V4

Antiquity of the Śivasūtras: Phylogenetic Constraints on the Vowel and Consonant Inventory

Abstract

The phonological distinctions in the vowel section of the Śivasūtras indicate articulatory capabilities distinct from those of anatomically modern humans. The consonant section indicates articulatory capacities that evolved only after the Homo–Pan split. This constrains the strata from which the Śivasūtras are composed to a period following the Homo–Pan split, yet preceding the extinction of non-sapiens Homo species.

Introduction

In Sanskrit grammar, all words are derived forms. Pāṇini’s Aṣṭādhyāyī comprises approximately 4,000 sūtras describing word derivation, reliant on a foundational list of phonemes (varṇas) known as the Māheśvara Sūtras or Śivasūtras. This phonemic inventory underpins Pāṇinian grammar (Aṣṭādhyāyī and Pāṇinīya Śikṣā) and is accepted as one of the earliest preserved linguistic artifacts. The present analysis examines the antiquity of the strata from which the Śivasūtras derive their phoneme list through phylogenetic dating, integrating articulatory phonetics, comparative primatology, and paleoanthropology.

Scope & Methodological Clarifications

The Śivasūtras have two sections: vowels (svaras) and consonants (vyañjanas).
Chronological bounds for the Śivasūtras are established by evaluating the following for each section:

1. Upper bound (terminus post quem): It is determined by the independent emergence of individual vowels (svaras) in the hominin lineage. Independent emergence of individual consonants is not attested in the hominin lineage before the Homo–Pan split, making that the terminus post quem for consonants. The composite inventory is feasible only after all consonants and vowels have been produced.

2. Lower bound (terminus ante quem): Inferred from (a) svaras present in the Śivasūtras but extinct in Homo sapiens per Pāṇinīya Śikṣā descriptions, and (b) svaras producible by Homo sapiens but absent in the Śivasūtras. It is not possible to determine a terminus ante quem for consonants beyond Homo sapiens, pending vocal tract reconstructions of earlier Homo species. The terminus ante quem for composite inventory is considered to be the terminus ante quem for vowels.

The vowel–consonant distinction is not a prerequisite for linguistic structure, as demonstrated by sign languages, which lack such a distinction yet exhibit fully developed and functional linguistic systems. However, when language is instantiated in the spoken–auditory modality, the vowel–consonant distinction becomes structurally central, organizing syllable structure, prosody, and temporal coordination within the vocal–auditory system. Accordingly, discussion of the Pāṇinīya Śikṣā and the Śivasūtras in this paper concerns the phonetic–phonological organization of speech rather than Sanskrit as a historical or grammatical language.
The analysis treats Pāṇinīya Śikṣā and the Śivasūtras articulatory categories as phonetic–phonological organization of the building blocks of speech and as internally consistent phonetic constraints, regardless of their historical authorship.

Phonetic Framework & Evolutionary Inference

Vowels

The vowel inventory in the Śivasūtras comprises three categories—quantal vowels (अ, इ, उ, ए, ओ), rhotic vowels (ऋ, ऌ), and derived vowels (ऐ, औ)—whose production requires specific articulatory and acoustic mechanisms traceable through hominin and primate evolution. Phylogenetic mapping of these “characters” (presence/absence of vowel types and combinatory abilities) constrains the upper bound for the vowel system’s compilation to the emergence of these capacities in the last common ancestor with relevant taxa.

Quantal vowels (अ, इ, उ, ए, ओ)

These five vowels exhibit stable formant patterns (F1/F2 dispersion-focalization) that minimize acoustic-perceptual confusion, as modeled by Stevens (1989) and quantified in human supralaryngeal vocal tract (SVT) simulations (Lieberman et al., 1969; Lieberman, 2012). Acoustic analyses of Guinea baboon (Papio papio) vocalizations reveal homologous vowel-like segments (VLSs) matching human [ɨ æ ɑ ɔ u], organized along two axes: horizontal (tongue advancement: [æ] ⇔ [u ɔ]) and vertical (tongue height: [ɑ] ⇔ [ɨ]) (Boë et al., 2017). Baboons achieve this despite a high larynx, using tongue musculature (genioglossus, hyoglossus, styloglossus) comparable to early hominins. This demonstrates that a stable, quantal-like acoustic substrate can be generated without the descended larynx characteristic of Homo sapiens. Such vowel-like segments (VLSs) are not vowels in the linguistic sense, but represent the biological-acoustic precursors from which the five primary human quantal vowels later evolved (Boë et al., 2017).

