1. Direct comparison in early IE studies, informed by the Centum-Satem isogloss, yielded the reconstruction of three rows of dorsal consonants in Late Proto-Indo-European by Bezzenberger (1890), a theory which became classic after Brugmann (Grundriss, 1879) included it in its 2^nd Edition. The palatovelars *k^j, *g^j, and *g^jh were supposedly [k]- or [g]-like sounds which underwent a characteristic phonetic change in the satemized languages – three original “velar rows” had then become two in all Indo-European dialects attested.

NOTE. It is disputed whether Albanian shows remains of two or three series (cf. Ölberg 1976, Kortlandt 1980, Pänzer 1982), although the fact that only the worst known (and neither isolated nor remote) IE dialect could be the only one to show some remains of the oldest phonetic system is indeed very unlikely.

After that original belief, then, The centum group of languages merged the palatovelars *k^j, *g^j, and *g^jh with the plain velars *k, *g, and *g^h, while the satem group of languages merged the labiovelars *k^w, *g^w, and *g^wh with the plain velars *k,* g, and *g^h.

NOTE. Such hypothesis would then support an evolution [k^j] → [k] of Centum dialects before e and i, what is clearly against the general tendence of velars to move forward its articulation and palatalize in these environments.

2. The existence of the palatovelars as phonemes separate from the plain velars and labiovelars has been disputed. In most circumstances they appear to be allophones resulting from the neutralization of the other two series in particular phonetic circumstances. Their dialectal articulation was probably constrained, either to an especial phonetic environment (as Romance evolution of Latin [k] before [e] and [i]), either to the analogy of alternating phonetic forms. However, it is difficult to pinpoint exactly what the circumstances of the allophony are, although it is generally accepted that neutralization occurred after s and u, and often before r or a; also apparently  before m and n in some Baltic dialects

NOTE. The original allophonic distinction was disturbed when the labiovelars were merged with the plain velars. This produced a new phonemic distinction between palatal and plain velars, with an unpredictable alternation between palatal and plain in related forms of some roots (those from original plain velars) but not others (those from original labiovelars). Subsequent analogical processes generalized either the plain or palatal consonant in all forms of a particular root. Those roots where the plain consonant was generalized are those traditionally reconstructed as having “plain velars” in the parent language, in contrast to “palatovelars”.

Many PIE linguists still believe that all three series were distinct in Late Proto-Indo-European, although newest research show that the palatovelar series were a later phonetic development of certain Satem dialects, later extended to others; this belief was originally articuled by Antoine Meillet in 1893, and was followed by linguists like Hirt (1899, 1927), Lehmann (1952), Georgiev (1966), Bernabé (1971), Steensland (1973), Miller (1976), Allen (1978), Kortlandt (1980), Shields (1981), Adrados (1995), etc.

NOTE. There is, however, a minority who consider the labiovelars a secondary development from the pure velars, and reconstruct only velars and palatovelars (Kuryłowicz), already criticized by Bernabé, Steensland, Miller and Allen. Still less acceptance had the proposal to reconstruct only a labiovelar and a palatal series (Magnusson).

There is residual evidence of various sorts in the Satem languages of a former distinction between velar and labiovelar consonants:

·      In Sanskrit and Balto-Slavic, in some environments, resonant consonants (denoted by R) become iR after plain velars but uR after labiovelars.

·      In Armenian, some linguists assert that k^w is distinguishable from k before front vowels.

·      In Albanian, some linguists assert that k^w and g^w are distinguishable from k and g before front vowels.

NOTE. This evidence shows that the labiovelar series was distinct from the plain velar series in Late PIE, and cannot have been a secondary development in the Centum languages. However, it says nothing about the palatovelar vs. plain velar series. When this debate initially arose, the concept of a phoneme and its historical emergence was not clearly understood, however, and as a result it was often claimed (and sometimes still is claimed) that evidence of three-way velar distinction in the history of a particular IE language indicates that this distinction must be reconstructed for the parent language. This is theoretically unsound, as it overlooks the possibility of a secondary origin for a distinction.

