u/an_05

In the Dravidian languages, words ending in hard stop consonants necessitate an enunciative (release) vowel, but the way this vowel is represented in modern times is very different. In Tamil grammar, this release is considered to be a ½ maatra — that is, a very short, high-back unrounded vowel called kurriyalukaram ([ɯ] or [ɨ]). In Telugu, on the other hand, the same release is given a full 1 maatra and is produced as a fully rounded [u]. Although there is this clear difference in phonological weight and lip position, both forms stem from a common ancestral mechanism for dealing with unreleased consonants.

The best indication of the actual nature of this vowel is its behaviour in sandhi (the combination of words). Whether it is the ½ maatra [ɯ] in Tamil or the 1 maatra [u] in Telugu, this vowel is essentially weak. When a word ending in this enunciative vowel is followed by a word that begins with a true vowel, the enunciative vowel disappears altogether in order to avoid a hiatus (for example, in Tamil, kāṭu + araṇ = kāṭaraṇ). This consistent omission shows that, historically, it was never a genuine lexical vowel that carried meaning, but rather an epenthetic structural vowel serving to break up illegal consonant clusters.

Given its weak nature, one might be inclined to regard the almost non-existent Tamil kurriyalukaram as the original Proto-Dravidian release, but historical orthography shows that this is not the case. When the Tamil scribes adopted the Brahmi script, they introduced the puḷḷi (dot) expressly in order to suppress the inherent vowels and thus write consonants only. If the Tamil word-final release had still been merely an original, featureless breath, the scribes would have simply written words such as kāṭu (forest) as kāṭ with a puḷḷi. The fact that they deliberately omitted the puḷḷi and instead used the 'u' grapheme (காடு) proves that the sound had already passed over into the phonological system; it had developed into a distinct, marked phonetic segment ([ɯ]) which the native speakers recognised and for which they required a visual representation.

Since neither the present-day Tamil nor the Telugu forms correspond to the original state, well-known Dravidian linguists such as Kamil Zvelebil and David McAlpin suggested an alternative approach. They proposed reconstructing for Proto-Dravidian an underspecified, neutral vocalic release—which in effect was a mid-central schwa [ə]. In the roots of Proto-Dravidian, this was not actually a distinct vowel phoneme but simply a microsecond of pure voicing with the mouth in a resting position, serving as a natural, biomechanical release for hard stop consonants.

In order to understand how the modern languages have diverged from this ancient schwa, it is necessary to acknowledge a clear three-way difference in the way the lips are positioned: actively pursed [+round], actively spread or tense [-round], and completely at rest/neutral [0 round]. The original PDr schwa was indeed a true zero-state (0 round). Starting from this neutral state, the various branches that developed took parallel but opposite evolutionary routes. In the case of South Dravidian (Tamil), the strong stops at the back of the mouth (such as -k and -ṭ) caused the tongue to be raised and moved back, at the same time the lips changed from the neutral [0 round] position to a tense, unrounded [-round] one, resulting in the formation of [ɯ].

On the other hand, the South-Central branch (Telugu) never went through this unrounded intermediate stage at all. Because of the natural tendency for bilabial consonants (such as -p) to attract one another, the speakers of Telugu moved the neutral schwa directly into a completely pursed [+round] position. It is obvious that the tongue movement and lip movement occur in a coarticulatory fashion, that is in an independent and simultaneous way.They then applied this rounded [u] uniformly to all the consonants in order to establish a neat and consistent phonological rule, and in the end had the orthography adopt it as a full 1 maatra vowel. Since both of the present-day developments can be traced back directly to a neutral [0 round] schwa, this provides a beautiful explanation of the current differences—and fully accounts for the fact that the unrounded -u is completely missing in Telugu and the other branches.