Accordingly, the last common ancestor with Cercopithecoidea (~25 Ma) establishes the maximal biologically imposed terminus post quem for the emergence of the quantal vowel substrate underlying the Śivasūtras’ vowel inventory. This bound applies to articulatory–acoustic capability alone and does not date the appearance of human-like vowels or symbolic phonological systems, both of which could arise only after this ability.

Derived vowels (ऐ, औ)

These arise from diphthongization (अ+इ → ऐ; आ+ओ → औ), requiring combinatorial sequencing. Comparative data show this ability predates quantal vowels: chimpanzees concatenate calls for context-specific meaning (Girard-Buttoz et al., 2025), Campbell’s monkeys form sequences (Ouattara et al., 2009), suricates vary alarm calls acoustically (Manser, 2001), and cetaceans/birds combine units (Payne & McVay, 1971). Combinatorial ability predates quantal vowels. The ability for ऐ and औ is constrained by availability of quantal vowels.

Rhotic vowels (ऋ, ऌ)

ऋ and ऌ are described in the Pāṇinīya Śikṣā and other Śikṣā texts as vowels. They are listed as distinct from contact (spṛśya) sounds, being characterized as a-spṛśya (non-contact) in their mode of articulation. In contemporary Sanskrit recitation, ऋ and ऌ are typically realized as syllabic rhotic and lateral consonants, conventionally transcribed as [r̩] and [l̩], respectively; these realizations involve articulatory contact and thus differ fundamentally from the non-contact (a-spṛśya) vowels described in the Śikṣā. In anatomically modern humans, the stable realization of ऋ and ऌ in this non-contact manner, as specified in the Śikṣā texts, does not appear to be supported. The question of how to articulate ऋ and ऌ is ancient. Apparently there are inconsistent instructions found in Pāṇinīya Śikṣā and Śaunakīyā Ṛkprātiśākhya–Śikṣā (Varma S., 1929, page 7.)

Rigveda-Prātiśākhya 1.41 states:
ऋकारऌकारावथ षष्ठ ऊष्मा जिह्वामूलीयाः प्रथमश्च वर्गः
The root of the tongue (jihvāmūla) is the articulator for ऋ, ऌ, ≍क (another sound defined in Sanskrit phonology that is not relevant for our discussion here) and the prathama varga (क ख ग घ and ङ).

Pāṇinīya Śikṣā Sūtra 17 states:
स्युर्मूर्धन्या ऋटुरषा दन्त्या ऌतुलसाः स्मृताः.
The place (स्थान) of articulation is the palate - roof of the oral cavity for ऋ, टु (ट ठ ड ढ ण) र and ष and teeth for ऌ, तु (त थ द ध न) ल and स.

The articulation by a radical (jihvāmūla) at Palate (mūrdha) is anatomically restricted in Homo sapiens. This limitation arises from the phylogenetic descent of the larynx, which resulted in a reorganized vocal tract where the posterior third of the tongue, the jihvāmūl, is sequestered within the oropharynx rather than the oral cavity proper. Consequently, the decoupled vertical and horizontal tongue masses in modern humans cannot achieve the specific palatal-radical configuration that was possible in ancestors with a near horizontal, intra-oral tongue.
Consequently, the phonological stratum reflected by the presence of ऋ and ऌ as vowels in the Śivasūtras is most plausibly associated with a pre-sapiens articulatory regime.

It is generally accepted that lowering of the larynx and tongue coincide with loss of laryngeal air sacs. The sound, especially vowels, produced by Homo species before the descent of the tongue, must have some effect from the laryngeal air sacs also.

Given the absence of laryngeal air sacs in Homo sapiens, any attempt to approximate open-tract, vowel-like vocalizations produced by co-existing Homo taxa with air sacs would necessarily involve articulatory substitution rather than direct replication. Among the available articulatory strategies in the sapiens vocal tract, rhotic and rhoticized articulations provide the most plausible means of introducing controlled vibratory and spectral complexity while preserving vocalic continuity. This does not imply homology between air-sac–mediated calls and human rhotics, but rather reflects a constrained approximation imposed by anatomical differences. In contemporary Sanskrit recitation, ऋ and ऌ are typically realized as syllabic rhotic and lateral consonants. This reflects above mentioned approximation imposed by anatomical differences.

