A blogging Carnival; Grand Challenges for Archaeology; reverse engineering Stonehenge

#blogarch

In response to the latest blog Carnival organised by Doug Rocks-Macqueen, the champion of archaeological blogging, over at Doug’sArchaeology, I am posting about the challenges of modelling a prehistoric roof structure in 3D.

The story so far…

My work is based on the idea that archaeological buildings are mathematical structures which can be detected and understood using the same principles that underpin the engineering of the built environment.

As regular readers will know, I have had the misfortune to have discovered how, in theory, the large Neolithic / EBA structures represented by postholes known as Class Ei buildings [1] worked, at least in plan and section.   The next stage is to model the structure in 3D to understand its assembly; the initial challenge is finding an appropriate starting point, since the value of everything else, and many man hours is dependent on this decision.  What is also challenging, at least in an abstract sense, is that the Ei building I am currently modelling at moment is Stonehenge, the well-known ritual monument and mystery at heart of British faith-based archaeology.

Where is the woodshed?

Much of the material culture of past was fabricated from timber, and, just as significantly, fuelled by wood, a material that is usually invisible to archaeology.  Thus, provision for fuel storage, like sanitation and water supply, is one of the basics that have to be considered in the analysis of built environments.
Traditionally, firewood is measured by stacked volume; a “cord” being a stack of 8x4x4 feet, or 128 cubic feet, including the spaces between logs.[1]  The calorific value of a cord will depend mostly on the actual mass of solid wood and its density, so it is difficult to be precise or make comparisons, but we could nominally say a cord was equivalent to 3,341 kwh [2].
A medium sized house in the UK uses on average 13,500kWh of gas for heat and cooking [& 3,200kWh of electricity] [3], so to replace this with wood require about 4 cords [16’ x 8’ x 4’]; so a year’s supply would fill the garage, or perhaps the spare bedroom.

Roundhouse Psychosis

In the previous post I explained why the large Wessex style “roundhouse” as illustrated and rebuilt is a fiction which is not supported by the evidence.  To be fair to all concerned, it never was a “peer reviewed” idea, but like the artists reconstruction that decorate the front of some archaeological texts, it has a far greater impact on our collective perception of the past than any sterile rendition of the evidence. 

The problem is that Roundhouses are more than just infotainment, a bit of harmless hokum for Joe Public, they are taken seriously, not only by those who commission and build them, but also by academics, and even fellow archaeologists who are obliged to shape their reports around this simplistic construct.  While dumbing down the academic system lightens everybody’s load, it is not good for the long term mental health of the profession, who have responsibility with ‘doing’ the day to day archaeology.  We like to think what we do is meaningful, making a contribution, and that we are collectively getting somewhere, it is about the only reward you will get.

As a field archaeologist, writing up sites, I had realised that the simplistic roundhouse only made sense if ignored a lot of the actual evidence from these structures, and, the majority of the structural features from elsewhere on the site.  Furthermore, those aspects of the evidence that reflected the archaeology of other published sites [roundhouses] were deemed particularly significant, reinforcing the cycle of belief.  Thus, apart from square four post granaries, circles are generally the only acceptable shape for a prehistoric buildings; both excavation and post-excavation were approached with same expectation, and to some extent purpose, of finding roundhouses.

Forthcoming 2014 Digital Exploration Season; Modelling Stonehenge and Edwin Harness.

Blogging your own research does allow you to preview what is coming up in future posts, and demonstrate despite the long gaps between posts you are still alive and kicking. [1]
My main in 2014 focus will be presenting 3D CAD models of Prehistoric roofed structures using Sketchup.

When I started building CAD Models of archaeological structures in 1990, it would have been quicker to build them in balsawood, and I little dreamt that one day a tool like Sketchup would not only run on a standard desktop, but also be available for free.
At present I am working on several [competing] fronts, with active models of Stonehenge, and an interesting Native American Building at the Edwin Harness Mound. In addition, I hope to do some additional work on Roman Military engineering structures, as well as Neolithic Longhouses should the opportunity arise. The problem that there is so much I have still to publish; among the built environments I have looked at in detail is a Romano British pottery at Orsett and Bronze Age fort which has a huge forge with a smoke bay.  However, as my work on Natïve American architecture demonstrates, you never what opportunities for collaboration may arise.
In this post I want to focus mainly on practical methodologies in 3D modelling of timber structures from archaeological ground plans.

