SS.6.3: EARLY RIVER VALLEY CIVILIZATIONS IN THE EASTERN HEMISPHERE (ca. 3500 B.C.E. – ca. 500 B.C.E.): Complex societies and civilizations developed in the Eastern Hemisphere. Although these complex societies and civilizations have certain defining characteristics in common, each is also known for unique cultural achievements and contributions. Early human communities in the Eastern Hemisphere adapted to and modified the physical environment.