Bayesian Time-Calibrated Phylogeny of Bhoyari (Pawari): BEAST2, PPC and ABC Evidence for Rajasthani Origin

 

Special issue of Pawari Shodh Patrika

Study U-1

Bayesian Time-Calibrated Phylogeny of Bhoyari (Pawari): BEAST2, PPC and ABC Evidence for Rajasthani Origin

Bayesian Phylogenetic Network, Posterior Predictive Checking,

and Approximate Bayesian Computation — A Complete Methodological Framework

ISBN:  978-620-9-62547-3

Author

Shivani Barange Pawar

Researcher – Bhoyari / Pawari Language Researcher, Folk Culture and Satpuda Regional Studies

Co-Editor, Writer & Contributor – Maa Tapti Shodh Sansthan, Multai, Betul & Pawari Shodh Patrika

Rajesh Barange Pawar

Independent Researcher | Bhoyari / Pawari Language Researcher | Pawar Bhoyar Community History | Rajasthan Malwa Satpuda Regional Studies

Founder & Director – Maa Tapti Shodh Sansthan, Multai, Betul | Chief Editor – Pawari Shodh Patrika

Pranay Chopde

Independent Researcher | Pawar Community History | Rajasthan Malwa Satpuda Regional Studies

Co-Founder– Maa Tapti Shodh Sansthan, Multai, Betul | Editor – Pawari Shodh Patrika

Published by

Maa Tapti Shodh Sansthan,

Multai, Betul, Madhya Pradesh

ABSTRACT

This study presents a Bayesian time-calibrated phylogenetic analysis of Satpuda Bhoyari's divergence within the Western Indo-Aryan macro-family, using three complementary computational historical linguistics frameworks: (1) BEAST2 Bayesian phylogenetic inference with a Relaxed Lognormal Clock and Binary Covarion substitution model; (2) Bayesian Posterior Predictive Checking (PPC) for model adequacy assessment; and (3) Approximate Bayesian Computation (ABC) for independent divergence time validation. The input data is a 200-item binary cognate matrix constructed from the authenticated Satpuda Bhoyari Lokgeet corpus and lexical dataset across six taxa (Bhoyari, Marwari, Mewadi, Rangdi, Malvi, Bundeli). Historical calibration priors are anchored to documented Western Indo-Aryan attestation dates.

BEAST2 analysis estimates Bhoyari divergence from Core Rajasthani at a posterior mean of 700 years before present (≈ 1325 CE), with a 95% Highest Posterior Density (HPD) interval of 575–825 BP (≈ 1200–1450 CE). Posterior node probability at the Proto-Bhoyari node is 0.92 — strong phylogenetic support. The relaxed clock identifies a three-phase trajectory: Proto-Bhoyari founding (~1300–1400 CE), Malwa contact phase (~1500–1700 CE), and Satpuda stabilization (~1700 CE onward). The Bayesian Skyline model shows a population proxy dip at founding, followed by gradual expansion during the Malwa phase and stabilization plateau post-1700 CE. PPC confirms adequate model fit: all three summary statistics (mean pairwise Hamming distance, homoplasy index, normalized tree height) fall within the 95% simulated range. ABC independently confirms the divergence estimate: posterior mean ≈ 680 BP, with Model A (~1300 CE split) receiving posterior probability 0.71 vs Model B (~1500 CE split, P=0.19) and Model C (~1700 CE split, P=0.10). SplitsTree5 phylogenetic network analysis reveals moderate reticulation (δ = 0.21) confirming Malwa contact influence without altering primary Rajasthani inheritance. Five independent computational methods converge on a single conclusion: Satpuda Bhoyari diverged from Core Rajasthani ~1300–1400 CE and was never derived from Malvi.

Satpuda Bhoyari (Pawari) exhibits lexical and phonological similarities with Malvi as a result of an extended Malwa contact phase lasting approximately 250–300 years during historical migration and settlement processes. However, these similarities are primarily superficial and arise from areal convergence rather than genetic affiliation.

Subsequent linguistic surveys and regional classifications, relying largely on such surface features, placed Bhoyari within the Malvi subgroup. Nevertheless, a deeper structural analysis—particularly of its phonology, morphology, and core grammatical system—reveals a significantly closer alignment with the Core Rajasthani linguistic group.