Starting to model Woodhenge in Google SketchUp

The Story so far
Since I decided to blog this research five years ago, one recurrent theme has been my attempts to understand the largest class of prehistoric buildings Class Ei. [1] This includes Durrington Walls, the Sanctuary, Mount Pleasant, Stonehenge, and Woodhenge, the latter being the most interesting as a result of its non-circular plan.
When, as a result of Tim Darvill’s 1996 paper, [1], I first considered Class Ei buildings, I was initially very sceptical of their scale; I had been working on IA roundhouses where there were clear engineering limits, and these appeared to break my rules for timber structures.   
Against this, I began the compilation of a list of characteristics that indicated they were buildings. While the technical insight that resolved this dilemma probably came from studying the engineering of earlier Longhouses, ultimately, progress comes from breaking down your preconceptions by building models that don’t work. I took the unusual step of actually publishing some the models that had not worked in order to demonstrate why it was necessary to create a more complex solution.
It is harder than you might imagine to deduce from the evidence, rather than simply impose ideas on it.

'...when you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.'
Sherlock Holmes –
The Blanched Soldier, The Case-Book of Sherlock Holmes, Arthur Conan Doyle, 1927

Twelve reasons why Stonehenge was a building

Stonehenge was a building.  That’s it, no mystery. If it was a rectangle this would not be an issue, but British Prehistoric buildings are predominantly circular from this period onward. 
The rings of postholes at Stonehenge [Y, Z, Q, and R holes] are often ignored, or are thought to be redundant stone holes, but it is just one of a group of concentric timber structures known from various periods in British Prehistory.  Like Woodhenge, Durrington Walls, Mount Pleasant, and The Sanctuary, Stonehenge was a large timber building.  This was tentatively recognised by Tim Darvil in 1996, who called them Class Ei structures.[1]  

Stonehenge and the archaeology of the prehistoric roof

Postholes: cult or craft?

Most of the prehistoric archaeological sites of Britain, even Stonehenge, are covered with postholes, and it is my central contention that these posts were primarily the foundations of timber buildings. Further, since building is a rational process, postholes can be understood in terms of how posts were joined together to create roofed space.

Unfortunately, many academics have convinced themselves that some postholes are the product of a mysterious cult, whose rituals involved placing posts in the ground.

Despite considerable and ongoing research in this cult of postholes and their cosmology, the reasons for this strange behaviour are still not entirely clear. However, unlike the anthropomorphic polytheist religions evident elsewhere in Europe, adherents of these rituals, with remarkable prescience, seemed mainly to be acting out key themes from modern anthropology.

The archaeology of perception

This is my favourite cartoon; it is by the late Bernard Kliban, a New York cartoonist, and one of the founding fathers of the modern cartoon, and in my opinion, a genius of his art. Sometimes the world becomes so strange and distorted, that it takes cartoon to get it into perspective.

Debunking the myth of timber circles

The Myth

In archaeology there is the evidence, and there are the opinions put forward to explain and connect it.

In the highly subjective world of archaeological opinion, it has become widely accepted that the concentric rings of prehistoric postholes, once thought possibly to be buildings, were the freestanding timber equivalents of Neolithic stone circles.

These ‘timber circles’ have become central to modern understanding of ancient landscapes, as realised by Time Team. [1] Recently, Professor Vince Gaffney has even detected a ‘Timber Stonehenge’ [2].

They account for some important archaeological sites including Woodhenge, Durrington Walls, and The Sanctuary, and are even found in the Iron Age.

In 1996, Tim Darvill called these structures Type Ei buildings, [3][above left]. However, once others, particularly Alex Gibson, ventured the opinion they were too large to be roofed, they became ‘Timber Circles’ [4]. Many academics have long since moved off to explore this strange freestanding ‘ritual’ landscape, although, officially, it appears that the jury is still out:

“A timber circle is the foundation of a large wooden structure comprising a series of two or more roughly concentric rings of postholes which once supported substantial timber uprights variously interpreted as stanchions of a roofed building or freestanding posts. Timber circles are generally over 20m in diameter and the individual postholes are typically over 0.5m across.”

