Genetic History of India

Raj Vedam of Indian History Awareness & Research (IHAR) highlights the mainstream narrative of Indian history and discusses the genetic history of India in this Part 1 of a 3-Part talk, delivered in Houston, Texas, on Jan 2nd, 2016.



Raj Vedam of Indian History Awareness & Research (IHAR) highlights the mainstream narrative of Indian history and discusses the history of astronomy India in this Part 2 of a 3-Part talk, delivered in Houston, Texas, on Jan 2nd, 2016.

India is the second most populous country in the world with a population of 1.21 billion [1]. About 4,635 different population groups are spread across the country [2]. Exorbitant as it may sound, existence of at least 50–60 thousand essentially endogamous groups has been reported in the country [3]–[4]. The present day Indian population is divided into tribal and non-tribal groups. Tribal populations constitute 8.2% of the total population [5] and are considered to be the indigenous populations of India [6]–[8]. The tribal groups of India belong to four broad linguistic families: Austro-Asiatic, Dravidian, Indo-European and Tibeto-Burman [9]. The Indo-European and Dravidian speaking populations are considered to be the major contributors to the development of Indian culture and society [10]. Both Austro-Asiatic and Dravidian speaking tribes belong to the primary pre-historic populations of India [7], [11]. Tibeto-Burman speakers also include many tribal populations but their geographical distribution is largely restricted to the North-Eastern region of India. India thus exhibits an enormous genetic, cultural and linguistic diversity which can partly be attributed to its position at the tri-junction: with Africa in the west, Eurasia in the north and the Orient in the east. The country's unique location gives rise to a great variety of environmental conditions and associated biodiversity [12] which in turn has attracted people from all over the globe.



Archaeological and paleontological evidence dating back to the middle and late Pleistocene era points towards early human occupation of the Indian subcontinent [13]–[16]. Similar evidence of antiquity of Indian populations has been established by genetic marker studies. The high levels of gene diversity and coefficients of gene differentiation obtained using autosomal markers for Indian populations are a testimony of both, the antiquity and the complex population structure, of this massive human conglomeration existing in the southern part of Asia [17]–[19]. Recent genetic studies based on mtDNA showing the high frequency of mitochondrial lineages with greater age, high diversity and wide distribution amply demonstrate the prehistoric existence of mankind on the Indian subcontinent [20]–[21]. Similar analyses of Y chromosome variation based on both bi-allelic and microsatellite markers have documented the existence of substantially deep rooted lineages among Indian populations buttressing the claim of early habitation of humans on the Indian subcontinent [22]–[25].

The unique and complex structure of the Indian population is attributed to the multiple waves of migration and the resultant gene-flow which occurred in the past [12], [26]. Some scholars have provided evidence to explain the origin and migration of the major linguistic families extant in India [25], [27]. It is worth mentioning that speakers of Austro-Asiatic language in India are exclusively tribal, which may be indicative of their being one of the oldest inhabitants of India [28], [29]. The arrival of the Indo-European speakers via the Northern corridor of India around 3,500–4,000 years ago is believed to be responsible for one of the major influxes of people in the Indian subcontinent [30], followed later by the infiltration of colonizers from different parts of the world. Thus, several studies have affirmed the influence of Eurasian and Asian populations on the Indian gene pool [23]–[24], [31]–[34].



Within this complex scenario, many interaction models such as gene-language, gene-geography and gene-ethnicity have been contested. Previous studies have shown inverse correlation between genetic affinities and geographical distance [11], [35]. Significant genetic differentiation between caste and tribal populations has been reported [31], [33], [36], as against a model which suggests that there is considerable sharing of Pleistocene heritage among them with a limited gene flow [34]. Similarly, congruence between language and genes has been proposed by various scholars [9], [37]–[38] along with a competing view supporting that genetic affinities may not necessarily be dependent on linguistic similarities [39]–[41]. Although each study has contributed significantly to understanding the role of language, culture and geography in relation to the genetic affiliation and demographic history of Indian populations; a major limitation in them has been the poor representation of Indo-European speaking tribal populations. This is a critically important limitation since the Indo-European speaking tribes provide ample opportunity for examining the influence of linguistic assimilation on the genomic diversity of India.

Keeping the above in view, we present an analysis based on the study of 48 bi-allelic markers in nine Indo-European speaking tribal groups of Southern Gujarat which lies in the western part of India. The main objectives of the study were (a) to study the distribution of Y haplogroups; (b) to study the relative influence of language, geography or ethnicity on the genetic structure of populations using the pattern of Y haplogroup clustering and finally (c) to relate the observed pattern of Y haplogroup clustering with the Y chromosome lineages which arrived in India largely from the Northern corridor at different points of time. To achieve the study objectives the results were first compared with published studies on the Indian populations and then with available data on the Eurasian populations. The Indian populations were selected keeping in view the availability of data, their linguistic and socio-culture status and geographical position. Similarly, the Eurasian populations for which published sources were available were considered for analysis since the historical migrations from these regions are known.


Figure 1. Sampling areas; Map of India highlighting Gujarat (top); Regions of study pointed out in the map of Gujarat (bottom).

The frequency distribution of Y chromosome haplogroups among the study populations along with the phylogenetic relationship between them is presented in Figure 2. The side branches on the tree represent Y SNP for which the ancestral state was observed, while the direct branch represents Y markers for which the mutant allelic state was observed; leading to haplogroup designation in the particular sample. Analysis of 48 bi-allelic markers of the Y chromosome showed 13 paternal lineages that were distributed throughout haplogroups H, R, J, C, F, L, K and Q. Haplogroup H represented the most frequently occurring haplogroup (40.14%) followed by groups R (28.17%), J (10.21%) and C (8.45%) respectively. Sparse distribution was observed for the lineages F*, L1, Q3 and K* across all the populations.