Therefore, Bhoyari is more appropriately understood as a southern extension of the Rajasthani dialect continuum, and its classification under Malvi represents a case of contact-induced misclassification rather than true linguistic derivation.

 

 

Keywords: BEAST2, Bayesian phylogenetics, time-calibrated tree, relaxed lognormal clock, Satpuda Bhoyari, Western Indo-Aryan, posterior predictive checking, approximate Bayesian computation, phylogenetic network, SplitsTree5, divergence time, historical linguistics, migration-chain model, Malwa contact, cognate matrix

1.1 Bhoyari/Pawari (Satpuda Zone): Identity and Scope

Bhoyari/Pawari (Satpuda Zone) is a sub-dialect of Malvi (as per linguistic researcher), belonging to the Western Indo-Aryan branch of the Indo-European language family. It is spoken exclusively by the Pawar / Bhoyar Pawar /Kshatriya Bhoyar Pawar community in the Satpuda region — specifically in Betul district, Chhindwara district, the Pandhurna region, and Wardha, in the states of Madhya Pradesh and Maharashtra. The dialect exhibits a rare sociolinguistic property: it is simultaneously geographically bounded and community-exclusive. No speakers of other castes or communities use Bhoyari/Pawari (Satpuda Zone) as a primary communicative code.

 

The Betul–Chhindwara–Pandhurna triangle is considered the prestige core of the dialect. The variety spoken in this triangle is regarded by community scholars and external observers alike as the most authentic and phonologically conservative form of Bhoyari/Pawari. The Wardha variety shows greater Marathi contact influence, while the Betul–Chhindwara core retains stronger Western Indo-Aryan structural features.

FIGURES — BAYESIAN PHYLOGENETIC ANALYSIS

The eight figures below provide complete visual coverage of the Study U-1 analytical results, from posterior density estimation through phylogenetic network visualization, skyline modeling, and ABC validation.

 

Figure 1.  Bayesian Posterior Density — Bhoyari Divergence Time BEAST2 posterior density (years before present). Green shading = core credible interval (650–750 BP). Blue shading = 95% HPD (575–825 BP ≈ 1200–1450 CE). Gold dashed = posterior mean 700 BP (~1325 CE). Upper axis shows corresponding CE dates. Unimodal distribution with slight right skew — typical of time-calibrated analyses. ESS > 250 confirms adequate sampling.

 

 

 

Figure 2.  Time-Calibrated Bayesian Phylogenetic Tree Maximum Clade Credibility tree from BEAST2 with posterior probabilities. X-axis = years before present (right = present). Proto-Bhoyari node (gold diamond) at ~1325 CE, PP=0.92. Dashed orange arrows = Malwa contact edges. Bundeli (red dotted) on separate Central IA branch. Three migration phases labeled: founding (~1325 CE), Malwa phase (~1500–1700 CE), Satpuda (~1700+).

 

 

 

Figure 3.  Bayesian Skyline Population Proxy — Migration Phase Modeling Normalized effective speaker population proxy (Ne) across Bhoyari history. Blue band = 95% credible interval. Three annotated phases: dip at Proto-Bhoyari founding (~1325 CE, small group); gradual expansion during Malwa contact (~1500–1700 CE); stable plateau post-1700 CE (Satpuda stabilization). Pattern consistent with founder effect → growth → stabilization.

 

 

 

Figure 4.  Bayesian Posterior Predictive Checks (PPC) — Three Summary Statistics Simulated distributions (blue histograms, n=1000) vs observed statistics (red lines). Left: Mean pairwise Hamming distance (obs=0.28, sim mean=0.27, range 0.22–0.31). Centre: Homoplasy index (obs=0.14, sim mean=0.13). Right: Normalized tree height (obs=0.72). All three observed values fall within 95% simulated range — model fit confirmed (✓).

 

Figure 5.  Approximate Bayesian Computation (ABC) — Divergence Model Comparison Left: ABC posterior density (blue, top 1% of 50,000 simulations) vs uniform prior (gray). ABC mean ≈ 680 BP (gold dashed), consistent with BEAST2 estimate (red dotted, 700 BP). Right: Model comparison — Model A (~1300 CE split) receives posterior probability 0.71; Models B and C receive 0.19 and 0.10. Two independent Bayesian frameworks agree.

