Recent scholarly attention on decentralized political systems and their capacity for creating durable egalitarian social worlds is challenged by the fact that historical data on such societies is often difficult to uncover. Such is the case for precolonial Africa. But, by virtue of their geographical expanse, political power, and durability, we know that effective decentralized political systems did in fact prosper throughout early African history. My project uses historical linguistics to uncover the undocumented history of one such decentralized group - the semi-nomadic and pastoralist Ateker people of East Africa. Communities speaking the Ateker sub-group of Eastern Nilotic languages began migrating south out of Sudan c. 1300, coming to command strong military and cultural influence in the present-day Uganda, South Sudan, Ethiopia, and Kenya borderlands by the 18th century. Historians usually link such instrumental political achievements to centralized governance, so the absence of authority figures such as chiefs or kings in Ateker history potentially upsets assumptions that centralization of power best explains effective and durable political complexity. Ethnographic evidence suggests that "age-sets," or ceremonial age-based associations into which Ateker-speakers were initiated as young adults, enabled them to pool investments in ritual practices, share grazing lands in an arid environment, and accomplish military and diplomatic coordination across large geographic spaces. Using linguistic data and oral traditions collected during a year of fieldwork, I will explore the question of how age-sets became key socio-political institutions among the Ateker. I anticipate that this research will necessitate the revision of current theories on the development of political complexity in precolonial African history, while also exploring the important role of age as a socially constructed category for African political history.