Three-Way Contrast of Secondary Articulations in PIE

[David L. White]

>> My proposal makes the most sense within a wider context where _all_
>> (pre-)PIE consonants had labialized (and palatalized) variants.  This
>> would be comparable to the developments that can be seen later in Old
>> Irish (3-way split between "slender", "broad" and "u-coloured"
>> consonants) or in Tocharian.  The Tocharian case (where *i, *u and *e
>> merged as *@ (*a"), or rather: *e > *@, *i > *(y)@, *u > *(w)@) is
>> especially interesting, given the lack of *i and *u in PIE
>> [full-grade] root structure (so maybe **CiC > *C(y)eC, **CuC >
>> *C(w)eC).  As was the case in Old Irish and pre-Tocharian, such a
>> system with a 3-way opposition was inherently unstable, and was
>> eventually resolved leaving a number of irregularities.

        I don't know about Tocharian (the only source available to me here
speaks of a two-way contrast), but for Old Irish the idea that there was a
three-way contrast has certainly been disputed, notably by Green.  Green
notes that such a system is not attested (as far as I know this is true)
among living languages, and proposes instead that Old Irish labialization,
which occurs only in codas, is better analyzed as a series of short
diphthongs in /-u/.  Unfortunately this proposal is hardly an improvement,
since short (mono-moraic) diphthongs (as opposed to contrast between
bimoraic and trimoraic diphthongs) are also not known to be real (in living
languages), and even if real are not known to occur with secondary
articulations, for (dare I say it) fairly obvious phonetic reasons:
secondary articulations basically _are_ (or can be) short diphthongs, in
terms of mundane phonetic realization, and it would indeed be difficult to
keep them apart.  The phenomenon of intrusion (by which these vowel-like
consonantal qualities get into the vowels) is very real, as can be seen both
from modern spectrograms and historical sound changes.

        But Green also asserts that labialization is morphologically
predictable in Irish, occuring only (if I am remembering correctly) in the
dative singular of /o/-stems and in some 1st singular verbs, in both
instances from previous /-o/, it would seem.   (By way of /u/?)  So the
question occurs:  are there any unequivocal examples of contrast between
/a/-quality and /u/-quality in Old Irish?  Or Tocharian?  Or PIE?  It surely
serves no point to multiply the number of consonantal phonemes in PIE by
something close to three if no contrasts can be adduced, not to mention if
the system posited is for good reason (as opposed to mere "typology")
suspected of being phonetically unviable, or something very close to it.

Dr. David L. White