Tupi-Guarani languages are supposedly perfect examples of hierarchical indexing systems, where the relative ranking of A and P on the 1 > 2 > 3 person hierarchy determines the selection of the person markers. This chapter questions the relevance of the person hierarchy as a synchronic and diachronic explanation for such systems, with data from 28 languages. First, only SAP > 3 can really be posited in the actual languages, and second, it explains only part of the facts that it is supposed to account for in Proto-Tupi-Guarani. The chapter ends by suggesting that these systems do not result from the person hierarchy as a functional motivation. Instead, they may result from grammaticalization of pronominal paradigms lacking third-person forms.