Nitrogen isotopes and the trophic level of humans in archaeology

Human and domesticate animal bone collagen delta N-15 values in prehistory differ generally by 3 parts per thousand or more from Neolithic to post- Roman times in Northwest Europe, leading to an assumed dietary animal protein fraction of 60-80% using a standard interpretation of delta N-15 values. We examine the assumptions on which this model rests and the limitations of our knowledge in the analysis of delta N-15 values in archaeology. We have developed a set of models which, with small changes made in assumptions (on the order of 17,,), can produce substantially lower estimates of the dietary animal protein fraction for given delta N-15 values. We consider the implications of various dietary animal protein fractions on agricultural carrying capacities and human population densities in prehistory. (c) 2006 Elsevier Ltd. All rights reserved.