Thursday, May 17, 2012

A new theory for Silbury Hill - a communal reliquary for the "souls" (and vital organs) of the recently-departed?

 Silbury Hill, Wiltshire, England (approx 1 mile from Avebury Stone Circle and 25 miles from Stonehenge). Communal organ reliquary?

From the Daily Telegraph, 2007"The original purpose and use of the hill, which is south of the village of Avebury, is still a mystery. Theories suggest it was either a burial mound, a solar observatory or a representation of a Neolithic goddess. "It is very unlikely we will ever know why it was built," said Robert Bewley, English Heritage regional director for the South West."

Well, almost 5 years on from that article and its pessimistic soundbite, I’ve been reading a highly factual account of man-made Silbury Hill in Wiltshire, published in 2010.

The Story of Silbury Hill by Jim Leary and David Field (foreword by David Attenborough), English Heritage

 It gives a commendably detailed account of the numerous excavations that have been made – right to the very centre, tracking close to ground level to penetrate the original core. 

  The aim was to find what this enigmatic hill was for, what (if anything) it concealed, and why anyone would go to so much trouble. 

Well, I hope the authors will not mind if I provide a trailer, so to speak, of what lies between the covers of their fascinating book, and quote bits from some key passages (no pun intended).

  What those miners and archaeologists did NOT find was what, for now,  I shall refer to as "X", which I believe was buried at Silbury a little at a time, plus a few baskets-full of soil or chalk to hide the evidence, then more X, then more soil and chalk. Why not? Because X is biodegradable, highly so, and which millennia later would leave scarcely any evidence, if at all, of its existence.

Artist's impression - but based on the excavation evidence

 Silbury Hill began as Silbury Mound, which we learn  was simply  as a heap of “sticky” (hmmm) gravel. Yup, that’s what they found at Ground Zero, sticky gravel.  Bit by bit the cone enlarged to make what a few generations later was the highest man-made mound in Europe, as it remains to this day.

So what was X?

I trust the authors do not mind if I turn this into a tease for the reader by quoting some carefully selected  passages from their book, highlighting certain words and key phrases. I will then state simply what I consider was X, leaving readers to recoil, cringe, feel nauseated whatever, and then proceed to write a follow-up post to this missive, which goes on to suggest the real purpose of one of Silbury’ two sister structures - Stonehenge, leaving Avebury for later.

Yup, despite being some 25 miles apart, I believe the two are related – at least in a utilitarian sense -  even if not operating as a dual unit. Indeed, the idea for one may have evolved from the latter, or they developed as different solutions to the same problem of being a settled Neolithic homesteader. The problem?  Clue – it’s one of everyday life – and what inevitably follows... And curiously it’s centred on aesthetics – even if at first sight what I write here may seem to fly in the face of aesthetics.

Let’s now look at that book.

Page 96  under “The earliest mound”

“Deep inside the tunnel...  it was possible to make out, dull, golden, sticky gravel resting on top of the stripped surface. The gravel had clearly been piled up into a small rounded mound a little less than 1m high and nearly 10m in diameter; hardly a worthy predecessor to the giant mound we see today, but a mound nonetheless.”

Page 97 under “Pieces of Place”

(Around the gravel mound) ... a ring of stakes had been hammered into the ground to define the perimeter of a larger 16 metre area. Individual loads of mud and dark soils, probably carried in baskets or hides, had been tipped into this space to create a mound that was about waist high...”

Facing page: an artist’s reconstruction with an interesting caption: “The organic mound surrounded by stakes”.  (what do you suppose the authors meant by “organic”?).

Page 99:  A few metres away to the south and south-east, two smaller mounds were visibly outlined in the section, and others may well exist beyond the confines of the tunnel. Made from dark organic mud, these two small mounds stood less than half a metre high. They were not natural features but deliberately constructed mounds that were added to and modified over time, and one even had a tiny gully dug around it; like a small scale model of the final Silbury. This is an entirely new discovery, and we can now say that the early phases of Silbury do not comprise just one monument, but a number of them that later became subsumed into a single form.”

Further down:

“The soils from all these early mounds preserved organic material astonishingly well...   Insects are ...  staggeringly well preserved... There is an abundance of weevils and some leaf beetles too, as well as a variety of dung beetles, which feed on the droppings of animals such as cow and sheep...”

“seeds and plant remains confirm evidence from the insects that these early mounds were set in mature, well-grazed grassland...”

Page 102 “Mound building stops”

“...  pits were dug into the top and side of the central organic mound... These pits were not large – around 1 metre in diameter and depth... their fill seems to have been little more than the dug-out material pushed back in...”

Page 103   “... and then resumes...” (i.e. mound building)

“Mound assembly continues, and these pits, along with the organic mounds, became sealed under dumps of different materials that had been tipped over the top. This was made up from basket-loads of top soil, chiefly gathered from soil that directly overlay chalk, and therefore from beyond the immediate clay-with-flints well as basket-loads of chalk, clay, gravel and more turf..”

