The origin of Stonehenge has given archeologists sleepless nights for nearly 100 years. In 1923, geologist Herbert Henry Thomas famously argued that the 2-3 ton bluestones of the rock megalith originated in the Mynydd Preseli area of coastal south Wales. But how would a bunch of Stone Age builders have hauled these vast rocks to Salisbury in southern England from the coast of Wales? Building on the theory posed by H.H. Thomas, many have suggested that the bluestones were transported via the sea from Mynydd Preseli down the Welsh coast until they hit current-day Bristol.

Not so, says new research. Publishing their research in the journal Antiquity, archaeologists from the University of Leicester argue that the highly influential work of Thomas was based on poor evidence.

Stonehenge was built by a mysterious group of ancient people in several stages over the centuries, the first of which was a basic monument that was built sometime after 3,000 BCE. There are two types of stone at Stonehenge, the smaller “bluestones” and the more iconic large slabs of sarsen stones. Radiocarbon dating suggests that the first bluestones were raised between 2400 BCE and 2200 BCE.

All of that is fairly set in stone, so to speak, but this new research doubts Thomas' theory of the bluestones' geographic origin and how it ended up in southern England.

The new study argues that much of the evidence Thomas relied on was erroneous and limited, meaning his conclusions were off the mark. Instead of the rocks originating in Mynydd Preseli in south Wales, like he concluded, the new study further affirms other current research that says the bluestones came from Craig-Rhos-y-felin and Carn Goedog.

“New analytical techniques, alongside transmitted and reflected light microscopy, have recently prompted renewed scrutiny of Thomas’ work,” the study authors write.

“While respectable for its time, the results of these new analyses, combined with a thorough checking of the archived samples consulted by Thomas, reveal that key locations long believed to be sources for the Stonehenge bluestones can be discounted in favor of newly identified locations at Craig-Rhos-y-felin and Carn Goedog.”

As for the mechanism of how the stones ended up over 160 kilometers (100 miles) away from their quarry, that question will continue to keep archeologists up at night. A few researchers have suggested that they might have been transported to Salisbury Plain by the movement of glaciers, but most archaeologists argue that they were transported by an active human, most likely using numerous inland water networks and hauled over land.

“This work also highlights how easy it is to accept published findings as ‘gospel’ and not to offer a challenge.”

“This was the case with Thomas’s paper for over 80 years and yet our findings are fundamental to identifying sites where archaeological excavations might have the chance of finding evidence for the extraction of Stonehenge bluestones, if indeed they were extracted and transported by human agency rather than by ice.”