As Stonehenge was assailed by the spades of English Heritage-approved archaeologists last week, I was on a field trip with a group of anthropology students in the Preseli Hills in Pembrokeshire, building sweat lodges and exploring the local Neolithic sites. This fascinating area is the very source of the bluestones identified by Geoff Wainwright, former head of archaeology at English Heritage, and Tim Darvill, head of archaeology at Bournemouth University, as the key to their theory of Stonehenge as a centre of healing, or a "prehistoric Lourdes", as the BBC and most other media put it.
Undoubtedly, the question of why our ancestors 4,500 years ago transported these stones more than 150 miles to Stonehenge is a fascinating puzzle, but it is not clear precisely what the archaeologists are hoping to uncover from this unprecedented dig, apart from acres of news coverage. Religion is about magic and medicine, and all rituals are concerned with healing; furthermore, it is hard to see how the hypothesis that bluestones were considered particularly efficacious might be tested.
Looking around the Preselis at the spectacular bluestone crags of Carn Menyn and the surrounding stone circles and burial mounds, it is striking that many local stone circles, such as Gors Fawr, are not made of bluestones. And at Stonehenge itself, the theory provides no explanation for the initial replacement of the bluestone double circle by the enormous and distinctive sarsen stones we see today. Were those lintelled and towering sarsens added as a mere antechamber to the diminutive bluestone Lourdes? And if bluestones were thought to possess such power why didn't other nearby groups incorporate them into their equally unique architectures, such as Silbury Hill, one of the world's largest prehistoric structures, and other monuments at Avebury?
There is much evidence that the late Neolithic was a period of economic crisis, as the hunter-gatherer lifestyle collapsed and agriculture began. This is partly expressed through the increasing incidence of deficiency diseases, seen in the skeletons in burial mounds. Clearly, these impressive monuments and the tremendous material and cultural investment they represent are of major significance. For me, the cultural context of this period provides the most powerful explanation of the stones, and to understand what might have been going on we need to put ourselves in the minds of our ancestors and raise our enquiring gaze to the horizon and to the heavens.
Archaeoastronomers John North and Clive Ruggles have shown that ancient stone circles were ritual centres partly designed to link the Sun's solstices with the Moon's standstills. While this sounds rather esoteric, it gives rise to a simple, compelling and revolutionary theory. My research conducted over the past ten years has shown that the particular paired alignments chosen were always those that ensured a dark Moon would occur within the week when the solstice Sun seemed to rise or set on the same horizon point. The monuments are machines designed by shaman-priests to convince their cattle-herder people that an ancient but dwindling respect for the Moon could be displaced and combined with the movements of the Sun, so providing a religion more appropriate to the male ownership of moveable wealth. Most stone circles thus "solarise" ancient death and resurrection rituals through the curative power of the dark Moon, still practised by hunter-gatherer cultures today.
The "astro-archaeological" theory is a parsimonious explanation of the 19-bluestone horseshoe, since lunar standstills follow a 19-year cycle, and the dolerite bluestones with white feldspar inclusions are, when wet, suggestive of the starlit sky of a moonless night. As above, so below: sarsens and bluestones together may well have served to simulate an underworld journey through the longest night in the heart of winter - a time more likely to finish off the sick rather than heal them!
Interestingly, the Avebury monuments achieve the same astronomical effects and timings in a different way, with the white chalk of Silbury Hill, scraped clean of grass, operating as a facsimile of the crescent Moon before and after dark Moon. Exactly 40 years ago, archaeologists dug a passage into Silbury Hill, expecting to find buried treasure, royal bodies or at least a clue as to what a pyramid was doing in the Wiltshire countryside. They, like their successors at Stonehenge, might have been better off downing tools and looking to the heavens instead.