3. The original (logical) trend to distinguish between series of “satemizable” dorsals, called ‘palatovelars’, and “non-satemizable” dorsals, the ‘pure velars’, was the easiest explanation found by neogrammarians, who apparently opened a different case for each irregularity they found. Such an initial answer should be considered erroneous today, at least as a starting-point to obtain a better explanation for this “phonological puzzle” (Bernabé).

NOTE. “Palatals” and Velars appear mostly in complementary distributions, what supports their explanation as allophones of the same phonemes. Meillet (1937) establishes the contexts in which there are only velars: before a, r, and after s, u, while Georgiev (1966) states that the palatalization of velars should have been produced before e, i, j, and before liquid or nasal or w + e, i, offering statistical data supporting his conclusions. The presence of palatalized velar before o is then produced because of analogy with roots in which (due to the apophonic alternance) the velar phoneme is found before e and o, so the alternance *k^je/*ko would be leveled as *k^je/*k^jo.

Arguments in favor of only two series of velars include:

  A) The plain velar series is statistically rarer than the other two, is entirely absent from affixes, and appears most often in certain phonological environments (described above).

B) Alternations between plain velars and palatals are common in a number of roots across different “Satem” languages, where the same root appears with a palatal in some languages but a plain velar in others. This is consistent with the analogical generalization of one or another consonant in an originally alternating paradigm, but difficult to explain otherwise:

·   *ak/ok-, sharp, cf.  Lith. akúotas, O.C.S. ostru, O.Ind. asrís, Arm. aseln, but Lith. asrùs.

·  *akmon-, stone, cf.  Lith. akmuõ, O.C.S. kamy, O.Ind. áśma, but Lith. âsmens.

·  *keu-, shine, cf. Lith. kiáune, Russ. kuna, O.Ind. Svas, Arm. sukh.

·   *b^hleg-, shine, cf. O.Ind.  bhárgas, Lith. balgans, O.C.S. blagu, but Ltv. blâzt.

·   *g^herd^h-, enclose, O.Ind. grhá, Av. gərəda, Lith. gardas, O.C.S. gradu, Lith. zardas, Ltv. zârdas.

·   *swekros, father-in-law, cf. O.Sla. svekry, O.Ind. śvaśru.

   B) The existence of different pairs (“satemized” and “not-satemized”) in the same language, as e.g.:

·   *selg-, throw, cf. O.Ind. sṛjáti, sargas

·   *kau/keu-, shout, cf. Lith. kaukti, O.C.S. kujati, Russ. sova (as Gk. kauax); O.Ind. kauti, suka-.

·   *kleu-, hear, Lith. klausýti, slove, O.C.S. slovo;  O.Ind. karnas, sruti,  srósati, śrnóti, sravas.

·   *leuk-, O.Ind. rokás, ruśant-.

NOTE. The old argument proposed by Brugmann (and later copied by many dictionaries) about “Centum loans” is not tenable today. For more on this, see Szemerény (1978), Mayrhofer (1952), Bernabé (1971).

  C)  Non-coincidence in periods and number of satemization stages;

·         Old Indian shows two stages,

1.       PIE *k → O.Ind. s, and

2.      PIE *k^we, *k^wi → O.Ind. ke, ki, & PIE *ske, *ski > O.Ind. c (cf. cim, candra, etc.).

·         In Slavic, however, three stages are found,

1.       PIE *k→s,

2.      PIE *k^we, *k^wi→č  (čto, čelobek), and

3.      PIE *k^woi→koi→ke gives ts (as Sla. tsená).

  D) In most attested languages which present aspirated as result of the so-called “palatals”, the palatalization of other phonemes is also attested (e.g. palatalization of labiovelars before e, i, etc.), what may indicate that there is an old trend to palatalize all possible sounds, of which the palatalization of velars is the oldest attested result.

  E) The existence of ‘Centum dialects’ in so-called Southern dialects, as Greek and some Paleo-Balkan dialects, and the  presence of Tocharian, a ‘Centum dialect’, in Central Asia, being probably a northern IE dialect.