“...turning to (famed Silbury/Stonehenge archaeologist) Richard Atkinson’s evocative description  helps to conjure the image of a cross-section through these multi-coloured and interweaved layers : 

"Seen in section, these upper layers have a stripe pattern, like a polychrome tiger’s skin the white chalk contrasting sharply with the dark-grey soil and the yellows and browns of the gravel and clay. Together these layers formed a mound with an estimated diameter of 35m and which was perhaps as high as 5m or 6m...  a number of ... sarsen boulders were present as well ... deliberately incorporated within the body of the mound as an element of its composition ... like raisins in a cake...  The material for these early mounds had been carefully chosen; this was no random spoil heap, but pieces of other places carefully piled high."

Still on p 104 under “The white mound”

Once this intricate stack had been built up, chalk was then added... sometimes mixed with clay... which would have formed rings round the earlier monument...with the material engulfing the earlier organic mound and forming successively larger white mounds...

Atkinson ... described Silbury Hill as ‘an enormously complicated and highly-coloured layer cake’... and in The Listener the organic mound formed  ‘a kind of enormous biological club sandwich’.

Moving to p 106, and referring now to the encircling Silbury ditch 

“The unweathered sides of this ditch suggest that it had not been open to the elements for long before it was, very deliberately, backfilled and re-cut slightly further out. This happened not just once, but at least three times, moving successively outwards with each cycle of backfill and re-cut; the ditch, like ripples in in water,moving ever further out...  no sooner had one ditch been dug, than it had to be filled and cut slightly further out. Perhaps the bank and ditch enclosure needed to move further outwards to make room for the ever expanding chalk mound within it ... Silbury Hill was constantly being adjusted. There was no fixed plan.”

All this is a far cry from any notion that someone once gave the order – "build me the biggest hill ever". This was no ordinary hill. It was an organic thing, that word again, though whether organic in the present context (meaning to grow progressively) is what the authors mean by their term “organic” for the original mound, I am not sure. In fact, I  have scoured the earlier chapters of the book for that term organic, but while doing so another meaning for the term entered my head. 

I refer to the one used by gardeners and farmers for “organic” compost, i.e. dead and decaying plant and animal material that gradually rots down to leave nothing resembling the original material, at least  in a well aerated heap, except dark, crumbly, wholesome-smelling humus.

By now, dear reader, you should have an idea as to the direction in which my thoughts are going, especially when you see those bolded-up words for soil, dark soil, etc etc.

Thoughts of the imperatives for making a good compost heap were reinforced by the following references to crushed chalk and chalk boulder walls that were built within the mound as it progressed:

“The deposits on the top were made up of dumps of crushed chalk, laid one on top of another, and held in place by large loose pieces of chalk rubble...  the walls were carefully tilted inwards to hold the chalk in place, thus preventing collapse... The rubble walls hold the horizontal chalk layers in place, making it extremely stable. The voids left by the loose-fitting rubble allow rainwater to drain freely through the great mound, thereby limiting erosion. It is the reason the mound is still standing 4,500 years later.

Page 111:  The shape of Silbury

“... the mound is not in fact truly circular, but built in a series of straight lengths, and its outer shape may have been dictated by a series of radial spines, between which are straight construction lines forming something like a spider’s web ... it could have been dictated by a series of buttresses that help tie the structure together... the idea that Silbury Hill was (later) reconstructed as a garden mount... can be discounted. “

Page 112:

The radiocarbon dates taken from the Hill suggest that its overall construction was rapid, thrown up in the years between 2400 and 2300 BC, and therefore it perhaps took only three of four generations to go from small gravel mound to the massive final chalk mound. Work on it, therefore, must have been frenzied at times...”

Thanks Jim Leary, thanks David Field for that cogent and illuminating exposition. I wish I had your economy and precision with words.

So what is one to make of all that – a hill that began as a mound, around which was constructed radial revetments ('retaining walls'?) of chalk boulders holding back layer upon layer of soil, turf, crushed chalk - but what else (X??)

The only rational answer I can think of (while recognizing that things did not always happen in prehistoric times for rational reasons) is that something (X) was being deposited, covered over, then a new addition of that something etc etc – rather like building a compost heap, but with no intention of later harvesting (thus the chalk etc). What could that something  X have been. Could it have been “organic” but something that has rotted down so completely as to leave nothing except dark soil?

The centre of the 'organic' mound.  Why is the soil so dark , and in layers?

One thing is for sure. It could not have been human corpses, or at any rate intact corpses. That would have left skeletons or traces of bone. 

