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

BACKGROUND: The "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. RESULTS: The 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. CONCLUSION: Our 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

Allelic variants of DYX1C1 are not associated with dyslexia in India

Dyslexia is a hereditary neurological disorder that manifests as an unexpected difficulty in learning to read despite adequate intelligence, education, and normal senses. The prevalence of dyslexia ranges from 3 to 15% of the school aged children. Many genetic studies indicated that loci on 6p21.3, 15q15-21, and 18p11.2 have been identified as promising candidate gene regions for dyslexia. Recently, it has been suggested that allelic variants of gene, DYX1C1 influence dyslexia. In the present study, exon 2 and 10 of DYX1C1 has been analyzed to verify whether these single nucleotide polymorphisms (SNPs) influence dyslexia, in our population. Our study identified 4 SNPs however, none of these SNPS were found to be significantly associated with dyslexia suggesting DYX1C1 allelic variants are not associated with dyslexia

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

Abstract Background The "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. Results The 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. Conclusion Our 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.</p

The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage-0

Ur additional complete mtDNA sequence of M2 lineage (labeled as R102, T3, T11 and T27) are acquired from published sources [] has been used for tree reconstruction. Suffixes A, C, G, and T indicate transversions, "d" signifies a deletion and a plus sign (+) an insertion; recurrent mutations are underlined. The prefix "@" indicates back mutation. The coalescent estimates were calculated as per [] and [] presented as bold and Italic respectively.<p><b>Copyright information:</b></p><p>Taken from "The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage"</p><p>http://www.biomedcentral.com/1471-2148/8/230</p><p>BMC Evolutionary Biology 2008;8():230-230.</p><p>Published online 11 Aug 2008</p><p>PMCID:PMC2528015.</p><p></p

The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage-2

Ur additional complete mtDNA sequence of M2 lineage (labeled as R102, T3, T11 and T27) are acquired from published sources [] has been used for tree reconstruction. Suffixes A, C, G, and T indicate transversions, "d" signifies a deletion and a plus sign (+) an insertion; recurrent mutations are underlined. The prefix "@" indicates back mutation. The coalescent estimates were calculated as per [] and [] presented as bold and Italic respectively.<p><b>Copyright information:</b></p><p>Taken from "The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage"</p><p>http://www.biomedcentral.com/1471-2148/8/230</p><p>BMC Evolutionary Biology 2008;8():230-230.</p><p>Published online 11 Aug 2008</p><p>PMCID:PMC2528015.</p><p></p

The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage-1

PD) limits. Panel 'A'- The Bayesian skyline plot (= 10) for India total, derived from complete mtDNA sequences (= 76). Panel 'B'- The Bayesian skyline plot (= 10) for India total, derived from coding region (577–16023) mtDNA sequences (= 76). The time estimates (yBP) were calculated as per []. For comparison, the cold and arid period around the Last Glacial Maximum are also indicated on panel A & B. Panel 'C to F' shows Bayesian skyline plots (= 10) derived from complete mtDNA sequences of eastern (n = 11), central (n = 29), southern (n = 14) and western (n = 22) regions of India respectively.<p><b>Copyright information:</b></p><p>Taken from "The earliest settlers' antiquity and evolutionary history of Indian populations: evidence from M2 mtDNA lineage"</p><p>http://www.biomedcentral.com/1471-2148/8/230</p><p>BMC Evolutionary Biology 2008;8():230-230.</p><p>Published online 11 Aug 2008</p><p>PMCID:PMC2528015.</p><p></p