26 April, 2016

Reverse engineering the past

It is spring, the swallows have returned to the farm, so it is time for a mission statement, or an explanation what after 8 years on the internet Theoretical Structural Archaeology is all about, again. 
In essence it very simple, just as knowledge of potting is necessary for understanding pottery, so understanding engineering is important for a archaeologists dealing with the archaeological remains of engineered environments.  However, this really about being able to think like potter or an engineer, it concerns archaeology as a mind-set rather than a written subject.  Not that it is actually that technical, given the sorts of the data sets we recover, and of course it is only one of many core skills required for field archaeology.  The key point to grasp, at least in principle, is that engineered structures can be described mathematically, and therefore can be modelled.  
While I regard this as a universal principle, my particular interest is those prehistoric timber environments of Western Europe, often represented by postholes usually without stratigraphy on plough reduced sites. [Right; E.G. a 10m² of the multiperiod site at Orsett, Essex].
This is Process Archaeology or how to converting dirt to text; any understanding has to start with soil; while knowing how to pull it apart and record it is essential,  it is the process of converting soil to text that is the essence of archaeology; get this bit wrong and it can invalidate much of what subsequently uses this written information.  It is in this context that an understanding of some of the underlying principles of the built environments can prove invaluable if the objective is interpreting the archaeology.
However, there is clearly an issue with what constitutes “engineering” and how would you distinguish from any other feature.  

