Genesis of a new theory for Neolithic Silbury Hill – a gradual merging of multiple, soul-releasing compost heaps.




Fig 1 Silbury Hill, approach from car park.

Silbury Hill, Wiltshire, England  (“the largest man-made mound in Europe”), approx 4,500 years old, as seen from the visitors’ car park (notice the open-air display board with information on the early stages of construction, as revealed by archaeological investigations).

Hello. Sorry to have been gone so long (nigh on 4 years!). My “Shroud of Turin” project took longer than expected – well over 300 postings on  sciencebuzz and my specialist site, to say nothing of 2000+ comments  I’m told on Dan Porter’s now-retired shroudstory site (this blogger even getting an appreciative nod in Porter’s final two postings).

Yup, I’ve drawn a line under the ‘now- not-quite-so-enigmatic’  Shroud.  Here’s a link to my final conclusions, which need not concern us here.

Back then to Stonehenge and Silbury Hill, especially the latter, where my latest thinking can be seen on the splendid ancient-origins website.

Yup, I discovered the site a mere 6 weeks or so ago through googling that Shroud (sorry to mention it again) and responded to a comment with some new research. Acting Editor Liz Leafloor (standing in for April Holloway, presently on maternity leave) placed an appreciative note in the Comments. I then spotted a fairly recent feature on the site posted December last year on artificial “burial” mounds, Silbury Hill included, which while acknowledging that no burial had ever been discovered in Silbury, despite numerous investigatory shafts and tunnels, seemed to assume that had been its initial function, hinting that something might finally turn up.   Xxxx  said the same back in xxxx, suggesting that there was a burial chamber that had been missed through being situated off-centre. (will track down refs in next day or two).

Well, all the old thinking came flooding back from my brief internet presence here in 2012, preceded by some kite-flying on my sciencebuzz site.

To recap: this blogger does consider Silbury Hill to have been a burial site, but one with a difference.  It wasn’t a place for interring whole bodies – or if it was, the burial was a temporary one, intended to reduce a corpse to a skeleton via natural decay processes, then retrieving the skeleton and/or bones for storage elsewhere. That kind of purposeful “defleshing” has been described elsewhere in the Neolithic archaeology literature, as an example of “excarnation”, which if deploying natural agents in the soil (bacteria, fungi, earthworms), or larger wildlife (e.g. feathered carrion feeders in ‘sky burial’  aka ‘towers of silence’ ) is further qualified as “passive excarnation”. That’s to distinguish it from “active excarnation” which is the brutally no-nonsense speeding up by means of sharp implements to deflesh the skeleton. Yes, it’s starting to get grisly again, and is no doubt the explanation for why the ideas expressed here 4 years ago not only failed to gain traction, but, if the truth be told,  no interest or attention either. Read: no feedback! So why has the ancient-origins acquaintance made me decide on a second attempt to address this difficult area, which admittedly risks ‘de-romanticizing’ Silbury Hill for some folk, if seen primarily as an aid to excarnation whether passive or active?

Answer: these few words that introduced the Dec 2015 article:

“  The people from the Stone Age also venerated their ancestors, so they had to make sure that their dead were at peace. If they looked after the spirits of the dead, then they believed that the dead would look after the living. The spirit had to be released so that it would not remain trapped inside of the body and it was believed that the spirit could leave the body only once all flesh had disappeared from the bones. At times, when the dead were not pleased with their funeral rites, it was believed that they could return to haunt the living.

Thus Prehistoric people built burial mounds made of earth or stones. They were designed as homes for the deceased and somewhat resembled the prehistoric dwellings of the living.”

Yup, it’s all in the presentation, isn’t it? Shift the focus from the mortal remains and the unspeakable methods by which they were degraded or stripped from the skeleton. Focus instead on the immortal soul, needing to be freed from those pesky mortal remains, and hey presto one has become an archaeological spin doctor!

