However, contrary to current practice in historical linguistics, Sapir also often relied on "hunches" and "gut feeling" when proposing new language families.

Sapir entertained the idea that ultimately all languages of the Americas might turn out to be provably related and such a phenomenon as the apparent Pan-American tendency to have first person forms with a prefixed n- was suggestive for this line of thought.

Joseph Greenberg worked in the tradition of "lumpers" and following Sapir, was mindful of evidence not generally acceptable to those who hold that only actual linguistic reconstruction—through the comparative method—can yield reliable proof of genetic relationships between languages.

[12] This is based on Greenberg's *t'a'na "child", to which Ruhlen adds a masculine derivation *t'i'na "son, boy" and a feminine *t'u'na "daughter, girl".

[23] The 1960 proposal, in its outlines, was as follows: Below is the current state of Amerindian classification, as given in An Amerind Etymological Dictionary, by Joseph Greenberg and Merritt Ruhlen, Stanford University, 2007.