The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage

Abstract

BackgroundThe "out of Africa" model postulating single "southern route" dispersal posits arrival of "Anatomically Modern Human" to Indian subcontinent around 66–70 thousand years before present (kyBP). However the contributions and legacy of these earliest settlers in contemporary Indian populations, owing to the complex past population dynamics and later migrations has been an issue of controversy. The high frequency of mitochondrial lineage "M2" consistent with its greater age and distribution suggests that it may represent the phylogenetic signature of earliest settlers. Accordingly, we attempted to re-evaluate the impact and contribution of earliest settlers in shaping the genetic diversity and structure of contemporary Indian populations; using our newly sequenced 72 and 4 published complete mitochondrial genomes of this lineage.ResultsThe M2 lineage, harbouring two deep rooting subclades M2a and M2b encompasses approximately one tenth of the mtDNA pool of studied tribes. The phylogeographic spread and diversity indices of M2 and its subclades among the tribes of different geographic regions and linguistic phyla were investigated in detail. Further the reconstructed demographic history of M2 lineage as a surrogate of earliest settlers' component revealed that the demographic events with pronounced regional variations had played pivotal role in shaping the complex net of populations phylogenetic relationship in Indian subcontinent.ConclusionOur results suggest that tribes of southern and eastern region along with Dravidian and Austro-Asiatic speakers of central India are the modern representatives of earliest settlers of subcontinent. The Last Glacial Maximum aridity and post LGM population growth mechanised some sort of homogeneity and redistribution of earliest settlers' component in India. The demic diffusion of agriculture and associated technologies around 3 kyBP, which might have marginalized hunter-gatherer, is coincidental with the decline of earliest settlers' population during this period.

Dopaminergic D4 receptor polymorphism among 24 populations of India: an anthropological insight

“…The presence of the human ancestral 4R allele at significant frequencies in all Indian populations, irrespective of their tribe and caste status, supports the common genetic substratum of the Indian population proposed previously (Saraswathy et al, 2010). Moreover, the high frequency of progenitor 4R allele among the south Indian and east Indian populations belonging to Proto-Australoid ethnic elements and Dravidian and Austro-Asiatic speakers, respectively, is strongly supportive of the view that Proto-Austaloid groups were the earliest settlers in India and might have diversified into two groups in the course of human evolution in the region (Kumar et al, 2008). Furthermore, studies conducted on different population groups of eastern India (Bhaduri et al, 2007), and southern India (Ghosh and Seshadri, 2005) also found the 4R allele to be the most prevalent.…”

“…Almost all the tribes, except for those of the north-eastern region, are found to have Proto-Australoid ethnic elements, though in varying degrees. Specifically, Austro-Asiatic and Dravidianspeaking tribal groups of India are reported to be modern representatives of the earliest settlers of the subcontinent (Kumar et al, 2008), who would possibly have had the socalled Proto-Australoid ethnic elements. The evolution of the DRD4 48-bp repeat polymorphism among the human lineage is not very clear.…”

The Dazzling Diversity and the Fundamental Unity: Peopling and the Genomic Structure of Ethnic India

“…Based on these patterns, it has been suggested that the Austro-Asiatic speakers are autochthones and possibly the earliest settlers of India (Basu, Mukherjee et al, 2003;Kumar, Padmanabham et al, 2008). Recent results on Y-chromosomal markers provide further support for this inference.…”

“…They also show the highest frequency (about 20%) of sub-lineage M2, which has the highest nucleotide diversity within a fast evolving segment (HVS1) of the mtDNA compared to other sublineages (Kumar, Padmanabham et al, 2008). Based on these patterns, it has been suggested that the Austro-Asiatic speakers are autochthones and possibly the earliest settlers of India (Basu, Mukherjee et al, 2003;Kumar, Padmanabham et al, 2008).…”

“…Molecular genetic diversity studies on Indian ethnic populations have primarily used mtDNA and NRY markers (Basu, Mukherjee et al, 2003) (Sengupta, Zhivotovsky et al, 2006;Bamshad, Kivisild et al, 2001;Kivisild, Bamshad et al, 1999;Kumar, Padmanabham et al, 2008;Underhill, Myres et al, 2010); the number of studies that have used autosomal markers have been comparatively fewer. Most past studies that have used autosomal markers, have either been based on a restricted set of loci (Consortium 2008;Rosenberg, Mahajan et al, 2006), or have been based on a large set of markers but on a small number of individuals or populations, although there are some exceptions (Abdulla, Ahmed et al, 2009;Reich, Thangaraj et al, 2009;Basu, SarkarRoy et al, 2016).…”