What if the deepest resources for globalizing IR lie not in capitalist modernity, but in humanity's much older struggles against hierarchy? This Element argues that Global IR cannot become genuinely anti-Eurocentric unless it breaks decisively with 'methodological presentism': the tendency to read the past in terms of the present. Engaging Global IR debates, and drawing on Karl Polanyi, Political Marxism, and evolutionary anthropology, the book offers a non-presentist macro-historical narrative. It mobilizes deep history to trace the millennia-old human capacities to refuse domination, pursue autonomy, and sustain cooperation, thereby inviting readers to fundamentally rethink the sources of human interconnectedness and solidarity. On this basis, it proposes 'radical modernity', rooted in the prehistoric legacy of 'radical egalitarianism', as an alternative to capitalist modernity. Radical modernity is not a Western achievement later diffused to the non-Western world, but an alternative foundation for rethinking universality, difference, and the 'international' from below.