基因研究证实印度人源于南北两个祖先群体

2009-09-25 admin 新华网
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英国《自然》杂志24日刊登文章说,迄今规模最大的关于印度人的基因测序证实,今天的印度人起源于一南一北两个不同的祖先群体。这项基因研究还证实,印度的种姓制度已有几千年历史。

印度拥有全球约六分之一的人口,但对其基因特征的研究却一直较少。美国和印度研究人员在这次基因研究中,分析了来自不同地点、不同种姓、不同部族的25个人口群落,涵盖了全印度的人口基因特征。

结果显示,印度人起源于一南一北两个不同的祖先群体,其中北方祖先群体的基因与今天中东、中亚和欧洲人的基因相近,而南方祖先群体的基因比较独特,与南亚大陆以外其他任何人群的基因都不相近。今天大部分印度人都含有来自这两个祖先群体的基因。

研究人员说,基因分析还显示印度有一些不同人群在同一个村庄里生活了几千年,却从来没有交换过基因,这证实只允许内部通婚的印度种姓制度已有几千年的历史。研究人员提醒说,需要注意这种由于严格的内部通婚而引起的遗传疾病风险。

此前,历史学家和考古学家已对印度人的起源得出过类似的基本结论,但《自然》为这篇封面文章配发的评论说,这一研究对印度人祖先基因图谱的精确分析、对其祖先基因的混杂和变化趋势等结论都是全新的重要进展,对印度的人类学、医学甚至社会学等研究都有深远意义。

原始出处:

Nature 461, 489-494 (24 September 2009) | doi:10.1038/nature08365

Reconstructing Indian population history

David Reich1,2,5, Kumarasamy Thangaraj3,5, Nick Patterson2,5, Alkes L. Price2,4,5 & Lalji Singh3

1 Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
2 Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, USA
3 Centre for Cellular and Molecular Biology, Hyderabad 500 007, India
4 Departments of Epidemiology and Biostatistics, Harvard School of Public Health, Boston, Massachusetts 02115, USA
5 These authors contributed equally to this work.
6 Correspondence to: David Reich1,2,5Lalji Singh3 Correspondence and requests for materials should be addressed to D.R. or L.S.

India has been underrepresented in genome-wide surveys of human variation. We analyse 25 diverse groups in India to provide strong evidence for two ancient populations, genetically divergent, that are ancestral to most Indians today. One, the 'Ancestral North Indians' (ANI), is genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the 'Ancestral South Indians' (ASI), is as distinct from ANI and East Asians as they are from each other. By introducing methods that can estimate ancestry without accurate ancestral populations, we show that ANI ancestry ranges from 39–71% in most Indian groups, and is higher in traditionally upper caste and Indo-European speakers. Groups with only ASI ancestry may no longer exist in mainland India. However, the indigenous Andaman Islanders are unique in being ASI-related groups without ANI ancestry. Allele frequency differences between groups in India are larger than in Europe, reflecting strong founder effects whose signatures have been maintained for thousands of years owing to endogamy. We therefore predict that there will be an excess of recessive diseases in India, which should be possible to screen and map genetically.