File:Carn Menyn, the Stonehenge debate - geograph.org.uk - 1451298.jpg

English: Carn Menyn: the Stonehenge debate A geology excursion pauses to ponder the Great Debate that centres on this outcrop, for many years considered to be the source of the spotted bluestones of Stonehenge. A difference of opinion exists as to whether the bluestones arrived in Wiltshire by natural or artificial means. Archaeologists (and New Age romantics!) believe that suitable stones were selected and perhaps prepared here then transported by human agency via rivers and across the Severn to their final destination on the Salisbury Plain. Geologists (and perhaps those of a rational/pragmatic bent) support the theory that the stones were carried to Southern England on a glacial icesheet which deposited them in striking distance of the location chosen for the great monument.

While no one disputes that the construction of Stonehenge required massive human input, both sides in the debate wield convincing and fiercely argued evidence for and against each hypothesis.

A Millennium project to 'recreate' the human transportation of a bluestone ended when the stone sank in the Severn estuary: the case remains 'not proven'.