The Genomic Similarities with Linguistic Difference: A Study Among the Oraon and Munda Tribes of the Ranchi District,Jharkhand,India

Abstract

Aims: The present study was conducted on two tribal communities, the Oraon and Munda, inhabiting the Ranchi district of Jharkhand state, India. The study was designed to elucidate genetic similarity, if any, shared between these tribes as they belong to the common Proto-Australoid stock but bear different linguistic affiliations. For this, a total of 98 intravenous blood samples (48 Oraon and 50 Munda) were collected from unrelated individuals of either sex up to first cousins, with their prior informed written consent. The DNA was extracted and studied for a total of 20 autosomal markers, including 7 Alu Indels, 3 DRD2 TaqI sites, 3 β-globin sites, and 7 restriction site polymorphisms.Results: All the 20 studied molecular markers were found to be polymorphic in both the tribal population groups and showed similarities with respect to allele frequencies, with a low coefficient of gene differentiation (G_ST) value. Moreover, sharing and distribution patterns of haplotypes of the β-globin gene cluster suggest that the Oraon and Munda share a common ancestry. However, small differences between them with reference to the linkage disequilibrium (LD) pattern indicate that the Munda might have emerged as a result of admixture between Proto-Australoids and Austro-Asiatic-speaking Mongoloids as supported by the principal co-ordinate analysis, wherein the Munda are closely placed with the Dravidian-speaking Proto-Australoid tribes of India.Conclusion: A common genetic substratum (Proto-Australoid stock) of the Oraon and Munda was evident in the present study, although these tribes are distinct linguistically.

Introduction

India is the home of diverse communities belonging to various ethnic backgrounds. They are culturally divided into tribal and nontribal (caste) groups. Of these, the former exhibit more homogeneity because of their practice of strict endogamy. Both castes and tribes of India speak languages/dialects falling under four linguistic families, namely Indo-European, Dravidian, Austro-Asiatic, and Tibeto-Burman, which have region-specific distributions. Of these, Indo-European, Dravidian, and Tibeto-Burman languages are spoken by both tribal and nontribal communities, but Austro-Asiatic language is spoken exclusively by the tribal communities restricted to small pockets in the central and eastern parts of India. The Austro-Asiatic speakers can be branched into three groups, namely Mon Khmer, Khasi-Khmuic, and Mundari groups (Diffloth, 2005). It has been observed that the Mon Khmer (e.g., Nicobarese) and Khasi-Khmuic (e.g., Khasi) communities of India exclusively belong to the Mongoloid stock (Justin, 1990), forming a morphological continuity with the corresponding Mongoloid groups in East and Southeast Asia. However, a majority of Austro-Asiatic speakers along with Dravidian speakers of India have been ethnically classified as Proto-Australoid, which is proposed to form the original stock of the Indian mainland (Keith, 1936). The Dravidian linguistic family of the Indian subcontinent can be branched into three divisions, namely Southern Dravidian (e.g., Tamil, Malayalam, Kannada, Coorgi, Tulu, Toda, Kota, Telugu), Central Dravidian (e.g., Kui, Telugu, Gondi, Kolami, Parji, Koya, Kondh, Konda), and Northern Dravidian (e.g., Kurukh/Oraon, Malto, Brahui). Ethnically six racial elements are found in the Indian subcontinent, namely the Negrito, Proto-Australoid, Mongoloid, Mediterranean, Western brachycephals, and Nordic (Guha, 1935, 1944). Of these, the Negrito (Sharma, 1963) and Proto-Australoid (Keith, 1936) ethnic elements comprise the original/oldest gene pools of the mainland India. Although there has been a debate over tribe-caste continuum, eventually many of the studies have reached the consensus that tribal communities are the original inhabitants of the Indian mainland, and as the Austro-Asiatic linguistic family is specific to tribes, it is hypothesized by some to be the indigenous linguistic family (Gordon, 1958; Gadgil et al., 1998).