English Heritage web site. [5]

Actually, they are not too big, but entirely consistent with the scale other large oak timber roofs, and this can be demonstrated because they were made from trees.

39. Interlace Theory; Understanding Woodhenge

In this article I am going to start prising the lid off a box of treasures so extraordinary that it should change your vision of prehistory. The tool I am going to use is Interlace Theory. Due to the large number of drawings and illustrations involved, this article will deal with Interlace Theory and the next will deal with the detailed modelling of Woodhenge as a building.

Interlace Theory explains how large prehistoric buildings like Woodhenge were constructed, and is based on the detailed structural analysis of archaeological plans. It can account for the precise position, function, and three-dimensional relationships of each of the 156 postholes at Woodhenge, with a reasonable degree of accuracy. It resolves the series of problems with simplistic modelling discussed in the first part of this analysis of Woodhenge.

38. Bronze Age Architecture: Woodhenge

In recent articles we have looked at the typical architecture of the Early Neolithic in Northern Europe. This was clearly domestic and agricultural in nature. However, by the Early Bronze Age in Southern Britain, we see the development of much larger and more elaborate buildings. These structures are marked by concentric rings of posts and have been referred to as type Ei buildings.[1] Woodhenge, overlooking the River Avon, two km from Stonehenge, is one of the best fully excavated examples.

I chose Woodhenge because it goes straight to the heart of the matter: We have a complete plan, so there will be no ambiguity.

Angst, archaeology, and academics

Apologies for the recent break in transmission, but, as this article will hopefully explain, working in isolation for a long period on one topic can take its toll on your well-being. The previous articles form something of a sequence, and we have reached an important juncture, and the cause of much of my stress. But the time has now come to clear the decks of the emotional debris of a difficult journey, re-batten the hatches, get up to ramming speed, and set the controls for the heart of one the most central issues in British Prehistory.

In short, why Woodhenge, and similar structures, were buildings and how they worked.

The idea that previous generations grew trees and placed them in the ground to create a built environment does not, on the face of it, sound like a controversial proposition.

31. Primitive Rituals

I hope you read article no. 30. That’s where I let slip that ‘timber circles’ were buildings, some roundhouses were multi-storey, and Hadrian had a timber wall for while -- so you know I’m not here for the beer. But I wish we both down the pub; we could have a chat about all this, a dialogue where we could respond to each other. It would be good: I like you a lot already; you have had the good sense, taste, and intellectual interest to invest your hard won browsing time in reading this blog.

Speaking of beer, back in some golden summer of British archaeology, before the invention of health and safety, when the only unit of alcohol of note was a pint, muddy people would sit in pubs and have conversations about what they had just dug up, and what it all meant. If it was not obvious, at some point someone would say “it must be ritual then,” and we would all laugh, and then someone would be sent for to the bar for some more inspiration.

30. Not going with the flow

I studied philosophy, so I know you are reading this, or at least you think you are, but I don’t know why, or whether you have done it before, and if so, how often. If you have read none of the proceeding 42,000 words, what I am about to discuss may seem a little unexpected, but I am trying not to repeat myself, and besides, those who have bravely trudged through it all deserve some reward, so I am going to give a brief glimpse of what's coming up in the next 30 posts, because from now on it’s going to get ‘interesting’. In terms of ‘why I blog’, this is my belated contribution to an interesting Internet discussion.[1] It also reflects my concerns about how I blog.
So, before we go any further, it's important we have a heart to heart about what’s going on here. We are meeting in rather unusual circumstances; my concern is what is going on in your mind when you read this, and you may be beginning to wonder about what’s going on in mine.

19. The proper study of mankind is postholes

With all due apologies to Alexander Pope [1], and John Collis [2], postholes are quite important, but it is what they represent, the prehistoric built environment, that gives them their significance to archaeology.

An excavated posthole

The central importance of the built environment to archaeology, to its original inhabitants, and to builders was explored in a series of earlier articles, as was the basic problem of archaeological sites with lots of postholes that, once any roundhouses have been extracted, remain uninterpreted.