 

 

Figure 6.  Bayesian Phylogenetic Network — SplitsTree5 NeighborNet Primary tree edges (solid colored lines) represent vertical inheritance. Dashed curved lines = contact/reticulation edges. Orange curve: Bhoyari ↔ Malvi (Malwa phase contact, δ=0.21). Purple curve: Bhoyari ↔ Rangdi (weak contact, δ=0.16). Marwari and Mewadi show low δ-scores (0.07–0.08), confirming tree-like inheritance. No reticulation edge with Bundeli — confirms separate Central IA lineage.

 

Figure 7.  Lexical Retention Decay Model — L(t) = e^(−λt) Left: Decay curves for all six varieties, calibrated λ values shown. Bhoyari (gold, λ=0.0011) retains ~46% of conservative core at 700 BP — matches observed corpus similarity of 40–55%. Right: Bhoyari λ posterior distribution. Prior (gray) = Normal(0.0011, 0.0003). Posterior (blue) narrowed by likelihood — ML estimate λ=0.0011 with 95% CI: 0.00095–0.00125 per year.

 

 

Figure 8.  Combined Model Validation Radar — Five Computational Methods Five-axis radar comparing performance of all analytical frameworks across: posterior probability, temporal accuracy, PPC model fit, ABC confirmation, and phylogenetic support. All four methods (green, teal, blue, purple) show consistently high scores across all five dimensions — convergent validation of the ~1300 CE divergence estimate.

 

The present linguistic and computational analysis not only establishes the phylogenetic position of Satpuda Bhoyari (Pawari), but also provides strong indirect historical evidence regarding the migration trajectory of the Bhoyar Pawar community.

 

The convergence of five independent Bayesian methods—BEAST2, Bayesian Skyline, Posterior Predictive Checking, Approximate Bayesian Computation, and SplitsTree5—confirms that Bhoyari diverged from the Core Rajasthani linguistic group around 1300–1400 CE. This linguistic divergence is not merely a structural phenomenon; it reflects a real historical separation of a speech community from the Rajasthani region.

 

Crucially, the presence of a prolonged Malwa contact phase (approximately 250–300 years), supported by measurable contact parameters (δ ≈ 0.21), lexical borrowing patterns, and demographic expansion signals, indicates that this migrating population did not move directly to the Satpuda region. Instead, it passed through and remained in the Malwa region for several generations, allowing significant but surface-level linguistic interaction with Malvi.

 

This sequence—Rajasthani origin → Malwa contact → Satpuda stabilization—is not an assumption but a model consistently supported by multiple independent datasets and analytical frameworks.

 

Therefore, the linguistic evidence aligns closely with and strongly supports the historical migration narrative of the Bhoyar Pawar community:

 

Rajasthani Origin (~1300 CE):

The divergence of Bhoyari from Core Rajasthani indicates that the ancestral Bhoyar Pawar population was originally part of the Rajasthani linguistic and cultural sphere.

 

Malwa Phase (~1400–1700 CE):

The statistically detectable Malwa contact phase demonstrates a prolonged settlement or interaction period in the Malwa region, during which linguistic convergence with Malvi occurred.

 

Satpuda Settlement (~1700 CE onwards):

The stabilization phase marks the final establishment of the community in the Satpuda region (Betul–Chhindwara zone), where Bhoyari developed into its present form.

 

Importantly, this linguistic reconstruction provides independent scientific validation of the community’s migration history—separate from oral traditions, genealogies, or historical texts. In other words, the language itself preserves the migration pathway.

 

Key Inference

 

The Bhoyari language functions as a linguistic record of migration: it proves that the Bhoyar Pawar community originated in Rajasthan, underwent a significant Malwa phase, and later settled in the Satpuda region.

 

Thus, this study goes beyond classification. It establishes that:

 

Bhoyari is structurally Rajasthani — confirming origin

Malvi influence is contact-based — confirming Malwa phase

Final linguistic stabilization in Satpuda — confirming settlement

 

Final Statement

 

Language here is not just a medium of communication—it is historical evidence.

And in the case of Bhoyari, it clearly encodes the Rajasthan → Malwa → Satpuda migration pathway of the Bhoyar Pawar community.

 

Five methods | One conclusion: Bhoyari ← Core Rajasthani ~1300 CE | NOT from Malvi | But Classified under Malvi | Satpuda stabilization ~1700 CE | PP = 0.92