Kumar Satish, Padmanabham P B S V, Ravuri Rajasekhara R, Uttaravalli Kiran, Koneru Padmaja, Mukherjee P Aditi, Das B, Kotal M, Xaviour D, Saheb S Y, Rao V R
Anthropological Survey of India, 27 Jawaharlal Nehru Road, Kolkata 700 016, India.
BMC Evol Biol. 2008 Aug 11;8:230. doi: 10.1186/1471-2148-8-230.
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.
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.
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.
“走出非洲”模型假设单一的“南部路线”扩散，认为“解剖学上的现代人”在距今约6.6 - 7万年前抵达印度次大陆。然而，由于过去复杂的人口动态和后来的迁移，这些最早定居者对当代印度人群的贡献和遗传遗产一直存在争议。线粒体谱系“M2”的高频率，与其更长的年代和分布情况相符，表明它可能代表了最早定居者的系统发育特征。因此，我们试图重新评估最早定居者在塑造当代印度人群遗传多样性和结构方面的影响和贡献；使用我们新测序的该谱系的72个以及已发表的4个完整线粒体基因组。
M2谱系包含两个深度分化的子分支M2a和M2b，约占所研究部落线粒体DNA库的十分之一。详细研究了M2及其子分支在不同地理区域和语言语系部落中的系统地理分布和多样性指数。此外，将M2谱系的人口历史重建作为最早定居者成分的替代指标，结果显示具有明显区域差异的人口事件在塑造印度次大陆复杂的种群系统发育关系网络中起了关键作用。
我们的结果表明，印度南部和东部地区的部落以及印度中部讲达罗毗荼语和南亚语系的人群是次大陆最早定居者的现代代表。末次盛冰期的干旱以及末次盛冰期后的人口增长使印度最早定居者成分出现了某种程度的同质化和重新分布。大约在距今3000年前农业及相关技术的人口扩散可能使狩猎采集者边缘化，这与这一时期最早定居者人口的减少相吻合。
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