The Importance of Context in Archaeology

In my last post I mentioned the importance of context to archaeological research. That is, knowing PRECISELY where an object was found and its relationship to other objects in the archaeological record. 

The goal of archaeology is to understand past human behaviour and how that behaviour changes over time. The primary (and in some cases, the only!) source of evidence available to help achieve this goal is the archaeological record, or the material record of that behaviour.

So, how do archaeologists get from ruins, pieces of dirty stone and pottery and patterns of dark patches in the soil to an understanding of human behaviour in the past and how this changes over time?

This is where context is important!  

To recap from the last post - Excavation, the principal method of data acquisition in archaeology, involves the systematic uncovering of archaeological remains through the removal of the deposits of soil and other material covering them and accompanying them.

Two types of information can be gleaned during excavation:

a) human activities at a particular period in the past, and

b) changes in these activities from period to period

Very broadly, contemporary activities take place horizontally in space and changes in those activities occur vertically through time.

Key to understanding this are some principles borrowed from the field of Geology. Stratigraphy is the study of the layering (stratification) of rock formations (or strata). According to the Law of Superposition, where one layer overlies another, the lower of the two layers was deposited first. So, in effect, as you go deeper below the ground surface, you're also going further back in time:

Stratigraphic time scale by Ray Troll. The rock formations (and associated fossils) from the earlier eras are located further below the surface. Source Image here.

Key to understanding the history of an archaeological site is its stratigraphy, or the layering of sediments containing evidence of cultural (human) activity.

Stratigraphy within an archaeological site. The different layers (strata) appear as differing shades of brown. Source image here.

This evidence can come in the form of artefacts, ecofacts or features (Peregrine 2001).

Artefacts are objects that have been modified or manufactured by humans that can be collected and removed by a person from an archaeological site (but in most cases shouldn't!). Flaked or chipped stone tools, pieces of ceramic (fired clay) vessels, and glass bottles are just a few examples of artefacts commonly found at archaeological sites.

Ecofacts are natural materials associated with human activity. Typical ecofacts include the remains of plants (e.g. seeds, pollen grains) and animals (e.g. bones, shells) that have been eaten by people.

Features are archaeological remains that cannot be removed from their context at an archaeological site. Examples are pits, fireplaces and postholes. Rubbish pits, or middens, containing accumulations of artefacts and ecofacts, are a common (and often very informative!) example of an archaeological feature (if you want to do archaeology - you had better get used to the fact that you will end up digging through someone's garbage at some point!). When an archaeological site is destroyed, features are invariably destroyed with it, although artefacts or ecofacts within a feature may be sampled for further study. 

Context allows us to take artefacts, ecofacts and features and use them to build a picture that we can understand (Peregrine 2001: 23).

Archaeologists can demonstrate contemporaneity of activities by proving to their satisfaction through careful excavation of a site that relevant artefacts and features are found in the same context (e.g. in the same stratigraphic layer) and have not been disturbed since initial deposition into the archaeological record (i.e. that they are in primary context).

Although the contents of a lower strata are usually older than those of upper strata, which creates the potential for comparison to tell us something about how things changed over time at a particular site, this must not simply be assumed by the archaeologist!

The Law of Superposition refers only to the sequence of deposition of the strata, not always to the age of the material contained within (Renfrew & Bahn 2008: 108). Sometimes later material may have been introduced into lower strata by pits dug down from higher strata, or material may have been moved around by bioturbation (the activity of animals that burrow through the deposits, such as crabs or earthworms!) Identification of such circumstances requires careful examination and recording by a trained archaeologist.

When looters disturb a site, as in the cases of illegal 'nighthawking' discovered by English Heritage around Hadrian's Wall, hunting for rich finds such as nice vases, coins or historic period bottles, and shifting aside material they are not interested in, they destroy the primary context of all that material and destroy most of its archaeological value!

  

As I noted in my last post, the Heritage New Zealand Pouhere Taonga Act 2014 makes it unlawful for any person to modify or destroy the whole or any part of an archaeological site in New Zealand without the prior authority of Heritage New Zealand.

Thanks for reading,

Nick.

References 

Peregrine, P. N. 2001. Archaeological Research: A Brief Introduction. Upper Saddle River, N. J. : Prentice Hall.

 

Renfrew, C. & Bahn, P. 2008. Archaeology: theories, methods and practice (5^th ed.). London: Thames & Hudson.