South Asia constitutes a large segmented endogamous society that harbors rich genetic diversity within itself and offers to test several population genetic models derived by linguistic, geographical and cultural boundaries that can have a profound effect on human evolution. Strict endogamous populations, flourished independently with varied socio-cultural and linguistic diversities, nurtured by the vast geographical and ecological system, enriched South Asian diversity tremendously. It is of particular interest to study patterns of genetic affinities among endogamous groups inhabiting small geographical regions within the subcontinent because of their diverse origins and interethnic sepa-ration. The strict practice of endogamy across all social ranks resulted in emergence of population-specific diverse social traditions and development of distinct linguistic dialects. These divergent socially structured population groups provide a varied substratum for understanding variation of a genetic trait, spread of a particular disease and their prehistorical settlement in a geo-graphical area. An understanding of evolutionary history of peopling of South Asia has long been a subject of interest for the researchers working in evolutionary and medical genetics.
During the commencement of this work the largely maternal autochthonous genepool of South Asia started gaining support due to higher resolution studies (Metspalu et al., 2004; Palanichamy et al., 2004) although, the skeleton of macrohaplogroup M, which encompasses 60% of Indian maternal genepool was not resolved completely. Besides this, the gene-culture interaction, caste-tribe continuum and localized haplogroup expansion were some of the basic ques-tions. We therefore added high resolution molecular insights into genetic, linguistic and anthropological background and updated the phylogenetic knowledge about peopling of South Asia.
The questions undertaken for the present work are as follows:
MtDNA haplogroup M comprises more than 60% of the matrilineal diversity of populations living in South Asia. Furthermore, a vast majority of them are autochthonous, not found or almost not found elsewhere in Eurasia, Melanesia and Oceania. Because such Indian M lineages differ profoundly from numerous M lineages found elsewhere, they offer unique insight into the matrilineal heritage of the subcontinent. Several previous studies have suggested that Indian mtDNA lineages, particularly those classified under haplogroup M, have evolved locally in India. However, substantial pro-portions of the M lineages in India have been studied so far only at low molecular resolution and involve insufficient sampling. Due to the scarcity of the data, it is not known, whether the so-called M* lineages detected at variable frequencies across India are more closely related to the local M subclades or to those widely spread in East Asia or Oceania. Is it possible to detect at complete mtDNA sequence resolution level elements of nested
phylogenetic structure that would link South and East Asian populations or either of the two more specifically with Papuans and Australians?
Andaman islanders are classically considered as one of the most remote populations in the world of unknown genetic origin. Often called in anthro-pological literature as Negritos for their dark skin colour and curly hair, different hypotheses on their ancestry have been proposed. It was recently shown that two mtDNA haplogroups, M31 and M32, which occur at fre-quency <0.1% in mainland India, characterize almost all mtDNA lineages in Southern Andaman islanders. We further sought to examine whether the fine internal structuring in M31 and M32 haplogroups phylogeny reconcile with cultural and geographical separations of Andaman islanders?
Since the period of classical genetic markers, Indian social stratification has been one of the most complicated issue to address. Many papers have been devoted to demonstrate differences between the castes, but much less attention has been addressed to numerous tribal people still living in India.
And that irrespective of the fact that there have been hypotheses, based largely on indirect evidence, that the tribal people might be “true auto-chthonous populations” inhabiting India, while the speakers of not only Indo-Aryan but also Dravidian languages, are relative newcomers from the Neolithic period that covers only the last period since the subcontinent has been inhabited by modern humans. What is the reason behind the contrasting distribution of the scheduled castes and scheduled tribes in India? Is it due to social mobility governed by the caste-tribe continuum? Furtheremore, several previous non-genetic studies documented language shift as a com-mon phenomenon acom-mong South Asian populations where several popula-tions have very likely changed their mother tongue. However, none of the molecular studies have been so far aimed at testing this assumption. There-fore we have now asked whether the phenomenon of language shift typical for South Asia as such, or is it primarily a signal of a rapid genetic admix-ture?
One particular, but otherwise representative example of ambiguity in the languages versus genes problem has been the origin of the Austroasiatic speaking people in India. Some influential authors still consider them as autochthonous, pre-Aryan and even pre-Dravidian inhabitants of India, others look to them as very recent newcomers from Southeast Asia.
Therefore, it can be considered as a sort of test question for a geneticist – can one now, with all the new powerful tools to investigate phylogeography of mtDNA (and of the Y chromosome), find ways to answer these questions?
Our preliminary analyses of mtDNA haplogroup R7 at low resolution (HVS-I) showed it’s significantly higher frequency in Austroasiatic (Munda) speaking tribal populations than among other language groups of India.
Therefore, a higher molecular resolution study was designed to test if R7 can be considered as an Austroasiatic (Munda) specific haplogroup?
Like elsewhere in a global context, genetic boundaries and differences in general, among populations of South Asia, are likely governed by several
factors, such as geography, language and culture. Because of its geographic span and, in particular, extremely complex social stratification and also the size of population, we found it important to seek an answer (even if only as a preliminary attempt) to the most general question: Is the South Asian genetic landscape primarily molded by interaction of genes and languages or genes and geography?