Are there any probable cases of laryngeal alternation? I'm not aware of any. Radical consonants (which the PIE laryngeals probably were) can be stable under cer

Are there any probable cases of laryngeal alternation? I'm not aware of any. Radical consonants (which the PIE laryngeals probably were) can be stable under certain conditions and unstable under others - they seem to be less stable in Germanic than in Semitic or Northwest Caucasian, although Germanic /k/ is stable... but Polynesian /k/ isn't. IMO the best guess at this point is that the PIE laryngeals were stable until they disappeared Confirmation in historical linguistics is probabilistic. Sound laws can't be demonstrated the way "the sun is up" can be, but there's a great deal of evidence for Grimm's and Verner's Laws, less evidence for Cowgill's, and even less for things like the "pibati rule" or h1 preservation in Albanian. (I'm skeptical of the pibati rule - the root is irregular in some branches anyway, and it could be dissimilation or an exception to the loss of b or something.) The root composition rules are a little more complicated than that - you can have TeT or DheDh, but not TeDh, DheT, or DeD. Laryngeal preservation in Germanic is a pretty extraordinary claim. Are there other cases of this?