Palaeoenvironmental and Archaeological Implications of Isotopic Analyses (13C, 15N) from Neolithic to Present in Qazvin Plain (Iran)

Palaeoenvironmental changes since the sixth millennium B.C. in northern Iran have been assessed through isotopic studies of archaeozoological remains from three prehistoric sites. Good quality collagen has been extracted from more than 40 bone samples from wild and domestic herbivores, boars, dogs and humans belonging to Zagheh (sixth-fifth millennium cal BC, Neolithic), Qabrestan (fourth-third millennium cal BC, Cha1colithic) and Sagzabad (second-first millennium cal BC, Iron Age). There is no clear trend in decreasing collagen content with increasing age. The carbon isotopic composition of herbivore collagen indicates mainly a consumption of C3-plants, with a significant amount of C4-plants in some individuals. The amount of consumed C4-plants is correlated to increasing δ15N, suggesting that C4-plants are linked to saline environments. The δ15N and δ13C of wild herbivores seem to decrease with decreasing age, suggesting wetter conditions in Iron Age than in Neolithic times. However, domestic herbivores do not exhibit any trend, maybe because environmental conditions linked to human activity are less variable than natural conditions. Differences in herding practices may explain isotopic differences between cattle and caprine.