23 October, 2008

3. How do archaeologists recognize buildings and structures?

Let us be perfectly clear from the outset: the foundations of prehistoric buildings were not continuous, being formed by intermittent posts. In more modern buildings, the foundations are usually continuous strips set in the ground, marking the position of ‘load-bearing walls’. Since all the elements of the modern foundation are joined together, it is easy to understand the plan of the building. However, working out which posthole goes with which prehistoric structure, often without evidence of walls and floors, is not easy. In fact it is very difficult, and in many instances, probably impossible.

Part of the site at Mucking, Essex [1], a collection of postholes so complex that it prompted the excavators [2] to compare it as a palimpsest – an ancient document that has been overwritten several times.

The buildings and structures on archaeological sites are usually recognised as a spatial patterns or arrangements of posts and other features. It is very hard to escape the analogy of ‘joining the dots’, a staple of puzzle books. Postholes appear on a plan as dots, and joining them up to make a building or structure is the name of the game. Sadly, in archaeology, the dots are not numbered in sequence, and there is no solution at the back of the book.

The key issue clearly is: What constitutes an acceptable or recognised pattern of posts? The answer lies in ‘comparative methodology’, one of the most important ways archaeologists routinely think about what they find.

To help understand the things they unearth, archaeologists look at similar finds from other sites. For example, comparing the pottery between sites allowed the development of a system of relative dating based on pottery styles. Archaeology is heavily dependent on comparing sites and finds, and finding ‘parallels’ – similarities between objects and structures -- is at the root of much our understanding of the past.

The same is applied to postholes: we tend to look for structures identified by other excavators on similar sites. At first glance, this is a practical solution and consistent with the general methodology of archaeology. Given the ephemeral nature of the evidence, this is a very robust method of identifying structures; if we all have the same types, then there is little room for doubt as to the veracity of the identification.

However, the problem lies in what to do about those features we don’t understand, which are not part of the patterns we are looking for. In numerical terms these may often be the majority of the excavated features.

In the excavation report, an excavation will be divided into ‘phases’. Each phase contains features of a similar age, based on:
  • Finds, such as pottery;
  • Stratigraphic relationships;
  • Scientific dating methods;
  • Being part of a (dated) structure;
  • Alignment of the feature.
Those features without such criteria are referred to as ‘unphased’, and usually warrant little attention in the report, regardless of the quantity of features. The narrative invariably, and quite naturally, concentrates on what can be interpreted, and can have little to say about what was not understood.

In the final report, only the most significant postholes will warrant a description in the text, and the rest will only make an appearance on a plan showing all the features of a particular phase, a ‘Phase plan’. However, people don't tend throw rubbish into postholes, and thus finds may be ‘residual’, i.e., the material already in the soil when the posthole was dug. For this reason, postholes are often erroneously placed on the phase plan for an earlier phase than the one in which they were actually dug.
In essence, what is being suggested here is that archaeologists interpreting this type of posthole data do so on the basis of looking for the same patterns that other people have found elsewhere, and evidence that does not fit with what has been found elsewhere will be largely ignored.

This is may be regarded as a contentious statement. But if true, it raises questions about the soundness of such a methodology and the results it generates. Granted, it is an oversimplification, but as we shall see, this approach is explicit in many reports, and implicit in others, and it seriously impacts on our understanding of the prehistoric environment. Manuals of field archaeology do not describe this approach, but neither do they propose an alternative method of understanding postholes. This is a very difficult problem.
There are several matters arising from this idea of looking for ‘recognised patterns’:
    • What are these accepted patterns?
    • If archaeologist A looks for what archaeologist B has found, and B was
      looking for what C had found, etc, where does the chain begin?
    • Who started the chain?
Some of the answers to these and many other questions about this subject may be found in a place called Little Woodbury in Wiltshire, excavated by an archaeologist called Gerhard Bersu.[3] This is the subject of part 4 of this blog . . .
[1] D. Bond (1988), 'Excavations at the North Ring, Mucking, Essex'. EAA Report No.43; Archaeology section ECC
[2] M. U. Jones & W. T. Jones (1975), 'The crop-mark sites at Mucking, Essex, England'. In: Bruce-Mitford, R., ed. Recent archaeological excavations in Europe. Routledge Kegan Paul, London, pp. 133 -187.
[3] G. Bersu (1940), 'Excavations at Little Woodbury, Wiltshire. Part 1, the settlement revealed by excavation.' Proceedings of the Prehistoric Society, pp. 6, 30-111.