The F31 Bantu languages of north-central Tanzania Nyilamba and Ihanzu do not feature labiodentals. This is remarkable in that all of the other languages of the intermediate genetic grouping to which Nyilamba and Ihanzu belong -- the Takama branch -- feature labiodentals robustly. With a specific focus on Ihanzu, this talk describes the lack of labiodentals in this language as a direct result of contact with the language isolate Hadza. Following a brief introduction to the Ihanzu language and its larger context, the talk reviews lexical comparative work in Masele (2001) to establish that, though every language of the Takama branch developed labiodentals independently either through sound changes or via the borrowing of lexical items, Ihanzu did not. This preservation of older structures is attributed to the existence of a parallel structure, that is, a lack of labiodentals in the phonemic inventory in the contact language Hadza. In order to attribute this preservation of a system lacking labiodentals to contact with the language isolate Hadza (which currently features the labiodental [f]), the talk establishes the adoption of [f] as a relatively recent effect of Hadza contact with the South Cushitic language Iraqw, and argues that at the time and place of the relevant contact with Ihanzu, Hadza did not feature this phoneme. Additional non-linguistic evidence of the nature of Ihanzu-Hadza contact is provided from oral histories, origin stories, and descent patterns of both the Ihanzu speaker community and the Bantu-speaking peoples of the wider region.In the context of this workshop, the talk provides a clear-cut example of the effects of a non-Bantu language (Hadza) on the sound inventory of a Bantu language (Ihanzu), within the larger ecology of the complex interchanges occurring in the Tanzanian Rift Valley Area. In addition, the proposed contact is recent enough to serve as a concrete case study, but also old enough (i.e. pre-colonial) to require recourse to linguistic and other non-direct methods of observation, such as oral traditions.