Human evolution has often been found at cross-roads in narrowing down to a specific phylogenetic pathway that is universally accepted from the two propositions, namely “out-of-Africa” (Cavalli-Sforza et al., 1988; Cavalli-Sforza, 1991; Vigilant et al., 1991; Wilson and Cann, 1992; Aiello, 1993) and “multiregional” (Thorne and Wolpoff, 1992; Frayer et al., 1993) theories. Keeping India in view, two major routes responsible for its initial peopling have been projected; first, from Africa, via Central Asia, to Northeast Asia, which then expanded toward Southeast Asia and to the islands beyond, that is, “the northern route” (Cavalli-Sforza et al., 1994), and the second from Africa through India to Southeast Asia and beyond, that is, “the southern route” (Nei and Ota, 1991; Chu et al., 1998; Su et al., 1999; Majumder, 2001; The HUGO Pan-Asian SNP Consortium, 2009). It has been proposed by Ballinger et al. (1992), Diamond (1997), and Gadgil et al. (1998) that the Austric language originated in China, from where it entered the Indian subcontinent through the northeast corridor and then diverged out its paths toward the islands. This is corroborated by the scattered distribution of the Austro-Asiatic speakers in India, particularly as pockets in the central and eastern regions.

The present study was designed to gain an insight into the peopling of India, specifically in relation to the several contending theories as to whether the Austro-Asiatic- or Dravidian-speaking tribal groups were the original inhabitants of the country.

For this, a total of 20 autosomal molecular markers were studied to provide a comprehensive view of genetic diversity and differentiation among Austro-Asiatic-speaking Munda and Dravidian-speaking Oraon inhabiting the eastern Indian state of Jharkhand.

Materials and Methods

The Oraon and Munda, the two tribal population groups of the Ranchi district (Jharkhand), were selected for the present study; the former belongs to Dravidian linguistic family, speaking the Kurukh dialect, whereas the latter belongs to the Austro-Asiatic linguistic family, speaking the Mundari dialect. For this work, 5 mL intravenous blood sample was drawn by a trained medical technician from each of a total of 98 unrelated individuals (40 Oraon and 50 Munda) up to first cousins of either sex, with their prior informed written consent. The fieldwork was conducted in 20 villages from three blocks, namely Kanke, Mandar, and Ratu of the district (Fig. 1). As the study involved blood collection from humans, prior approval for conducting the study was obtained from the Ethical Committee of the Department of Anthropology, University of Delhi, Delhi.

FIG. 1.

Map of India showing the geographical location of Ranchi district, Jharkhand.

Laboratory analysis

Genomic DNA was isolated from the collected blood samples using the salting-out method of Miller et al. (1988). Each DNA sample was typed for a total of 20 polymorphic autosomal sites, 7 Alu indel markers (PV92, FXIIIB, D1, APO, ACE, CD4, PLAT), 3 TaqI sites (A, B, D) of Dopamine D2 Receptor gene (DRD2), 3 sites of β-globin gene cluster [HBψβ (HB7), HB3′ψβ (HB8), HB5'β (HB9)], and 7 restriction site polymorphisms (ESR, LPL, T2, NAT, PSCR, ALAD, ADH2). The protocols used for Alu indel markers have been described by Stoneking et al. (1997), Majumder et al. (1999), and Watkins et al. (2001). The chromosomal locations, primer sequences, and polymerase chain reaction conditions for each restriction fragment length polymorphism studied are given in the Genome Base and listed by the Eccles Institute of Human Genetics (www.genetics.utah.edu/∼swatkins/pub/RSP_links.html). The protocols for DRD2 and β-globin markers are as mentioned by Jorde et al. (1995), Kidd et al. (1998), Majumdar et al. (1999), and Mukherjee et al. (2000). All the restriction site polymorphism markers were digested using 5 U of the appropriate restriction enzyme. The final product was then subjected to electrophoresis at 100 V on agarose gel. The results were noted and documented using a gel documentation system.

