The steppe and the forest-steppe zones of Siberia represent an environmental belt that links the outskirts of western Asia and Eastern Europe. This corridor of northern regions of steppe and forest steppe has contributed towards the dispersal of animal and crop species, metals, precious stones, as well as new technologies across Eurasia in prehistory (Kuzʹmina, 2008; Koryakova and Epimakhov, 2007). Dietary changes within the populations inhabiting the southwest Siberia and northern Kazakhstan in prehistory indicate changes in the economy, at the same time marking the beginnings of East-West interaction across northern Eurasia. Past palaeodietary research using stable isotope analysis have mainly focussed on pastoral cattle breeding populations of the Bronze Age period. The introduction of domestic animal species of the near Eastern origin, such as sheep and goats, dramatically changed the lives of the local population. It is crucial, however, to access the diets of humans and animals from earlier periods (Neolithic/Chalcolithic) in order to understand the timing and nature of dietary change during the Bronze Age of southwest Siberia and northern Kazakhstan. It has been implied from previous research suggesting that elevated δ13C or δ15N values in animals and subsequently in humans, for example, could be a result of climatic rather than dietary change. In this paper we discuss the timing of pastoralism in the southern zones of western Siberia (Upper Ob River) and northern Kazakhstan (Tobol River basin) by presenting the stable isotope results of the Neolithic to Bronze Age humans and fauna. This data, combined with the AMS radiocarbon dating results, allows us to detect human dietary change through time http://mc.manuscriptcentral.com/holocene HOLOCENE