This article analyzes the kinship system of the Piro of Peruvian Amazonia as an autopoeitic system, that is, as a system which generates its own existential conditions. The central theoretical postulate is that kinship is a system of subjectivity, since the basic structures of human consciousness necessarily involve being conscious of an I amid others. One of the article's objectives is to provide schemata enabling symbolic anthropology to return to a fertile use of the notion of "human nature". The analysis departs from a narrative, "The Birth of Tsla", which encapsulates - in both the message and the pragmatic conditions of the myth's enunciation - the fundamental principles of Piro kinship; this is followed by an analysis of the ontogenesis of human beings, which reveals the constitutive role, in this ontogenesis, of language and alterity.