Material evidence
Material evidence - objects and buildings made or used by people - is the backbone of archaeology. The two most common kinds of artefacts recovered by archaeologists are stone tools and pottery, because they are made of inorganic materials that do not decay, and therefore do survive. Archaeologists often divide pottery into four functional categories: table (or fine); cooking; storage/transport; and special (religious, industrial, etc.) In later periods, metal objects (including coins) and glass can also be preserved. Buildings made of durable materials such as stone and brick survive well; structures made of wood do not. Similarly, traces of textiles and baskets survive only in exceptional circumstances, such as the dry conditions of Egypt (the Tomb of Tutankhamun, for example).
 A memo and a black leather chair. © Photodisc Getty Images |
Simply finding an object is not enough, however: archaeologists need to establish a context for their finds. A group of artefacts found together is an assemblage, that is, there was some reason in the past for them to be associated.
Sometimes an assemblage is very clearly marked - the objects lie on a particular surface and are covered by a later, distinct layer. If so, the assemblage constitutes a sealed or stratified deposit. A site can consist of one assemblage, stratified or unstratified, or of many assemblages; it may or may not include architecture.
Archaeologists need to understand how an assemblage or site was formed, and what happened to the assemblage or site later on - in other words, to understand the site formation processes that affected the location and preservation or destruction of that site.