Inner–Outer hypothesis

The general structure of the hypothesis is that there were two groups of Indo-Aryan speakers who migrated into the subcontinent through differing routes and spoke different dialects of Old Indo-Aryan. This is meant to explain commonalities between the Outer languages (specifically the Eastern Indo-Aryan languages and Sindhi, Gujarati, Marathi, and associated smaller lects) that are not found in the Madhyadeśa region.

Hoernlé's original formulation in 1880 of the Inner–Outer hypothesis was an initial Māgadhan invasion (at this time, the migration of Indo-Aryans was considered to be an invasion, a theory now largely refuted) into the Indo-Gangetic plain, followed by a second Śaurasenī invasion that pushed the earlier Aryans outwards into the south, east, and west. He further thought that Pashto and the Nuristani languages belonged to the Outer Māgadhan group.[10] Grierson calls this the wedge theory and does not accept it in its entirety, but agrees in the political result, adding that there is textual evidence of hostility between the two groups in e.g. Mahābhārata, in which the Indus Aryans are called mleccha "~barbarians".[11]

The most recent iteration of the theory is by Franklin Southworth.[12] His hypothesis states that at the time of the Rigveda, the Indo-Aryans resided in the upper Indus valley and had largely lost contact with Iranian speakers. Some dialectal variation was already present at this stage but the Inner and Outer groups had not split. The Inner Indo-Aryan speakers, associated with the post-Rigvedic textual tradition of Hinduism, then migrated directly into the Madhyadeśa, while the Outer IA speakers took a path south into Sindh, then east to the Deccan and Malwa, and finally to the east into Bengal by the time of Aśoka. The Inner and Outer languages regrouped around Awadh, leading to dialect mixture in that area (reflected in Grierson's classification of those languages as intermediate between Inner and Outer IA).

The basic agreed-upon part of the hypothesis by its proponents from the very beginning is that modern Marathi–Konkani and Bengali–Assamese–Odia share more features with each other than with the other Indo-Aryan languages. Thus, they form the backbone of the Outer language family. Grouping of the transitional language is more thorny; most formulations of the theory add Gujarati, Sindhi, and the Bihari languages to the Outer family, while there is more contention (and lack of data) in categorising Western Punjabi, Dardic, Sinhala–Dhivehi, and Pahari. Eastern Hindi is thought to be transitional between Inner and Outer.

Below are the groupings proposed by proponents of the hypothesis.

Zoller (2016, p. 79) noted that the big issue in grouping Indo-Aryan languages firmly into either group is the presence of dialect stratification; large koiné languages such as Hindi and Bengali, or the older Dramatic Prakrits, engaged in dialect levelling that obscured their belonging to either group, and local village dialects may have a very different composition of features that are unfortunately not historically preserved. He takes a more nebulous view of the grouping into Inner and Outer:

"[A]n individual language is either more Outer and less Inner Language or vice versa, depending on the amount of typical Outer Language features characterizing that individual language."

For him, Nuristani, Dardic, and West Pahari are among the most Outer languages, transitional into Old Iranian historically. Within branches, Zoller claims Assamese and Odia have more Outer features than Bengali, and Konkani has more than Marathi.

The evidence underlying the hypothesis is shared innovations between the Outer languages. Zoller narrows the proof for the hypothesis down to two criteria: the Outer languages must show some Proto-Indo-European feature that is not reflected in Vedic Sanskrit (thus proving that they descend from a different OIA dialect) and also they must show stronger substrate influence from Dravidian and Munda (thus proving that they represent an earlier migration).[13]

Grierson's linguistic evidence was almost entirely refuted by Chatterji; some of the points that were discarded in modern formulations of the hypothesis are the preservation of final short vowels in semi-tatsamas (e.g. Bihari mūratⁱ "idol"), the movement of the Outer languages towards a more synthetic paradigm, and various innovative developments of the sibilants (s > ś, h, x).[3] However, Grierson's primary evidence of the past in -l- has remained the most important piece of linguistic evidence in all forms of the hypothesis.

Southworth, based on the earlier work by Grierson, adds historical correlates of these features in the Ashokan Prakrit inscriptions (the northwestern inscriptions reflect a different dialect from the eastern and western ones) and potentially as early as the dialectal variation of Vedic Sanskrit.[4] He also tightens the diagnostic evidence of the grouping, focusing only on exclusively shared innovations as a basis for genetic classification of languages. His evidence is:

• Past forms in -l-: This form is found in the Outer IA languages to mark the past indicative and/or the past/perfective participle. Evidence suggests that it was suffixed (rather than replacing) to the original past form in Sanskrit with -ta, e.g.: OIA ga-ta "gone" > MIA *ga-y-alla > Marathi gelā. The morpheme -alla/ulla/illa- was widespread in Middle Indo-Aryan as a general adjectival suffix (e.g. Hindi ag-lā "next" < MIA agg-alla). Southworth's examination of textual evidence finds that the past in -l- is earliest found in Marathi, with variable attestation in the Eastern IA languages, suggesting a diffusion of the change from west to east rather than a fully shared innovation. Nevertheless, this is the strongest example of a shared Outer feature.
• Verb forms in -(i)tavya: This was generalised into a gerund, an infinitive, and the future tense from its necessitative use in late OIA, while the inner languages have a gerund and infinitive < OIA -anīya and assorted future forms.
• Phonological change r̥ > a: The vocalic rhotic r̥ was changing into a non-rhotic vowel by the OIA stage, as evidenced by changes such as Proto-Indo-Iranian r̥H > OIA īr/ūr and variant forms in Vedic. There is a split by the time of Ashokan Prakrit of the reflex i in the Northwest and a elsewhere (i.e. in the East and West, corresponding to Outer IA). A modern example is OIA mr̥ttikā "earth" > Punjabi miṭṭī but Bengali māṭī, Marathi mātī.
• Loss of length contrast in i/u: The length distinction from OIA i ~ ī and u ~ ū is lost in Outer languages, becoming positionally determined.
• Word-initial accent: The Inner languages have a weight-based stress accent while the Outer language have a default initial-syllable accent, reflected by vowel lengthening in that position, e.g. OIA karpāsa > Hindi kapās, but Marathi kāpus, Bengali kāpās.
• Phonological change l > n: This change is largely confined to Maithili and broadly Eastern IA, but Southworth suggests cases of lexical diffusion from east to west bypassing the Madhyadeśa languages, and thus linguistic links between the two that persisted quite late.

