Book excerpt: Nowhere on Earth is there an ecological transformation so swift and so extreme as between the snow line of the high Andes and the tropical rainforest of Amazonia. Because of that, the different disciplines that research the human past in South America have tended to treat these two great subzones of the continent as self-contained enough to be studied independently of each other. Objections to that approach have repeatedly been raised, however, warning against imagining too sharp a divide between the people and societies of the Andes and Amazonia when there are clear indications of significant connections and transitions between them. Rethinking the Andes-Amazonia Divide brings together archaeologists, linguists, geneticists, anthropologists, ethnohistorians, and historians to explore both correlations and contrasts in how the various disciplines see the relationship between the Andes and Amazonia, from deepest prehistory up to the European colonial period. This collaboration has emerged from an innovative program of conferences and symposia conceived to generate discussion and cooperation across the divides between disciplines.