NOTE. The traditional explanation of a three-way dorsal split requires that all Centum languages share a common innovation that eliminated the palatovelar series. Unlike for the Satem languages, however, there is no evidence of any areal connection among the Centum languages, and in fact there is evidence against such a connection -- the Centum languages are geographically noncontiguous. Furthermore, if such an areal innovation happened, we would expect to see some dialect differences in its implementation (cf. the above differences between Balto-Slavic and Indo-Iranian), and residual evidence of a distinct palatalized series (such evidence for a distinct labiovelar series does exist in the Satem languages; see below). In fact, however, neither type of evidence exists, suggesting that there was never a palatovelar series in the Centum languages.

4. It is generally believed that Satemization could have started as a late dialectal ‘wave’ (although not necessarily), which eventually affected almost all PIE dialectal groups. The origin is probably to be found in velars followed by e, i, even though alternating forms like *gen/gon caused natural analogycal corrections within each dialect, which obscures still more the original situation. Thus, non-satemized forms in so-called Satem languages are actually non-satemized remains of the original situation, just as Spanish has feliz and not *heliz, or fácil and not hácil, or French uses facile and nature, and not *fêle or *nûre as one should expect from its phonetic evolution. Some irregularities are indeed explained as borrowings from non-satemized dialects.

5. Those who support the model of the threefold distinction in PIE cite evidence from Albanian (Pedersen) and Armenian (Pisani) that they treated plain velars differently from the labiovelars in at least some circumstances, as well as the fact that Luwian apparently had distinct reflexes of all three series: *k^j > z (probably [ts]); *k > k; *k^w > ku (possibly still [k^w]) (Craig Melchert).

NOTE 1. Also, one of the most difficult problems which subsist in the interpretation of the satemization as a phonetic wave is that, even though in most cases the variation *k^j/k may be attributed either to a phonetic environment or to the analogy of alternating apophonic forms, there are some cases in which neither one nor the other may be applied. Compare for example *ok^jtō(u), eight, which presents k before an occlusive in a form which shows no change (to suppose a syncope of an older *ok^jitō, as does Szemerényi, is an explanation ad hoc). Other examples in which the palatalization cannot be explained by the next phoneme nor by analogy are *swekru-, husband’s mother, *akmōn, stone, *peku, cattle. Such (still) unexplained exceptions, however, are not sufficient to consider the existence of a third row of ‘later palatalized’ velars (Bernabé, Cheng & Wang), although there are still scholars who come back to the support of the three velar rows’ hypothesis (viz. Tischler 1990).

NOTE 2. Supporters of the palatovelars cite evidence from the Anatolian language Luwian, which supposedly attests a three-way velar distinction *k^j→z (probably [ts]); *k→k; *k^w→ku (probably [k^w]), defended by Melchert (1987). So, the strongest argument in favor of the traditional three-way system is that the the distinction supposedly derived from Luwian findings must be reconstructed for the parent language. However, the underlying evidence “hinges upon especially difficult or vague or otherwise dubious etymologies” (see Sihler 1995); and, even if those findings are supported by other evidence in the future, it is obvious that Luwian might also have been in contact with satemization trends of other (Late) PIE dialects, that it might have developed it’s own satemization trend, and that maybe the whole system was remade within the Anatolian branch.

6. A system of two gutturals, Velars and Labiovelars, is a linguistic anomaly, isolated in the PIE occlusive subsystem – there are no parallel oppositions b^w-b, p^w-p, t^w-t, d^w-d, etc. Only one feature, their pronunciation with an accompanying rounding of the lips, helps distinguish them from each other. Labiovelars turn velars before -u, and there are some neutralization positions which help identify labiovelars and velars; also, in some contexts (e.g. before -i, -e) velars tend to move forward its articulation and eventually palatalize. Both trends led eventually to Centum and Satem dialectalization.

A few sound-laws can be reconstructed, that may have been effective already in Late PIE dialects, by internal reconstruction.