The next step was to approach ancient-origins, asking it the site might be interested in a summary of ideas that were 4 years old, and to be re-presented in a more soul-oriented manner. The response was encouraging and I quickly penned a 1000 words or so. But two things were lacking: 1. Photographs that were my own, rather than grabbed from internet photoarchives with potential copyright issues, and 2.  Solid science, as distinct from long-shot speculation.

The first was easily addressed. I and the wife paid a visit to Silbury Hill, an easy two- hour drive,  together with the  surrounding  jam-packed Neolithic monuments (West Kennet Long Barrow, Avebury Stone Circle and the less well known Marlborough Mound on private property – Marlborough College!). The camera was clicking away the entire time, and the English Heritage trust thoughtfully provided an open-air display board with some of the very same artwork (probably copyright) that had so appealed to me in the Leary/Field book.

composite 3 pix from silbury display board

We have Judith Dobie to thank for these splendid ‘artist’s impressions’ of the initial stages of Silbury Hill construction, based on numerous archaeological investigations, starting in 1776. One can see them in Leary and Field’s book “The Srory of Silbury Hill” (2010, English Heritage) and, as indicated, on the display board at the visitor’s car park on the A4 road adjacent to the Hill (from which these pictures were taken and then arranged in a single line).

Now this is where it starts to get interesting,or at any rate, heads off in an entirely new direction that one will not find elsewhere in the literature, bar a few asides that will be listed later.

There’s a wealth of detail in the Leary/Field book regarding the complex manner in which Silbury Hill took shape, based on the finding of their own and earlier tunnelling investigations.  Those details cry out for explanation, but none is to be found in that otherwise splendid book. The L&F postion is summed up in this headling in the Mail: “It was all an accident”.

Silbury Hll Mound Solved – It was All an Accident

This blogger will be addressing those peculiar details of Silbury’s construction, described by the celebrated Atkinson as resembling a “layer cake” etc. But there was an enigmatic feature of the proto-Silbury, long before any complex layers were added. It’s what Leary refers to as the initial “organic mound”. That’s when science and art co-synergized, with those splendid and haunting reconstructions in the L&F  book  (see above) of the first stages of Silbury construction. One has to look hard in the book to find who produced the artwork: it’s one Judith Dobie, mentioned briefly on the rear fly leaf.

(Yes, the same three ink washes as on the display board appear in L&F’s book).

It’s that term “organic” that intrigues this blogger. It is not defined in the book. Indeed, it slips in almost via the back door so to speak, and it took a patient trawl through many pages to form a view as to what was meant or implied by “organic”. (Maybe any carbon-based material of plant or animal origin, regardless of degree of preservation?). The incentive for doing so should be clear, given this blogger’s view that Silbury was a home for at least some part or portion of the mortal remains of deceased Neolithic pastoralists settled on the wide open spaces of the Wiltshire chalk uplands.

OK, here’s the result of my homework, listing each and every manner in which Leary deployed the term “organic”.

It makes its first appearance on page 39, where, referring to the centre of the primary mound (gravel plus  replaced top soil) we read:

 “Merewether also noted that there  were ‘great quantities of moss still in a state of comparative freshness (ref No.37) and that it still retained its colour. He believed that this material, together with teh freshwater shells, had come from a moist location and thought it must have been derived from the west, north or east sides of the Hill where the Beckhampton Brook flowed past the foot of the mound. Sealing the turf stack was a desne layer of organic material containing fragments of small branches and emitting a peculiar smell. In addition fragments of what he thought were plaited grass or string were discovered in this organic deposit. This was not recorded in any of the later (ed. post 1849) excavations and is likely to have been fungal mycelium, probably introduced in 1776 (ed. first probe of mound interior via vertical shaft).


“Organic ” next appears on Page 62

Referring to the small central mound of gravel, covered by a mound of turf and topsoil, with description attributed to the celebrated Richard Atkinson in his 1968 tunneling:

“…four complex layers of contrasting black marshy soil, white chalk and coloured flint gravel with an overall diameter of some 34m and reaching an estimated depth of just over 5m…

”On removing a portion of turf they were astonished to see that it was still green…

“Not only plants but insect remains survived …  “flying ants” …”ants were lying dead in the turves long before becoming incorporated into the mound.”