Motivational archaeology 
Broadly, in addition to cultivation, we can perhaps think of digging in terms of engineering and disposal; however, regarding burial as an example of the latter or mining as an example of the former is probably inappropriate, even in the interests of simplicity.
So let’s go with;
  • Engineering
  • Cultivation
  • Disposal
  • Burial
  • Mining / Quarrying
  • Other
“Other” is to cover the digging out a badger set for entertainment, hiding a hoard, and other “ritual” activities that might be imagined to confound a rational approach; already I feel the approach is unravelling a little. Perhaps classifying holes in the ground by motivation is pushing the concept of context description into the realm of New Archaeology.. Also, it does imply a quite remarkable level of understanding, or at least self-confidence, on the part of the archaeologist.
Besides ploughing, which is a usually self-evident,  most agricultural process happen on the surface, although the digging of beds for horticulture, and pits for trees can be easily overlooked.  Gardening can produce odd shaped holes, and can deploy a lot of stakes for plants such as beans or defining or protecting specific beds.
Effective waste disposal is an essential part of any culture, and in appropriate conditions this may involve holes in the ground.   What is interesting about this process is that that digging holes produces an equivalent volume of spoil, which itself has to be disposed of.   Quarrying for material, such as daub or stone, used in construction of a building can provide ready-made holes for disposal of rubbish for the initial occupants, demonstrated again simplistic ideas about motivation are not helpful.
Ancient buildings heated by open fires which generate considerable quantiles of ash, as well as other materials from regular cleaning.  In addition, any built environment used by humans or animals will generate waste, and provision its disposal should be a prior consideration of the basic design.
There should be a lot more to say about burials; not a typical day for those involved, and frankly, all those little bones, very fiddly.  Besides, residences for the dead are specialised built environments that don’t have to obey normal rules of form and function, interesting but not typical. 
The point I am trying to rescue is that digging holes is actually a relatively unusual activity, and within any form of stratified society would normally be considered to activity undertaken by a specialist.  
While who digs holes, and individuals’ proximity to rubbish might in certain contexts be regarded as an interesting social indicator, it is not information normally available through this type of archaeology.  
Parts of hunting forest, a space reserved for elite entertainment, may be defined by a bank and ditch which is engineering, or at least requires an engineer; someone has make a series of very specialised decisions.   
A section of Hadrian's Wall; the effect of engineering on the Landscape.
I do not wish to imply some sort of truism to the effect that digging in the ground is engineering, but simply note that most of the significant man-made features the landscape are the result of engineering or actions under the technical control of an engineer.    Clearly, this is engineering in a broad sense, encompassing what we think of as civil engineering, architecture, and surveying. 
Thinking outside the box
A key theme is about how to think in a fluid rather than crystalline manner; the latter is tick box thinking, the former is the provision of a box marked none of the above; if you think you know what you are looking for you are pretty much doomed to finding it.
I think you can regard the primary function of the archaeologist as recording what is being destroyed through the process of excavation; beyond that, particularly the nature and quality of any interpretive report, expectations are more flexible.
Where stratigraphy is present you always have some framework, but if everything is sealed by 20th plough soil and cut into periglacial deposits, it can be difficult to know where to start.   As a result many reports don’t progress much beyond identifying those aspects of the site that correspond in some way to previous discoveries elsewhere.  Thus, by most standards, our reliance on comparative methodologies is highly susceptible to both sample and observer biases, which helps create many circular arguments in our understanding of this type of archaeology.
I would observe some archaeology is recorded in in somewhat peremptory tick box manner; taking a few samples and recovering finds which some hopefully some clever person will in a lab explain later.   The boxes being ticked for context descriptions with words like pit, posthole or gully are often sufficiently vague, generic and misapplied that they do not encourage further thought on the matter.   The persistence of ideas like “Drip Gullies” demonstrates an inability to escape from the futile circularity of finding what other people have found.   Such concepts become so embedded in the literature as to be invulnerable to rational deconstruction.   [1]
Above; a section of the Orsett Multi-period site showing MIA to Saxon features
Theoretical structural archaeology was an approach designed to extract value and meaning from archaeological data sets, by trying not to tick boxes, but by understand holes in the ground as engineering where appropriate. 
In this approach it is important to think in terms of built environments rather than buildings. While it is perhaps customary to break these down into categories such as agricultural, military, industrial, or domestic, it is fairly obvious many types of archaeology encompass several, even all of these functions.
It is through engineering that the environment is conditioned and transformed to allow sedentary agriculture, not just the cultivation and storage of crops, but also the protection of animals from predators, principle of which is often other humans.   The necessary technology to exploit these mid latitude environments had already been developed long before farmers tried to colonise these islands. 
Putting the ox before the cart
Consider, if you have a cart, then you also require a cart shed, with buildings for draught animals along with their food and bedding.  In addition, a paddock preferably with water supply, decent boundaries and gates would be useful, along with somewhere to put the muck.   However, if we have to accommodate a wagon rather than a cart, the built environment must be designed around its wider turning circle and the extended size of the vehicle with its team.  [Left; Baden culture Neolithic model wheeled vehicle] A wide variety of different engineered environments have to be accessible to particular types of wheeled vehicles and also require buildings of this type; somewhere there is a building where these vehicles were made and maintained. 
The ergonomics of non-mechanised farming are inherent in the limitations of Human labour and that of draught animals that remain generally true into historical period. 
Fluid structural thinking on the level
In a complex archaeological dataset with no stratigraphy and lots of postholes, identifying an individual engineered structure is likely to involve not knowing what you are looking for.  It is a bit like code breaking, in that you need an insight or a crib; knowing the original language is important, as this has to conform to certain rules.  What is important about engineering is that fundamentally, it is maths, so can be understood as such, it has rules;  you can even model a pile of soil. 
However, the most important diagnostic characteristic of an engineered structure is usually depth of its archaeological features.  the foundations of buildings are usually level, although in more complex structures the taller or substantial parts of a structure deeper foundations.
There natural preference to think about archaeology in plan view, but important information about structural relationships can be encoded in the original depths of features.
Modelling built environments requires a culturally appropriate understanding of local traditions particularly in terms materials, their properties, limitations, and the practicalities of their use.  The modelling of theoretical superstructures should consider the nature of materials, particularly the taper in timber.  Models of individual buildings should consider provision for appropriate light heat and ventilation, as well as drainage as these are often implicit the structural design.
While all of this is fairly simplistic by engineering standards, is actually about mind-set, and the ability, strange though it may seem, to see without looking; to be able to evaluate data without too much prior assumption or expectation is the hardest aspect of thinking like a structural archaeologist.

[1] So, just for the record; the idea that water dripping from a roof can erode a self-contained penannular feature is false, since it fails to explain where the original soil, with its inclusions, went to, and why, in this particular period of the Iron Age, water no longer goes downhill under gravity. 
In other words. where does the run off from a modest roof, robbed of its momentum by its initial collision gets sufficient energy to penetrate into the subsoil, displacing a significant volume of earth, including inclusions like stones to leave a remarkably regular cavity several feet deep?  
These features are foundation trenches for walls.