This article presents results from interdisciplinary research among the Kuikuro of the Upper Xingu (Brazil). The project integrates linguistic, ethnographic and archaeological data as a means to reconstruct the processes through which peoples speaking languages of the three largest South American linguistic groupings (Arawak, Carib, and Tupi), as well as a language isolate (Trumai), came to create a unique social system: the Upper Xingu sociocultural complex. The article address the following questions: how did this system – spanning from the 9th century AD until the present and formed by peoples with distinct cultures and origins – come into being? Which cultural bases and historical circumstances led to its structuring? What role did language and multilingualism play in this process?