·  Sievers’ Law (Edgerton’s Law, Lindeman’s option)

·  Hirt’s Law

·  Grassman’s Law

·  Bartholomae’s Law

Sievers’ Law in Indo-European linguistics accounts for the pronunciation of a consonant cluster with a glide before a vowel as it was affected by the phonetics of the preceding syllable. Specifically it refers to the alternation between *ij and *j, and possibly *uw and *u, in Indo-European languages. For instance, Proto-Indo-European *kor-jo-s became Gothic harjis “army”, but PIE *kerd^h-jo-s became Proto-Germanic *herdijas, Gothic hairdeis [hɛrdĩs] “shepherd”. It differs from an ablaut in that the alternation is context-sensitive: PIE *ij followed a heavy syllable (a syllable with a diphthong, a long vowel, or ending in more than one consonant), but *j would follow a light syllable (i.e. a short vowel followed by a single consonant). This was first noticed by Germanic philologist Eduard Sievers, and his aim was to account for certain phenomena in the Germanic languages. He originally only discussed *j in medial position. He also noted, almost as an aside, that something similar seemed to be going on in the earliest Sanskrit texts (thus in the Rigveda dāivya- “heavenly” actually had three syllables in scansion (dāivⁱya-) but say satya- “true” was scanned as written). After him, scholars would find similar alternations in Greek and Latin, and alternation between *uw and *u, though the evidence is poor for all of these. Through time, evidence was announced regarding similar alternations of syllabicity in the nasal and liquid semivowels, though the evidence is extremely poor for these, despite the fact that such alternations in the non-glide semivowels would have left permanent, indeed irreversible, traces.

The most ambitious extension of Sievers’ Law was proposed by Franklin Edgerton in a pair of articles in the journal Language in 1934 and 1943. He argued that not only was the syllabicity of prevocalic semivowels by context applicable to all six Indo-European semivowels, it was applicable in all positions in the word. Thus a form like *djēus, “sky” would have been pronounced thus only when it happened to follow a word ending with a short vowel. Everywhere else it would have had two syllables, *dijēus.

The evidence for alternation presented by Edgerton was of two sorts. He cited several hundred passages from the oldest Indic text, the Rigveda, which he claimed should be rescanned to reveal hitherto unnoticed expressions of the syllable structure called for by his theory. But most forms show no such direct expressions; for them, Edgerton noted sharply skewed distributions that he interpreted as evidence for a lost alternation between syllabic and nonsyllabic semivowels. Thus say śiras “head” (from *śṛros) has no monosyllabic partner *śras (from *śros), but Edgerton noted that it occurred 100% of the time in the environments where his theory called for the syllabification of the *r. Appealing to the “formulaic” nature of oral poetry, especially in tricky and demanding literary forms like sacred Vedic versification, he reasoned that this was direct evidence for the previous existence of an alternant *śras, on the assumption that when (for whatever reason) this *śras and other forms like it came to be shunned, the typical collocations in which they would have (correctly) occurred inevitably became obsolete pari passu with the loss of the form itself. And he was able to present a sizeable body of evidence in the form of these skewed distributions in both the 1934 and 1943 articles.

In 1965 Fredrik Otto Lindeman published an article proposing a significant modification of Edgerton’s theory. Disregarding Edgerton’s evidence (on the grounds that he was not prepared to judge the niceties of Rigvedic scansion) he took instead as the data to be analyzed the scansions in Grassmann’s Wörterbuch zum Rig-Veda. From these he concluded that Edgerton had been right, but only up to a point: the alternations he postulated did indeed apply to all semivowels; but in word-initial position, the alternation was limited to forms like *djēus/dijēus “sky”, as cited above—that is, words where the “short” form was monosyllabic.

Hirt’s law, named after Hermann Hirt who postulated it originally in 1895, is a Balto-Slavic sound law which states in its modern form that the inherited Proto-Indo-European stress would retract to non-ablauting pretonic vowel or a syllabic sonorant if it was followed by a consonantal (non-syllabic) laryngeal that closed the preceding syllable.

Compare:

·   PIE: *d^hūmós “smoke” (compare Sanskrit dhūmá and Ancient Greek thumós) → Lithuanian dū́mai, Latvian dũmi, Croatian/Serbian dȉm.

·   PIE *g^wrīw “neck; mane” (compare Sanskrit grīv) → Latvian grĩva, Croatian/Serbian grȉva.

·   PIE *