This chapter discusses the movement of people, trade goods, and ideas between 3500 BC and 259 BC. It focuses on how geographical features like seas, rivers, and mountains influenced the movement and interactions of groups like the Indo-Europeans. The Indo-Europeans originally lived near the Caucasus Mountains but migrated for reasons like overgrazing or invaders, spreading their languages and influencing modern civilizations across Europe and Asia. Their migrations and the Aryan caste system they developed are examined.