A journey into the landscape of past feeding habits: Mapping geographic variations in the isotope (δ15N) -inferred trophic position of prehistoric human populations

Abstract

Stable isotopes of nitrogen (δ15N) provide information that can be used to calculate, in a quasi-continuous manner, the trophic position (TP) of organisms within particular food webs. The estimation of the TP is fundamental to analyze cases in which some degree of omnivory is involved. Humans, as a species, are trophic omnivores that use plant and animal tissues as food sources, although in an intraspecific context they tend to significantly vary in their respective degree of omnivory. In archaeology, the use of stable isotopes to infer past diets is widespread; however, the formal assessment of TP is rare. In this paper we describe a method to simultaneously calculate and map the TP of past human populations across large spaces, involving wide environmental variation. This method uses, as inputs, δ15N isoscapes corresponding to (i) primary producer/s, (ii) a taxon of primary consumers with wide spatial distribution and (iii) humans. The first two isoscapes function as the needed baselines for TP calculation. The approach is exemplified with data from central and southern Argentina and Chile (southern South America, 30°–56° S).