lpetrich
Contributor
His method seems to me too hand-wavy, so that's why I bumped it down.Greenberg and his disciples regard Amerind as very well-supported, certainly higher than Austric or Nostratic.
Problematic Use of Greenberg’s Linguistic Classification of the Americas in Studies of Native American Genetic Variation - PMC
Excrement, night, grass -- all dark-colored.Whereas Greenberg’s classification has been widely and uncritically used by human geneticists, it has been rejected by virtually all historical linguists who study Native American languages. There are many errors in the data on which his classification is based (Goddard 1987; Adelaar 1989; Berman 1992; Kimball 1992; Poser 1992), and Greenberg’s criteria for determining linguistic relationships are widely regarded as invalid. His method of multilateral comparison assembled only superficial similarities between languages, and Greenberg did not distinguish similarities due to common ancestry (i.e., homology) from those due to other factors (which other linguists do). Linguistic similarities can also be due to factors such as chance, borrowing from neighboring languages, and onomatopoeia, so proposals of remote linguistic relationships are only plausible when these other possible explanations have been eliminated (Matisoff 1990; Mithun 1990; Goddard and Campbell 1994; Campbell 1997; Ringe 2000). Greenberg made no attempt to eliminate such explanations, and the putative long-range similarities he amassed appear to be mostly chance resemblances and the result of misanalysis—he compared many languages simultaneously (which increases the probability of finding chance resemblances), examined arbitrary segments of words, equated words with very different meanings (e.g., excrement, night, and grass), failed to analyze the structure of some words and falsely analyzed that of others, neglected regular sound correspondences between languages, and misinterpreted well-established findings (Chafe 1987; Bright 1988; Campbell 1988, 1997; Golla 1988; Goddard 1990; Rankin 1992; McMahon and McMahon 1995; Nichols and Peterson 1996).
While there are plenty of odd semantic shifts that have happened, it is best not to rely on them to assess language relationship, because they make relationship hypotheses difficult to falsify.
One should avoid using them outright or stick to very common ones.