The glottalic theory is a hypothesis that Proto-Indo-European had ejective or otherwise non-pulmonic stops, , instead of the plain voiced ones, as hypothesized by the usual Proto-Indo-European phonological reconstructions.
A forerunner of the theory was proposed by the Danish linguist Holger Pedersen in 1951, but he did not involve glottalized sounds. While early linguists such as André Martinet and Morris Swadesh had seen the potential of substituting glottalic sounds for the supposed plain voiced stops of Proto-Indo-European, the proposal remained speculative until it was fully fleshed out simultaneously but independently in theories in 1973 by Paul Hopper of the United States and by Tamaz V. Gamkrelidze and Vyacheslav Ivanov of the Soviet Union.
The glottalic theory "enjoyed a not insignificant following for a time, but it has been rejected by most Indo-Europeanists." The most recent publication supporting it is Allan R. Bomhard and in a discussion of the controversial Nostratic hypothesis, and its most vocal proponents today are historical linguists at the University of Leiden. An earlier supporter, Theo Vennemann, has abandoned the glottalic theory because of incompatibilities between it and his theory of a Semitic substrate and loanwords in Germanic and Celtic languages. However, Martin Kümmel, although rejecting the ejective hypothesis as implausible, argues for a re-interpretation of these stops as implosive, comparable to the Leiden interpretation as pre-glottalized stops.
Traditional reconstruction
The traditional reconstruction of Proto-Indo-European includes the following stop consonants:
+ The Proto-Indo-European plosives (traditional)labialsdentalspalatalized velarsvelarslabialized velarsvoiceless stops voiced stops () breathy voiced stops
is parenthesized because it is controversial, at best very rare and perhaps nonexistent.
Historically, the inventory was not introduced as an independent proposal, but it arose as a modification of an earlier, typologically more plausible theory.
In the original Proto-Indo-European proposal, there was a fourth phonation series, voiceless aspirated , which was assumed to exist on the basis of what is found in Sanskrit, which was then thought to be the most conservative Indo-European language. However, it was later realized that the series was unnecessary and that it was generally the result of a sequence of a tenuis stop () and one of the Proto-Indo-European laryngeal consonants: , or . The aspirate series was removed, but the breathy voiced consonants remained.
Problems There are several problems with the traditional reconstruction. Firstly, the rarity of is odd from a typological point of view. If a single voiced stop is missing from a phoneme inventory (a 'gap'), it would normally be that is missing (examples including Dutch, Ukrainian, Arabic, Thai, and Vietnamese); on the other hand, if a labial stop is missing, the voiceless is the most likely candidate (examples including stages in the evolution of Irish, Japanese, and Arabic).
Secondly, there are few languages which have breathy voiced consonants but no voiceless aspirates and even fewer that simultaneously contrast breathy voice with full voice. Roman Jakobson has asserted that no such language is known; however, that is disputed by some linguists who oppose the theory. For example, Robert Blust showed that Kelabit, a language of the Sarawak highlands in Borneo, has a system of stops consisting of voiceless stops, plain voiced stops, and prevoiced stops with voiceless aspiration. This is similar to the traditional reconstruction of the stop series of Proto-Indo-European, which include voiceless, voiced unaspirated, and voiced aspirated stops. In any event, the traditional reconstruction remains a typological oddity.
Thirdly, a longstanding but unexplained observation of Indo-Europeanists about the distribution of stops in word roots is that it had long been noted that certain combinations of consonants were not represented in Proto-Indo-European words in terms of the traditional system: No root contained a sequence of two plain voiced stops: there were no roots of the type , which reflects a common cross-linguistic constraint against roots with two similar stops. No root contained both a voiceless stop and a voiced aspirate: roots of the type or were not attested. As the result of a sound shift from Pre-Proto-Indo-European, roots of this type are attested as instead. On the other hand, the plain voiced stops were compatible with either of the other two series: or were both possible.
The constraints on the phonological structure of the root cannot be explained in terms of a theory of unlimited assimilation or dissimilation since they display a radical difference in patterning between three sets of consonants, the stops, that ought to behave identically. Typologically, that is very odd.
Original glottalic proposal
The glottalic theory proposes different phonetic values for the stop inventory of Proto-Indo-European:
+ The Proto-Indo-European plosives (original glottalic)labialsdentalsvelarslabialized velarsuvularsvoiceless stops ejective or glottalized stops () voiced stops
In his version of the glottalic theory, Hopper also proposed that the aspiration that had been assumed for the voiced stops could be accounted for by a low-level phonetic feature known to phoneticians as "breathy voice". The proposal made it possible both to establish a system in which there was only one voiced series and to explain at the same time later developments in some Indo-European dialects that became Greek, Latin, and Sanskrit, which pointed to some kind of aspiration in the voiced series. Hopper also treated the traditional palatalized and plain velar dichotomy as a velar-uvular contrast.