Statistical analysis

The allele frequencies of the selected markers were calculated by the gene counting method. The statistical software POPGENE version 1.32 (Yeh et al., 1999) was used to obtain heterozygosity and average heterozygosity estimates along with their standard deviations. Evaluation of the Hardy-Weinberg equilibrium was done by means of the chi-square (χ²) goodness-of-fit test and its statistical significance was considered at 5% level. Genetic differentiation was computed using DISPAN (Ota, 1993). The maximum likelihood estimates of haplotype frequencies were calculated from the multisite marker typing data using HAPLOPOP (Majumdar and Majumder, 1999). The coefficient of standardized pairwise linkage disequilibrium D′ (Lewontin, 1964) and the corresponding χ² values were calculated with the LD software (Hill, 1974). Principal co-ordinate (PCO) analysis was performed using data on 17 common markers (PV92, FXIIIB, D1, APO, ACE, PLAT, 3 beta globin sites [HB7, HB8, HB9], 3 DRD2 TaqI sites [A, B, D], ESR, LPL, T2, NAT, PSCR). The software PCO version 2 (www.cse.naro.affrc.go.jp/iwatah/others/pco/index.html) was used to graphically represent the extent of genetic affinities among the population groups under study and those of the other reported Indian population groups (Chakrabarti et al., 2002; Vishwanathan et al., 2003; Saraswathy et al., 2008, 2009a). The relative amount of gene flow experienced by the Indian populations was estimated using the island model of Harpending and Ward (1982) and data from other populations on 17 common markers as mentioned before (Chakrabarti et al., 2002; Vishwanathan et al., 2003; Saraswathy et al., 2008, 2009a).

Results

All the 20 autosomal markers were found to be polymorphic in both the tribal population groups. Of these, markers each in the Oraon (FXIIIB, D1, CD4, PLAT, DRD2 TaqI D, HB9, ALAD) and Munda (FXIIIB, ACE, CD4, DRD2 TaqI A, HB7, T2, ADH2) exhibited a significant deviation from the Hardy-Weinberg equilibrium (Table 1). The frequencies of the autosomal markers have been tabulated along with their standard errors, which do not exceed the value of±2.0, indicating that the present tribes were in genetic equilibrium and deviations observed were just by chance (Table 1). In general, similar heterozygosity values were found at different loci for both the Oraon and Munda, albeit the latter tribe was found to have a relatively higher average heterozygosity (0.427) compared with the former tribe (0.407).

Table 1.

Distribution of Allele Frequencies and Heterozygosity Among the Oraon and Munda of Ranchi District, Jharkhand