Zoller (2016) further claimed that only the first feature is necessary to judge an Outer subfamily, by linking it to the Indo-European adjectival suffix *-ulo/elo/ilo- and *-ah₂-lo-, *-eh₁-lo- that is not preserved as broadly in Vedic Sanskrit (besides individual lexical items such as bahulá "thick"). He notes similar developments of a gerund in Tocharian and participle forms in Slavic. The gemination in the MIA forms is explained as a reflex of PIE *-Vl-yo as in Tocharian. He also suggested that the d ~ ḍ alternation and c, j > ċ, (d)z (in Nuristani, Dardic, and Pahari) are relevant features to the hypothesis but left their investigation for future work.

For Zoller, further linguistic evidence lied in substrate influence from Munda, Tibeto-Burman, and Dravidian found in the Outer languages. He postulates that north India was largely Munda-speaking, citing Munda substrata in the West Himalayish languages. He goes on to cite parallels between syllable structure in West Pahari and Munda (the sesquisyllabic structure), convergence of ideophones in Indo-Aryan with Munda, consonant fluctuations in Outer IA deśī vocabulary and Munda, and lexical parallels between Munda, Tibeto-Burman, Burushaski, and Outer IA.[14]

There is a historical split between the Indo-Aryans of the Madhyadeśa region (focused on modern-day western Uttar Pradesh, and more generally the Indo-Gangetic plain) and Indo-Aryans of other regions. Religious texts divide the lands of India into ārya "Aryan" and mleccha "barbarian", the latter including all of the non-Madhyadeśa regions even after their Aryanisation and adoption of Indo-Aryan languages. Grammarians such as Patañjali relate that the dialect of the Asuras (demons) had the change r > l, a distinctly eastern Indo-Aryan change. Listings such as the Pañca-draviḍa group Gujarat and Maharashtra with the non-Indo-Aryan Deccan.[15]

Following work on the structural typology of Indo-Aryan, Munda, and Dravidian, Peterson (2017) proposed an East–West split in Indo-Aryan, with Eastern Indo-Aryan and Bihari undergoing historical convergence with Munda due to a long period of contact. Some of the Eastern features he put forth supporting this proposal are lack of ergativity, loss of gender marking, numeral classifiers, lack of oblique nominal stems, and lack of attributive agreement.[17] He does not explicitly reject the Inner–Outer hypothesis in the text, but his grouping puts Marathi–Konkani as closer to the Central IA languages (e.g. Hindi) than to Eastern IA, so it is incompatible with the Inner–Outer hypothesis.

• Cardona, George; Jain, Dhanesh (2003), "General Introduction", in Cardona, George; Jain, Dhanesh (eds.), The Indo-Aryan Languages, Routledge, ISBN 978-0-415-77294-5
• Cathcart, Chundra A. (2020). "A probabilistic assessment of the Indo-Aryan Inner–Outer Hypothesis". Journal of Historical Linguistics. 10 (1): 42–86. arXiv:1912.01957. doi:10.1075/jhl.18038.cat. S2CID 208617417.
• Chatterji, Suniti Kumar (1926). The Origin and Development of the Bengali Language. Calcutta: Calcutta University Press.
• Grierson, George (1920). "Indo-Aryan Vernaculars (Continued)". Bulletin of the School of Oriental Studies, University of London. 1 (3): 51–85. doi:10.1017/S0041977X00087152.
• Grierson, George A. (1927). Linguistic Survey of India. Vol. I, Part 1, Introductory. Calcutta: Office of the Superintendent of Government Printing, India.
• Hoernlé, Rudolf (1880). A Comparative Grammar of the Gaudian Languages. Trübner & Company.
• Masica, Colin (1991), The Indo-Aryan Languages, Cambridge: Cambridge University Press, ISBN 978-0-521-29944-2
• Peterson, John (2017). "Fitting the pieces together - Towards a linguistic prehistory of eastern-central South Asia (and beyond)". Journal of South Asian Languages and Linguistics. 4 (2): 211–257. doi:10.1515/jsall-2017-0008. S2CID 135081106. ProQuest 1945799940.
• Southworth, Franklin C. (2005), Linguistic archaeology of South Asia, Routledge, ISBN 0-415-33323-7
• Stroński, Krzysztof; Verbeke, Saartje (2020). "Shaping modern Indo-Aryan isoglosses". Poznań Studies in Contemporary Linguistics. 56 (3): 529–552. doi:10.1515/psicl-2020-0017. S2CID 222005280. ProQuest 2444064992.
• Zoller, Claus Peter (2016). "Outer and Inner Indo-Aryan, and northern India as an ancient linguistic area". Acta Orientalia. 77: 71–132.