Roman imperialism brought about interconnected world history. So argues the second-century historian Polybius. Beginning in the 140th Olympiad (220-216 BCE), “history became corporeal, so to speak, [hoinoei sōmatoeidē] and Italian and African affairs were woven together with those in Asia and Greece, and the direction of everything became towards one end [telos]” (1.3.4). The rise of Rome marks a historical threshold: the first truly “world” empire and a moment of unification for world history. This talk sets Polybius’ organicist claims about Roman empire in the context of Hellenistic historiography, and examines some aspects of Polybius’ reception history in later Roman historical writing. In so doing, I trace a long tradition of using corporeal metaphor to theorize the intersection of world empire and effective historiography.