none of them have been successful. They sank.”

Richards is more enthusiastic about the possibility of a sea voyage, based in part on a re-enactment experiment of his own in which 140 people attempted to move a 40-tonne block of concrete. “We didn’t move it very far. Actually getting a team of people together and coordinating them is quite difficult.”

This may have played to the strengths of neolithic communities, for whom teamwork would have been an inherent part of day-to-day survival. “These people were used to moving big stones,” said Richards. “When you see people who are used to moving stuff they make it look easy. We underestimate their inherent skill and experience.”

He estimates that 40 to 50 people might have been required to lug the altar stone, but questions whether even a strong, cohesive team would have been able to carry it over hills and around mountains. And although no sophisticated vessels have been discovered, there is evidence for a trade in stone axes between the Alps and the Lake District, pottery in the south of England that had origins in Orkney and of herds of cattle being transported across the Channel. “This idea that everyone lived in little isolated groups is not right,” said Richards.

Conclusive evidence about the altar stone’s route may remain out of reach, but experts agree that the journey is further evidence of the neolithic builders’ ingenuity. “Those people were just the same as us,” said Sebire. “They were just as clever and as enterprising and they had the brain power.”