Could it have been just part of a deceased person (or less likely animal) which was the part our ancestors might have wished to dispose of quickly, allowing them to delay subsequent disposal of the rest of a cadaver. Was it a part that Neolithic man might have wished to dispose of quickly and systematically to avoid attracting wild animals – rats, flies ,foxes,  wolves etc - that would have picked up the scent from afar, and come to investigate, posing a threat to children, livestock, public health etc?

There is a part of the human anatomy that ticks these boxes, and though   
I hesitate to mention it, the internal organs - of the thoracic and abdominal cavities?

Is it possible that there was a passing fashion in Wiltshire, lasting approximately 100 years,such that when there was a death in the family, the first thing to be done was to convey the corpse to specialists at the Mound(initially) and later the Hill, where the internal organs would be removed for immediate interment with due ceremony and ritual.  They would have been quickly harvested, then covered over with soil and chalk, and the remaining cadaver, with better preserving characteristics,   then handed back to the grieving family for disposal at leisure (maybe taking what was left to nearby Avebury or even Stonehenge for second-stage ceremonial disposal)? 

Is it possible that thousands, nay tens of thousands of such additions were made to Silbury Hill in its relatively short life as a disposal site? Has the biodegradation of those organic remains left small cavities that have contributed to the sharp drainage that our two authors claim is the reason why the Hill has survived the downpours of four and a half millennia?

Addendum: . Francis Pryor estimates that by 4000 BC the population of Britain was around 100,000 while that of Ireland was some 40,000. For 2000 BC his estimates are 250,000 and 50,000 respectively. Reminder: Silbury Hill was constructed in a relatively short time span between 2400-2300BC, based on radiocarbon dating. That century coincided approximately with Stonehenge's "late stone phase", i.e. 2450BC according to the English Heritage visitor guide, but well before the "final stone phase" about 2000BC.

Probably most of those preferred to live on the chalk uplands, having given up a hunter-gatherer existence in the dense woodland that still covered most of southern England. That would mean an increasingly large number of mortalities per year in a relatively small area, creating  a disposal problem. How many more barrows can be added to the landscape, taking up valuable land for livestock and crops?

Oh, and I see that one of our authors - Jim Leary -  discovered a "sunken floor" in the foundations of the Marden Henge (of which only the bottom 15 cm remain), purpose unknown. Hmmm: was it the equivalent of a mortuary slab?

Finally: for a scientific hypothesis or theory to have value, it must have predictive utility. OK. I predict that the darker soil seams in that hill will be enriched in the chemical elements that are in human tissue. The soluble ones will probably have leached out, but given the alkaline conditions that pertain in chalk, I suspect there may be elevated levels of iron, deposited or precipitated as iron (III) oxide or hydroxides. Note the earlier comment/link re the 'iron pan' formation, which may simply be a consequence of local geology, or there again, maybe not.

It is also possible that there is still "fossil" carbon in the dark-coloured soil if the equivalent of plant humus. Radiocarbon-dating, matched against appropriate controls from non-dark clay and other debris could point to an exceptional contribution from a Neolithic carbon-rich source.

Could it be that ritualistic evisceration("cleansing") of the recently deceased was a de rigeur convention ("fashion statement") for a brief period (a century or thereabouts) in progressive Neolithic society? Or there again, a monument that contained the hearts of the deceased (and much else besides) may in time have come to be seen (from afar)as a powerful symbol of the continuity of life and society. Maybe the heart and soul were perceived as one for that brief period of history.

My theory for Silbury Hill: it served as a communal organ reliquary, or, more picturesquely, as a visceral Valhalla.

Next post - Stonehenge.  Complementary to Silbury - or a separate  facility also centred on novel and evolving means for disposing of the mortal remains of the deceased in response to the pressure of growing population density?

"Stupas originated as circular mounds encircled by large stones" (wiki)

Some might see parallels with the Buddhist stupa  also described as a giant outdoor reliquary...

 Colin Berry, aka sciencebod  May 17, 2012


Anwar Ali Malik said...

nice chemistry experiments

Robert John Langdon said...

Interesting Idea!

But you will find the 'organic' material is due to the fact it was built as an island and the materials found would be plants, such as reeds.

for details


sciencebod said...

Good morning Robert

As I expect you know, some of the plant remains at the centre of the hill are in an amazing state of preservation, as Leary and Field have described, with "grass and moss still visible" and still "green". But I think it highly improbable, don't you, that any admixed human soft organs would have been preserved or even mummified, given that the atmosphere would surely have been damp, allowing growth of bacteria and fungi, with no plant cell wall to contend with? The absence of obvious human soft tissue does not mean it was never there initially, but there may be sophisticated tests, e.g. for bacterial or fungal cell wall substances, that might suggest it was once there...

I'm now interested to know what chemical and/or biological analyses were performed, especially on the darker soil, and on that "sticky gravel". Some fatty acids are said to be highly resistant to biodegradation...

I've emailed Jim Leary, but got an out-of-office reply.