	Population groups
	Oraon				Munda
Marker	Allele frequency	Heterozygosity	χ²	p-Value	Allele frequency	Heterozygosity	χ²	p-Value
PV92	0.500±0.051	0.5	0	1	0.750±0.043	0.375	0.72	0.396144
FXIIIB	0.552±0.051	0.4946	18.504	0.000017^a	0.670±0.047	0.4422	23.352	0.000001^a
D1	0.156±0.037	0.2637	9.587	0.001968^a	0.286±0.045	0.4082	0.49	0.483942
APO	0.844±0.037	0.2637	0.035	0.850726	0.816±0.039	0.2999	0.387	0.533816
ACE	0.594±0.050	0.4824	0.304	0.581219	0.602±0.049	0.4792	6.391	0.011490^a
CD4	0.022±0.015	0.0425	46	0.000000^a	0.052±0.022	0.0987	29.882	0.000000^a
PLAT	0.542±0.051	0.4965	8.171	0.004270^a	0.490±0.049	0.4998	2.876	0.089887
DRD2 TaqIA	0.739±0.045	0.4297	0.442	0.50611	0.663±0.047	0.4867	5.174	0.022952^a
DRD2 TaqIB	0.562±0.051	0.4633	0.485	0.486139	0.571±0.049	0.4608	1.361	0.243325
DRD2 TaqID	0.427±0.050	0.3047	6.27	0.012300^a	0.540±0.050	0.4398	3.673	0.055308
HB7 (HBψβ)	0.845±0.037	0.5	0	0.994395	0.847±0.036	0.4648	6.558	0.010462^a
HB8 (HB3′ψβ)	0.406±0.042	0.4824	1.546	0.213654	0.418±0.049	0.4867	0.857	0.354675
HB9 (HB5′β)	0.500±0.051	0.2616	5.333	0.020943^a	0.367±0.048	0.2593	0.728	0.393633
ESR	0.635±0.049	0.3856	2.199	0.138065	0.640±0.048	0.4467	0.825	0.363642
LPL	0.812±0.040	0.4922	0.424	0.514826	0.673±0.047	0.4898	1.33	0.248723
T2	0.312±0.047	0.4894	3.26	0.071	0.418±0.049	0.4967	4.409	0.035775^a
NAT	0.771±0.043	0.3533	1.544	0.213976	0.714±0.045	0.4082	1.96	0.161497
PSCR	0.326±0.048	0.4395	0.358	0.549853	0.357±0.048	0.4592	1.96	0.161497
ALAD	0.269±0.045	0.3935	5.294	0.021425^a	0.272±0.044	0.3958	1.083	0.298031
ADH2	0.256±0.044	0.381	1.155	0.282498	0.617±0.049	0.4726	14.208	0.000165^a
Average heterozygosity	0.407				0.427

p-Value is indicative of the significant deviation from Hardy-Weinberg equilibrium.

To study genic differentiation, G_ST values were calculated, which show great heterogeneity over 20 marker loci. The average G_ST value obtained (0.01805) was low, which may be attributed to little genetic differentiation between the Oraon and Munda tribes (Table 2).

Table 2.

Distribution of Genetic Differentiation Between the Oraon and Munda of Ranchi District, Jharkhand

Marker	G_ST
PV92	0.066667
FXIIIB	0.014646
D1	0.024541
APO	0.001389
ACE	0.000067
CD4	0.006315
PLAT	0.002707
DRD2 TaqIA	0.01212
DRD2 TaqIB	0.000027
DRD2 TaqID	0.025264
HB7 (HBψβ)	0.018008
HB8 (HB3′ψβ)	0.000149
HB9 (HB5′β)	0.000008
ESR	0.006889
LPL	0.000082
T2	0.013009
NAT	0.004248
PSCR	0.001068
ALAD	0.000011
ADH2	0.132457
All markers	0.018058

Of the eight possible β-globin haplotypes (prepared in the sequence HB9-Hb8-Hb7, each site having two alleles, with “+” allele indicating presence of site and “−” allele indicating absence of site), six were found among the Oraon and seven among the Munda (Table 3). The +−− haplotype was the most preponderant among both the Munda (48.2%) and Oraon (38.6%). For three of the haplotypes, +++, ++−, and +−+, the Oraon have nearly the same percentage of distribution, that is, 15.5%, 15.0%, and 15.4%, respectively. The standardized pairwise linkage disequilibrium (D′) values measured for the three sites, namely HB7, HB8, and HB9, of the beta globin gene (Table 4) were found to be low, that is, below both the tribal population groups.

Table 3.

Haplotype Distribution of Three Beta-Globin Sites Among the Oraon and Munda of Ranchi District, Jharkhand

	Oraon		Munda
Possible haplotypes	Haplotypic frequencies	Percentile	Haplotypic frequencies	Percentile
+++	0.155	81	0.152	81
++−	0.150	56	0.130	69
+−+	0.154	69	0.090	44
+−−	0.386	94	0.482	88
−++	0.111	44	0.113	56
−+−	0.000	13	0.022	31
−−+	0.044	19	0.000	6
−−−	0.000	13	0.011	19

Haplotypes were prepared with beta-globin sites in the order HB9-HB8-HB7.