:”over this organic phase was a large mound of chalk…”

Presumably “organic” refers to both relatively well-preserved recognizable planr and animal matter AND to dark coloured muds etc of less certain composition.

Oh heck, this can wait till later. Let’s cut straight to the chase. The proto-Silbury can indeed be described as an “organic mound”, but one of very peculiar and, at first sight, bizarre construction. Indeed, its construction needs to be known to anyone wishing to get to grips with the enigma that is (or was???) Silbury Hill. To that end I cobbled together these two diagrams using MS Paint to summarise whay Leary and Field expressed in words, and Judith Dolby with he pen and brush.


Fig 6 My schematic diagram of first 3 stages in life of Silbury Hill

LEFT: initial site with top soil and turf overlaying clay/flint subsoil and bedrock chalk. CENTRE: top soil removed to expose subsoil. RIGHT: heap of gravel placed on subsoil (to deter downward earthworm migration?) 

Fig 7 My schematic diagram of next 3 stages ,

LEFT: the top soil  and turf has been placed back on top of the gravel, maybe more ordered than shown. CENTRE: additonal layers of soil, subsoil have  etc have been added, together with a mysterious dark material (wormcasts?). RIGHT: excavations have been made (3 are shown beneath the red ? marks) and then back-filled with the same excavated material. Was something being ritually interred with that back-fill? Mortal remains of recently deceased?


So what ate the unusual indeed unexpected features you may ask?

There are three:

  1. What’s described as the tallest man-made mound in Europe, predominantly chalk construction, began as a mound of GRAVEL (you know, that stuff that easily slips and settles on itself if you try to make too tall a pile). WHY GRAVEL?
  2. The gravel was not simply placed onto unprepared ground. No, the topsoil was removed down to subsoil first, to a base that is described as clay-with-flints, which one is tempted to describe as “non-organic” 9hardly the most logical start for an “organic mound” one migh tthink.
  3. It gets worse. The second addition, placed on top of the (shifting?) gravel heap is described as having plant matter, some amazingly well-preserved after 4,500 years, even still green. It’s considered highly likely that it’s merely the removed topsoil being ADDED BACK ON TOP OF THE GRAVEL, super-topsoil one might say, or at any rate, elevated topsoil.

No why on earth would anyone go to that trouble, especially if the initial aim had been to construct the highest artificial hill in Europe?

Answer? Maybe that was not the aim,  as considered also by L&F: mMaybe that proto-Silbury Hill, that so-called organic mound, served an entirely different purpose, one that was not merely ornamental. Now what could that be?

To those who are gardeners, the answer is obvious. If one makes a heap with turves on top, especially inverted turves (admittedly an exercise of imagination, since we’re not told if that were the case) then one has the beginnings of a compost heap. Why? Because composting to make an organic mulch for one’s roses etc benefits from having well-aerated conditions that encourage the right type of bacteria and fungi to grow, ones   break down dead plant matter to …  compost, the latter contributing to soil HUMUS, which helps plants establish through encouraging healthy growth of roots.

That was the cue for another small exercise of imagination. What does one invariably find when turning a compost heap with a folk, as one’s recommended to do at intervals to improve aeration? Answer: earthworms. They may be large or small, depending on species, but they are attracted by the dead decaying plant matter. It is said that it’s not the plant debris itself that is the attraction, but the microorganisms that grow on it – bacteria and fungi. That’s a detail that need not concern us for now.

The important thing is the realization that Leary’s “organic mound” looks for all the world like the initial phase of a compost heap, and a well aerated one at that being elevated, free-draining etc.

But there’s a problem. While the gravel base keeps it well aerated and well-drained (excess water being the enemy of compost heap, encouraging anaerobic conditions and the wrong kind of bacteria) it would be a barrier to those helpful earthworms. One would be dependent on the replaced top soil having earthworms to get the heap off to a good start. One would be well advised to add earthworms deliberately, just to be on the safe side.

Might they not escape from the heap, if finding conditions not to their liking (like finding non-ideal food?).

