19 October, 2008

1. What is the evidence for the built environment in prehistory?

The surviving evidence for the ancient built environment mainly consists of postholes. These are the archaeological remains of small pits dug into the ground to accommodate timber posts, typically 0.20 –0.40m in diameter and of similar depth. Postholes are a type of feature, a term archaeologists use to describe the individual impressions left in the ground by people digging holes in the past. Other common types of features are pits, ditches, and gullies.

An archaeological site plan from Orsett in Essex, showing a complex pattern of postholes, ditches, and gullies [1].

The significance of postholes to archaeology lies in the fact that posts, rather than walls, were the principle load-bearing component of buildings and structures in prehistory. The presence of postholes is therefore indicative of buildings and other structures on archaeological sites of this period. The study of these small holes in the ground, usually devoid of finds, is central to this research and to our understanding of several thousand years of our built environment.

In terms of the archaeology of Southern England in the First Millennium, postholes are probably the commonest single feature found on archaeological sites, and a reasonably sized site may have several hundred. However, it’s not hard to establish that the majority of postholes that have been excavated were not understood, and usually no explanation for their presence was ever put forward. It is not simply that familiarity breeds contempt, but that postholes are actually quite difficult to understand.

Most of the archaeological sites of interest to this study are rural, and agriculture, particularly ploughing, disturbs the soil, destroying all but the deepest features. As a result, excavations seldom find the floors or walls from ancient buildings. It is usually only the foundations, in the form of postholes, that remain to be excavated.

Ploughing destroys most of the ‘stratigraphy’ of a site; that is, the sequence of layers that indicate in what order they were deposited and from where features were dug. The popular concept of archaeologists digging down through the layers to get to the earliest period simply does not apply on this type of site.

However, even when you have excavated and recorded the surviving features, understanding what they represent is far from straightforward. The following are some of the more obvious problems that contribute to making this a complex problem:

  • Several phases of building activity may be superimposed;
  • No stratigraphical sequence survives;
  • Later features can destroy earlier features;
  • Features may be not be recognised, & therefore are missed;
  • The excavation may only uncover part of the structure.

A simplified archaeological site plan showing how features are typically represented.
These factors create a complex puzzle, but it is one for which we have a partial solution, and there are types of buildings and structures that are routinely recognised from postholes. The real problem is what to do with those postholes that do not appear to fit the patterns of structures we already know, since, by definition, these must relate to structures we do not yet know about.
Thus, probably the most fundamental problem is: How do you look for types of structures that you don’t yet know exist?
This is where it starts to get interesting.
[1] G. A. Carter, 1998: Excavations at the Orsett ‘Cock’ enclosure, Essex, 1976. East Anglian Archaeology Report No 86.