In archaeology, natural is a term to denote a layer (stratum) in the stratigraphic record where there is no evidence of human impact on the environment.
In addition, through the development of geoarchaeology, scholars believe the natural landscape has a bearing on interpretation of subsequent human activity on any given site.
On urban sites, where research interests may make a detailed examination of the earliest part of the record impractical, rudimentary human or prehistoric activity may go unrecorded, as opposed to an equivalent horizon on a rural site for which the study team's agenda is to look for prehistoric evidence.
Chemical and soil process over time often obscure and cause decomposition of cultural materials, and thus a human-occupied layer may look natural.
Additionally, early prehistoric tools were manufactured from natural materials, such as bone, stone and fiber; they do not stand out as clearly as metal, glass and plastic.