[1] Based on Frachtenberg's observations, Edward Sapir (1921) included both Takelma and Kalapuyan in his extended version of the Penutian "stock", listing them however as individual members without positing a special relationship between the two.
[2] The first explicit proposal for a family comprising only Takelma and Kalapuyan (as member of the Penutian "stock") was made by Morris Swadesh (1965) in a lexicostatistic study, who found a lexical similarity of 48% between Takelma and Kalapuyan,[3] although this figure was based on rather bold assumptions about lexical matches.
[4] Shipley (1969) made the first attempt towards establishing regular sound correspondences by strictly applying the comparative method, and listed sixty-five preliminary reconstructions for "Proto-Takelman".
[9] In an unpublished, but widely cited conference paper, Tarpent and Kendall (1998) critically evaluated the evidence for Takelma-Kalapuyan, and concluded that a grouping which exclusively comprises Takelma and Kalapuyan is not justified, and that features shared between the two have to be assessed in a wider Penutian context (a similar position was taken before by Silverstein (1979)).
This event is possibly related to archaeological evidence of a transition in the material cultures of the Rogue Valley that occurred around 300 CE, from the "Glade Tradition" to the "Siskiyou Pattern".