A new study published in the Journal of Archaeological Science offers fresh insight into a longstanding mystery surrounding Stonehenge.

Located on Salisbury Plain in Wiltshire, this iconic prehistoric structure includes a perplexing rock known as the "Newall boulder." For years, scientists have debated whether this boulder was transported to Stonehenge by Welsh glaciers or by human hands over 5,000 years ago.

Professor Richard Bevins and his team at Aberystwyth University recently compared the Newall boulder with samples from a rocky outcrop at Craig Rhos–y–Felin in Wales. Using advanced microscopic and geochemical techniques, they found "no evidence to support the idea that it is a glacial erratic."

Instead, the stone matched the characteristics of rocks from Craig Rhos–y–Felin, indicating that it was likely carried over 125 miles by humans to Wiltshire. Chemical analysis revealed that the boulder and other fragments from Stonehenge share identical amounts of thorium and zirconium, aligning with the geology of Craig Rhos–y–Felin.

The researchers noted that the boulder is a foliated rhyolite, with a surface layer rich in calcium carbonate, further supporting the hypothesis that humans transported it. Glaciers, they argued, would have distributed similar stones across the region, making it unlikely that the boulder was a product of glacial movement.

Another stone at the site, Stone 32d, was also studied. Previously thought to be a spotted dolerite, it was found to be a foliated rhyolite, just like the Newall boulder.

"Part of the fascination of Stonehenge is that many of its megaliths, in contrast to the larger, more locally sourced sarsens, can be traced back to Wales, over 200 kilometers away," the research team explained.

"Most archaeologists agree that Neolithic people managed this impressive feat of transporting stones weighing up to 3.5 tonnes. However, there is an opposing view, which suggests that no human effort was involved. This theory argues that the Welsh stones were carried by glacial ice long before Stonehenge was constructed." One of the strongest proponents of the glacier theory is Dr. Brian John.

Dr. John had previously argued that the boulder was reduced in size and significantly altered during glacial transport, possibly sitting on the bed of a glacier for much of the journey before being deposited on or near Salisbury Plain. However, the new research suggests these features might be the result of weathering rather than glacial activity.

The researchers stated that presenting Dr. John’s theory as fact, rather than a hypothesis, is misleading. "The presence of Stonehenge itself is evidence that Neolithic people moved stones weighing up to 40 tonnes. Unless one argues that the stones were simply lying on the ground ready to be set up, it is clear that the stones must have been moved into place."

"If Neolithic people were capable of moving stones a few tens of meters, they could certainly move them hundreds of kilometers," the study concluded. "Though it may not have been easy, it was entirely feasible, and moving 2–3 tonne bluestones would require far less effort than moving the sarsens."

While the exact methods of transport remain unknown, the study points out that recent indigenous peoples have successfully moved large stones across great distances using ropes, wooden sledges, and trackways—technologies that would have been available to Neolithic people.