Soils have been a vital part of the earth for millions of years and for several thousand years have supported the developments of mankind. Soils often bear the imprint of occupation of the land by humans, plants and animals and there are many examples where the nature of the soil and its constituents have been used to help understand the complex history of earlier life on earth; this is the role of the archaeologist.
Over many centuries soils have been used for a variety of purposes, particularly farming and settlements. Many of these uses of soil have left their mark in the soil and this mark is of great interest to archaeologists and others who are interested in the past use of the soil and in the peoples that lived on the land at the time. The discovery of artefacts, treasure and evidence of past human occupation in the landscape is fairly common - often by the farmer who may plough up some historical objects, the builder or excavator who unearths evidence of previous settlements when preparing a site for roads or buildings, and the treasure trove hunter who, with their metal detector, searches land for buried treasure.
Soils varies in their ability to preserve artefacts, treasure and evidence of human occupation. The decomposition of organic remains, such as bodies, in wet poorly drained soils, tends to be much slower than in dry soils. Thus in wet soils, particularly peaty and boggy ones, ancient animals and humans have been found in a good state of preservation and have been able to throw much light on the period of history to which they belong. Even the clothes worn by humans have been preserved in these environments, for over many hundreds of years in some instances. In addition, many wooden constructions, relating for example to houses, ditch linings, and boats have been preserved in these conditions. In well-drained soils, organic remains decompose more rapidly and in these soils well preserved organic remains are more uncommon. In contrast metal objects survive better in the aerated conditions and ornaments and weapons have been found well preserved in such soils. Acid soils can be more aggressive in decomposing artefacts than more neutral soils. Iron objects in particular are at risk from soil acidity. Pottery, however, tends to be reasonably stable to decomposition in soils of all types.