This paper addresses the question of why the prehistoric Indonesian colonization of Madagascar has been described as the most astonishing fact of human geography. Evidence from linguistics, DNA, boat-building, and the history of trade is adduced to explain how and why such a colonization took place. It is argued that this colonization was made possible by the remarkable seafaring tradition that made Austronesian the world’s most far-flung language family in premodern times. Also of great importance was the strategic position of the states that organized this colonization with respect to an early world-system of the type described by Wallerstein.