Stand by for another exercise of imagination: the gravel and underlying subsoil were a deliberate ploy to keep added earthworms CAPTIVE in the elevated compost heap.

Why would one need to keep them captive? Why might they want to migrate back to ground level and try their chances elsewhere?

So far I’ve said nothing about the diet of those starter worms, though it might be assumed they would not starve if the turves were inverted, allowing the latter gradually to rot down, creating  a slow but steady supply of ‘worm food’.

Just a single compost heap, fed with goodness knows what, but clearly not kitchen scraps? No. Look at the next phase of Silbury construction, where we see the initial heap encircled by what might be called satellite heaps. No, not just one compost heap, but many, all roughly the same size, except maybe the starter being the biggest. Silbury as a communal composting centre, designed for recycling (organic material “X”  still to be clearly specified,  origin uncertain -> compost)?

But wait: the modern day compost heap does not multiply, nor does it grow like topsy, ever wider, ever higher. Why not? Answer, because the end-product, with a wholesome if earthy aroma if conditions were right, is harvested at intervals, and taken for use elsewhere. That clearly did not happen in the case of proto-Silbury, which progressed to primary Silbury, secondary Silbury, tertiary Silbury etc.

So what was being fed to those worms, whether adventitious or (more probably) deliberately introduced, such that there was NO DESIRE to harvest the end-result, that the end-result stayed exactly where it was, being progressively overlaid with more soil, more worms, more ‘offerings’ and finally capped off with vast amounts of chalk, excavated from the nearby encircling ditch.

Ah yes, that ditch.A few words are necessary regarding the ditch.

Now suppose you dear reader had been intending to construct a large artificial mound for whatever reason, purpose unspecified, and had decided to use the local chalk.

Would you (a) decide on the likely size of you final hill, and  only excavate chalk outside of the chosen ‘footprint’ area?

Or would you: (b) decide that it was too tedious to carry chalk from periphery when the initial heap was still small and proceed to dig out the nearest chalk at hand, creating a circular ditch that then ahs to be back-filled  chalk that was from further afield.

Which involves the greater work? Digging chalk and carrying it a few metres or tens of metres to where it’s needed, creating a single ditchOR digging, back-filling, digging, backfilling?

The answer is obvious, and as Leary and Field themselves point out, there was clearly no intention at the start to create something the size of Silbury as we know it. The initial intentions were more modest, and one clearly must look to the detail, so admirably expressed in those line drawing s, with those MULTIPLE MOUNDS to deduce the initial raison d’être.

What could have been serially added to that proto-mound, with nothing being taken away, such that over years, probably decades, probably generations (3 or more?) Silbury Hill gradually took shape as a landscape feature, without that having been the initial intention?

There seems one, and only one logical explanation for all this repetitive activity that takes the form of small heaps that gradually coalesce to become one, each with mysterious “organic” character with those allusions to “dark soils”, “muds” and even earthworms.

Silbury was the place where one took the mortal remains (possibly a very small part thereof) to be communally interred under soil, with an implantation of earthworms.  The inclusion of those earthworms was probably dictated in the Neolithic mind more  by vague ideas re natural recycling of ‘stuff of life’, albeit imperfectly given that animal matter is said not to be an earthworm’s preferred diet   (preferrign we’re told plant rather than non-plant material).

In short, Silbury was a communal compost heap, but one to which there were additions only, not subtractions. The additions were probably modest in size, probably nominal and symbolic, e.g. notably the HEART  of the deceased only(?) The return of that individual’s key organ of life, the heart, may have been viewed as sufficient to liberate the soul, the immortal spirit of the deceased. Leaving nothing offensive in its place, and well-protected, well-concealed  anyway in the early stages of what today we would call biodegradation. As and when signs of that process began to appear on the surface (worm casts, or indeed the worms themselves after rain) there was a simple remedy – place more gleaming white chalk on top. Conceal the evidence of what was going on, out of sight, out of mind.

