New findings and interpretations concerning the genesis, functioning, and final development of three cultures in the forest Trans-Urals region have been examined: the incoming Gamayun culture (X–IV centuries BC), the local Itkul culture (VII–III/II centuries BC), and the heterogeneous Iset culture (IX/VIII–IV centuries BC). The latter formed as a result of interaction between Gamayun groups (descendants of of taiga hunters and fishermen who came from the Konda and Lower Ob River basin, bearers of the Lozva and Atlym cultures) and communities of settled pastoralists from the Late Bronze Age Barkhatovo culture of the Lower Tobol region. The westward advance of Barkhatovo groups occurred during a temporary withdrawal of the interceding Mezhovka culture communities into the forest-steppe, driven by the search for copper ore deposits in the Ural Mountains. Southward migrations of the forest population were triggered by abrupt cooling and increased humidity at the beginning of the I millennium BC. The Itkul culture was formed by metallurgical clans that separated from late Mezhovka pastoralist groups. Intermediaries in copper trade with distant steppe and forest "ethnic groups" were representatives of the Iset culture. During the VI-IVcenturies BC, Gamayun and Iset groups became incorporated into Itkul society.