Gamkrelidze and Ivanov and have posited that both non-ejective series (traditional and ) were fundamentally aspirated ( and , respectively) but had non-aspirated allophones ( and ). According to them, the non-aspirated forms occurred in roots with two non-ejectives because no more than one aspirate could be in the same root. To express the variability of aspiration, Gamkrelidze and Ivanov wrote it with a superscripted h: . Thus, an Indo-European (in which represents any non-ejective stop) might be realized as (attested in Indic and Greek) or as (attested in Latin). In contrast, traditional theory would trace a form attested as both and to an Indo-European . The advantage of the interpretation over the previous is circumventing the typological oddity of the language in having only voiced aspirates by identifying the voiceless non-aspirates of the traditional stop system () as voiceless aspirates (). Postulating the voiceless stops as aspirated finds support in helping to explain Grimm's Law, with these purported now-aspirated stops () evolving into Proto-Germanic . This would also be typologically similar to one of the more notable evolutions from Ancient to Modern Greek (with φ, θ, and χ respectively).
Consequences The phonation system proposed by the glottalic theory is common among the world's languages. Moreover, the revised system explains a number of phonological peculiarities in the reconstructed system. The absence of a labial plain voiced stop in the protolanguage now becomes an absence of a labial ejective , proportionally a rather more common state of affairs. The theory also provides a completely-coherent explanation to the patterning of the stop series in roots: In many languages that have glottalized consonants, there is a phonetic constraint against two such consonants in the same root. The constraint has been found in many languages of Africa, the Americas, and the Caucasus. In Akkadian, the constraint affected borrowed and inherited roots, and one of the two heterorganic emphatics undergoes dissimilation and appears as a simple (unmarked) consonant, which is known as Geers's law. If the "plain voiced stops" were not voiced, the "voiced aspirated stops" were the only voiced stops. The second constraint can accordingly be reformulated as: two nonglottalic stops must agree in voicing. Since the glottalic stops were outside the voiced/voiceless opposition, they were immune from the constraint on voicing agreement in (2).
Decem and Taihun In 1981, Hopper proposed to divide all Indo-European languages into Decem and Taihun groups, according to the pronunciation of the numeral '10', by analogy with the Centum-Satem isogloss, which is based on the pronunciation of the numeral '100'. The Armenian, Germanic, Anatolian, and Tocharian subfamilies belong to the Taihun group because the numeral '10' begins with a voiceless t in them. All other Indo-European languages belong to the Decem group because the numeral 10 begins with a voiced d in them. The question then can be framed as which, if either, of the groups reflects the original state of things and which is an innovation.
Direct and indirect evidence
While the glottalic theory was originally motivated by typological argument, several proponents, in particular Frederik Kortlandt, have argued for traces of glottalization being found in a number of attested Indo-European languages or the assumption of glottalization explaining previously known phenomena, which lends the theory empirical support. (Similarly, the laryngeal theory was proposed before direct evidence in Anatolian was discovered.)
Among the Indo-Iranian languages, Sindhi reflects the non-aspirated voiced series unconditionally as implosives.Frederik Kortlandt, 'Glottalic Consonants in Sindhi and Proto-Indo-European', reprinted in Studies in Germanic, Indo-European, and Indo-Uralic, Amsterdam: Rodopi (2010), pp. 121-124. Counterarguments exist for his argument of no discernible substrate influence on the development of the specific Sindhi glottalization. See also Michael Witzel, "Substrate Languages in Old Indo-Aryan", Electronic Journal of Vedic Studies 1999 (http://www.ejvs.laurasianacademy.com/ejvs0501/0501ART.PDF ). Kortlandt also points out the distribution of voiced aspirates within Indo-Iranian: they are lacking from the Iranian languages and the Nuristani languages, two of the three accepted main branches of Indo-Iranian, and within the third, Indo-Aryan, also lacking from Kashmiri, which he suggests points to voiced aspirates being an innovation rather than a retention.
In Germanic, some Danish dialects have clusters of a glottal stop followed by a voiceless stop (vestjysk stød) which correspond with the Proto-Germanic voiceless stops, deriving from the allegedly-glottalized PIE series. Kortlandt also proposes word-final glottalization in English to be a retention and derives features such as preaspiration in Icelandic and Faroese and sporadically in Norwegian and certain instances of gemination in Swedish and High German from preglottalization as well.
In both Latin (Lachmann's law) and Balto-Slavic (Winter's law), vowels are lengthened before a "voiced" consonant. It is the same behaviour that vowels exhibit before Proto-Indo-European laryngeals, which are assumed to have included a glottal stop. It may be that the glottalic consonants were preglottalized or that they were ejectives that became preglottalized in Italic and Balto-Slavic before losing their glottalization and becoming voiced. It is very common in the world's languages for glottal stops to drop and lengthen preceding vowels. In Quileute, for example, the sequences , , and , as found in ak’a ~ a’k’a ~ āk’a, are allophones in free variation.
In Balto-Slavic, Kortlandt argues that the broken tone (i.e. glottalization) feature of Latvian and Žemaitian is not a later development, but a "direct reflection of PIE laryngeals and the glottalic feature".