Abstract
Detecting C(4) plants consumption is central to investigating animal ecology, agriculture, dietary transitions, and socio-environmental adaptations, and can be done using carbon isotope analysis. The conventional δ¹³C threshold used to identify C(4) plant intake does not consider substantial ecological variability across Europe. By analyzing over 4,000 δ (13)C values from archaeological C(3) and C(4) grains, we present a European-wide C(3) grain δ (13)C baseline and establish adjusted δ (13)C threshold estimations for C(4) consumption from the site to the ecozone scale using multicomponent environmental models and ecozone cluster analysis. We show that a fixed threshold lead to under- or overestimation of C(4) plant consumption, particularly in northern/humid and southern/arid regions, where the threshold needs to be revised downwards or upwards by up to 2‰. This refined framework offers a more accurate baseline for interpreting human and animal diet and enhances our understanding of the spread, adoption and consumption of C(4) crops across Europe.