Hyoid-based anatomical modelling suggests that laryngeal air sacs were no longer present in the Homo lineage by approximately 600-430 ka (de Boer, 2012 and Arsuaga, J. L., et al. 2014.)

This proposed phonation of ऋ ऌ as vowels produced with higher tongue position and air sacs is empirically testable: articulatory–acoustic modelling of vowel-like phonation incorporating simulated laryngeal air sacs could evaluate whether the resulting vibratory and spectral properties are best approximated, in a human vocal tract lacking air sacs, by rhotic or rhoticized articulations.

Absence of आ

Traditional Sanskrit grammar treats the dīrgha of अ as आ, with both represented by अ in the Śivasūtras; however, Aṣṭādhyāyī 8.4.68 distinguishes the dīrgha of अ from आ (Pāṇini, n.d.). The hypothesis that आ was omitted from the Śivasūtras purely for reasons of brevity is therefore not tenable. If brevity were the governing principle, the duplicate inclusion of ह would be difficult to explain. The presence of two occurrences of ह thus suggests that the absence of आ may reflect considerations other than mere economy of symbols in the structuring of the Śivasūtras.

Notably, आ appears in the Aṣṭādhyāyī but not in the Śivasūtras. This asymmetry is consistent with the possibility that the Śivasūtras predate the stable contrastive use of आ, whereas the Aṣṭādhyāyī postdates it. Accordingly, the absence of आ in the Śivasūtras is compatible with the hypothesis that at least some strata of this system derive from a period preceding anatomically modern human speech capacities.

Absence of 3 × 3 × 2 Grid

Sanskrit vowels exhibit 18 varieties: three tones (udātta, anudātta, svarita), three durations (hrasva, dīrgha, pluta), and nasal/non-nasal (3 × 3 × 2). These varieties are absent in the Śivasūtras. This may reflect brevity or absent fine motor control. Although present in Homo sapiens, their absence in the Śivasūtras is compatible with the pre-Homo sapiens inventory hypothesis.

Consonants

Two Types of ह

The Śivasūtras distinguish two ह forms, produced differently yet auditorily indistinguishable in Homo sapiens. This retention of perceptual distinction is compatible with the pre-Homo sapiens origin, with loss via anatomical or linguistic evolution.

Absence of ळ

ळ is absent in the Śivasūtras and dhātus but appears in later Vedic texts, accepted in sandhi but not word constituents. This suggests ळ emerged post-inventory fixation.

Other consonants

While Boë et al. (2017) demonstrate that the vocalic proto-system (vowels) is an ancient vertebrate inheritance traceable to ~25 Ma through acoustic analysis of vowel-like segments (VLSs), Demolin and Delvaux (2006) identify a distinct biological boundary for consonants. In their study of Bonobos (Pan paniscus), they conclude that no true consonants (or vowels) are observed, as these primates lack the sophisticated nervous control and the dynamic, non-uniform vocal tract shaping required to create the strictures (closures) defining consonantal production. Boë et al. (2017) do not dispute this finding for consonants and only present their finding with respect to vowel-like segments. The terminus post quem for the consonants section of the Śivasūtras is constrained at the Homo–Pan split at 5–7 Ma.
Consequently, the Śivasūtras preserve a phylogenetic record where the vowel section corresponds to an ancient, open-tract capability shared with Pan, while the consonant section marks the emergence of the obstructed-tract capabilities unique to the Hominini lineage post-divergence (5–7 Ma).

Conclusion

The Śivasūtras themselves may have been composed later, but the strata from which they take vowels and consonants are at least 430 ka old and 40 ka old respectively. Both vowels and consonants are younger than 7 Ma.
This conclusion is based on:

1. ऋ and ऌ as a-spṛśya svaras (lost in Homo sapiens)
2. आ absence (gained in Homo sapiens)
3. Absence of 18 svara varieties (gained in Homo sapiens)
4. Dual ह distinction (lost in Homo sapiens)
5. Consonants absent in Pan

The gap between the upper and lower bounds can be further reduced with additional work.

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