Each site has two alleles—“+” allele indicating presence of site and “−” allele indicating absence of site.

Table 4.

Pairwise Linkage Disequilibrium Values of β-Globin Locus

Population	HB9-HB8	HB8-HB7	HB7-HB9
Oraon
D′ value	0.042271	0.065640	−0.09612
χ²	2.36.371	3.429581	0.118605
p-Value	>0.05	>0.05	>0.05
Munda
D′ value	−0.072278^a	0.118427^a	0.059483^a
χ²	8.282304	12.152090	5.960759
p-Value	<0.01	<0.01	<0.02

Statistical significance at 5% level.

The PCO scatterplot (Fig. 2) shows both the Oraon and Munda in relatively close proximity, but the former tribe tends to form a cluster with the Dravidian populations of Andhra Pradesh and Nilgiri Hills (Tamil Nadu). The plot also shows that the populations from Northeast India form a separate cluster, although the Meitei of Manipur are found to be closer to the bigger cluster comprising the Oraon, Munda, and populations from Andhra Pradesh and Nilgiri Hills. Both the Mizo and Toda can be found at the opposite ends of the plot, none of them being close to any of the two major clusters.

FIG. 2.

Principal co-ordinate scatterplot based upon 17 autosomal markers exhibiting genetic affinities among the Oraon and Munda and another 16 population groups from South India and Northeast India.

Discussion

The Oraon and Munda tribes show similarity with respect to allele frequencies of the molecular markers studied with a very low G_ST value. Moreover, sharing and distribution patterns of haplotypes of β-globin gene cluster and also of DRD2 locus (Sachdeva et al., 2010) suggest that they share a common genetic ancestry. The difference found between them is only in LD patterns at both β-globin and DRD2 loci—the Oraon show statistically nonsignificant low LD with respect to three β-globin sites and three DRD2 TaqI sites (Sachdeva et al., 2010), whereas the Munda exhibit a statistically significant LD at all these sites. According to Sawyer et al. (2005), subpopulations of the same geographical region are expected to show similar LD patterns. However, the observed differences between the present two tribes can be conveniently attributed to the admixture scenario among the Munda (Van Driem, 2006). This tribe with slight Mongoloid features and belonging to the Austro-Asiatic linguistic group is thus an example of the fact that languages (cultural attributes) travel faster with greater intensity when compared to the genes.

It has been postulated that India has acted as a major corridor for human migration from Africa to Southeast Asia through the northeast border as the major land route (The HUGO Pan-Asian SNP Consortium, 2009). However, a contrary view was proposed by Cordaux et al. (2004), Thangaraj et al. (2005), Macaulay et al. (2005), and Saraswathy et al. (2009a) that the northeastern border was more of a barrier than corridor, which allowed inflow of people from Southeast Asia but not the back migration. This finding is basically hinged on the genetic discontinuity in Northeastern Mongoloid and other non-Mongoloid Indian population groups (Saraswathy et al., 2009b). The northeastern land route seems not to be a very convenient and feasible one, with the Himalayas spanning the major portion of the route save the Manipur-Myanmar border. Moreover, the movement of people from South and Central India toward the northeastern border also had geographical (hills) and climatic (cold climate) limitations. Thus, the present data indicate that the Mundari-speaking Munda, with very small traces of Mongoloid features, was found to be genetically similar to the Dravidian-speaking Oraon. This suggests that Austro-Asiatic-speaking people entering India through the northeast border might have substantially contributed their language to certain groups of people in the Indian subcontinent, as is evident by the distribution of Austro-Asiatic speakers in small pockets of the central and eastern parts of India. In contrast, their genetic contribution seems to be limited as seen in the case of the Munda in the present study.