Incidentally: there one question that needs addressing later: why was chalk added if the intent ion was merely to create compost heaps? Might a need have been seen for chalk to mask the unsightly-looking heaps ,  making the ditch a mere by-product  OR was a ditch around the interment area deemed essential, for reasons that can be discussed later?

The fact of there being a ditch AND a bank of the same excavated material on the inner (mound) side, acting a raised screen or rampart –  see above-  must surely point to the second reason.

Let’s stop here for now. Take away message?  Silbury Hill was intended initially as a communal necropolis for receiving and honoring the mortal remains of the newly deceased, where they were interred with soil and earthworms, a ritual that was intended to free the soul, while returning what was left to the soil.  How much of the deceased was interred? It could have been as little as the heart – given its association with life when visibly beating, Or it could have been more, possibly the entire body if the skeleton were later retrieved. My feeling, based on little more than intuition, is that it was just the heart with at most a few other readily harvested vital organs. The fate of the rest of the body can be addressed another time.

Next posting:  The focus will be on the embedded sarsen stones of Silbury Hill (“like raisins in a cake”). What function did they serve?

I say they can be readily accommodated within the new interment theory.Let’s see if there’s any response to this and my ancient-origins posting first, and whether it’s positive or negative!

Postscript (added Tuesday April 12) : I guess my difficulty with the expression “organic mound” is as follows: first, it seems unlikely that organic matter makes the major contribution. Inorganic matter in the form of the gravel, the various additions on top of the replaced topsoil etc would make inorganic matter the major constituent. Then there’s the difficulty in discerning which organic material is being seen as the major defining constituent of the (minor) organic part of the organic mound. Is it the turf, mosses etc associated with the replaced topsoil?  Surely not, given their amazing state of preservation which while defying common sense perceptions re biodegradation, appear at the same time to detract from their playing any functional role that would justify a focus on “organic”. Or is it the mysterious dark layer above the replaced topsoil when we are told so little about its nature or source, whether as being of marshy origin, or some kind of mud, or imported dark soil. Or is it the ants, snails and other assorted fauna, the presence of which in buried topsoil is hardly surprising? Or is it something to do with those mysterious scooped out parts (see the three question marks on my diagram above) where the same excavated material is returned? Or maybe the imported additions of  out-of-area “home soils” with a range of distinctive flora that are referred to briefly as perhaps signalling the “real” purpose of Silbury Hill,  a celebration of habitat diversity,  (about which I’ve said nothing as yet, through still being unable to decide if they are or are not the defining feature of the “organic” mound).

Would this blogger/retired science bod have deployed that term “organic mound” for so varied an assortment of biological contributions to the proto-Silbury mound? The frank answer is no, since it leaves the recipient of one’s terminology puzzled as to what importance to attach to the term. I might have called it the “oddly-constructed embryonic Silbury” and flagged up the uncertainties regarding some of its layers and/or other contributions, notably those with dark material, which may or may not have been imported soils.

I think I might have been content to call it the “peculiar primer-mound”. That then prepares the reader for the undeniable fact that almost everything about Silbury Hill could be said to be peculiar.

Hopefully, my proposal that the earlier stages of Silbury served as a communal site for composting human remains, ones that leave no trace after millenia of earthworm activity, will serve to reduce some of the perceived “peculiarity”.  But I don’t undersestimate the difficulty of getting my readers to buy into the idea that Neolithic farmers took a very different view to those of modern internet readers as to how best to dispose respectfully but efficiently of the mortal remains of their loved ones. Let’s not lose sight of two practicalities: consigning to a non-shallow grave, out of easy reach of animal scavengers, was a tough option, when the bed rock was chalk, and one had nothing but deer antlers with which to excavate. Cremation on an open pyre? That might have been seen as a terrible waste of dried timber on increasingly deforested upland, especially in winter time, when trying to stay warm was a priority.




About Colin Berry

Retired science bod, previous research interests: phototherapy of neonatal jaundice, membrane influences on microsomal UDP-glucuronyltransferase, defective bilirubin and xenobiotic conjugation and hepatic excretion, dietary fibre and resistant starch.
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