In this paper, I approach the choice of the language of study for a graduate research program. In a way, irrespective of the functionalist and generative warnings, I articulate the rationale for the choice of mother tongue language as the language of research by linguists. In the article, I caution that absence of existing research outputs is not a sound reason to allow straightforward research permit. Further, I point out that the main motivation of the selection of a research topic could be the contribution to an ongoing research in which the mother tongue of the researcher is staged to offer good evidence in favour or rejection of the existing claims available in the literature. This is the tradition in the scientific inquiry. Furthermore, I argue that comparative works can also engage the cluster of the languages to which the mother tongue of the researcher is affiliated. The motivation for the choice of the cluster should be to examine genetic affiliation rather than to allow the researcher to attract easy data collection practises. In the end, I open a discussion for more research on endangered languages of Tanzania, which is an open linguistic research area left to foreigners to date. However, I argue that an interplay of documentation and theory should be realised.