Interestingly, the Austro-Asiatic-speaking Khasi tribe of Meghalaya lives closer to the northeastern border of India and exhibits exclusively Mongoloid features. This could have been possible only when Austro-Asiatic speakers from Central China entered India through northeast border and maintained identity as Khasi or else they substantially contributed both language and genes to already existing people, resulting in the Khasi tribe. Thus, the Austro-Asiatic language, spoken widely in Southeast Asian countries by the people with Mongoloid features, is expected to have reached India later. On the contrary, an ethnic element, that is, the Proto-Australoid, is not only found in the majority of primitive and advanced tribal groups but also among some of the high-caste groups of India, indicating a basal genetic substratum of Indian subcontinent as also proposed by Saraswathy et al. (2010).

The Oraon, with typical Proto-Australoid features and speaking a Dravidian tongue, are expected to be closer to the Dravidian speakers of South India. The Munda present a very interesting situation that despite belonging to a different linguistic group, they are placed in between Dravidian and Austro-Asiatic speakers but are relatively closer to the Oraon, indicating their genetic proximity with Proto-Australoid Dravidian-speaking tribes of India. Another Austro-Asiatic speaking tribe, the Ho, is found to be closer to Dravidian populations as against Austro-Asiatic or Tibeto-Burman speakers. It is also evident that the Tibeto-Burman-speaking Meitei group of Manipur (Northeast India), with mongoloid features, also lies in genetic proximity of the major cluster as they inherit the Proto-Australoid stock (Saraswathy et al., 2009a). In contrast to previous studies that support the idea that linguistic affiliations coincide with genetic similarities (Barbujani and Sokal, 1990; Barbujani, 1991; Dupanloup de Ceuninck et al., 2000; Thangaraj et al., 2005; Majumder, 2010), the PCO analysis (Fig. 2) in the present study reveals that the Tibeto-Burman-speaking Meitei tribe, the Austro-Asiatic-speaking Munda tribe, and Dravidian-speaking tribes form a major cluster, suggesting that geographic placement and ethnicity bear greater impact on genes compared to language. In the centroid analysis, all Dravidian-speaking populations along with Austro-Asiatic-speaking Munda and Indo-European-speaking Rana Tharu indicate gene flow among them with higher heterozygosity (Fig. 3). This is suggestive of larger effective sizes of these populations in India. This conforms well with the already reported fact that South Indian populations have diversified sources of gene flow (Saraswathy et al., 2008).

FIG. 3.

Centroid analysis using common 17 markers on the studied populations with other Indian populations.

Isolated populations showing lower heterozygosity values include the Austro-Asiatic-speaking Ho tribe, Tibeto-Burman-speaking Meitei, Paite, Thadou, Kom, Mizo, and Dravidian-speaking Kota and Toda tribes. From this, one can infer that isolation with respect to geography, language, and culture brought out homogeneity among populations, leading to distinctive gene pools. Thus, peopling of India may be attributed not only to autochthonous origin, and as a result of migration and admixture, but also to social rules such as strict endogamy prevailing in certain communities and areas.

Conclusion

Linguistically distinct Oraon and Munda of the Ranchi district are found to be genetically similar with respect to 20 autosomal genetic markers. Small differences between them with reference to the LD pattern indicate that the Munda might have emerged as a result of the admixture between Proto-Australoids and Austro-Asiatic-speaking Mongoloids. This is also evident from PCO analysis, wherein the Munda were closely placed with the Dravidian-speaking Proto-Australoid tribes of India. The present study also indicates a longer history of the Oraon in the region when compared with the Munda. Thus, a common genetic substratum (i.e., Proto-Australoid stock) of the two tribes is conspicuous in the present study for 20 autosomal loci.

Footnotes

Acknowledgments

The authors are thankful to the University Grants Commission for providing the financial support to conduct the present study. The authors are also grateful to the Department of Anthropology, University of Delhi, for providing the infrastructure to carry out the study.

Disclosure Statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the manuscript.

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