张亚平院士PNAS藏族人起源研究取得突破

　　

生物通报道，中国科学院昆明动物研究所分子进化与基因组多样性实验室的科学家在藏族人群起源研究方面取得重要突破，相关成果文章Mitochondrial genome evidence reveals successful Late Paleolithic settlement on the Tibetan Plateau发布在最近的PNAS上。

 

该文通讯作者是张亚平院士，博士生赵勉和孔庆鹏研究员等人参与了研究工作。

 

被誉为“世界屋脊”的青藏高原环境恶劣，是人类比较难以生存适应的地区。但是考古学家们已经从青藏高原上发掘出了旧石器，表明三万年前青藏高原上就可能已经有人类居住。只是，这些人有没有克服末次冰盛期的恶劣条件存活下来呢？从考古资料来看，青藏高原上最主要的石器——细石器，既有华北细石器的特点，也承袭了一些当地旧石器的特色，这表明新石器时期的青藏高原人类很可能接受了当地旧石器人类的文化影响甚至是他们的遗传组份。

 

目前，对现代藏族人的传统遗传研究以及以线粒体DNA和Y染色体为遗传标记的研究基本都认为藏族的祖先是新石器时代从中国北方西迁的移民，这同历史记载是相符的。但现在的藏族人中是否存在旧石器晚期进入青藏高原的现代人祖先的遗传组份呢？

 

由于以前有关藏族的遗传研究分辨率不足、样本量偏小、采样自藏族最主要聚居地——西藏的样本更少，这些都使得以前的研究难以判断藏族群体中是否存在的古老的遗传组份。

 

张亚平院士考虑到现在各地区尤其是东亚的线粒体DNA系统发育背景已经比较清晰，带领博士生赵勉和孔庆鹏研究员等采集了覆盖藏族在中国所有主要聚居地（西藏、青海、甘肃、四川及云南）的680份藏族人群样本（包括西藏地区样本388份），较全面而系统地进行了现代藏族人母系遗传结构的研究。

 

其结果表明，现代藏族人98％左右的母系遗传组份可以追溯至新石器时期以来迁入青藏高原的中国北方人群，这与之前的历史记载以及遗传研究结果是一致的。

 

但值得注意的是，其研究也发现了一个特殊的新基部组份——单倍型类群M16。与源自中国北方人群的母系遗传组份不同的是，类群M16直接从欧亚大陆建群类群M分化而来，且基本只能在藏族群体中观测得到。而基于多种时间估算方法均提示该类群的分化年龄较古老(>2.1万年)，甚至可以追溯到末次冰盛期之前。

 

对该结果最合理的解释是，M16类群很可能代表了旧石器晚期即已定居青藏高原的现代人类祖先延续至今的母系遗传组份。与此同时，在青藏高原腹心地带拉萨附近有一个人类手印脚印的旧石器遗址，该遗迹的估算时间（2.06-2.17万年）和M16类群的年龄很接近，这也在一定程度上支持了上述观点。

 

该项研究工作提示，现代人类祖先在旧石器晚期即已克服恶劣的气候及地理条件，成功定居于“世界屋脊”——青藏高原，因而很好地解决了长期以来考古学、历史学及遗传学领域关于“人类最早何时成功定居于青藏高原”的争论。同时也从遗传上进一步证实，现今绝大多数藏族事实上源自新石器时期以来迁入青藏地区的中国北方人群。

（生物通 小茜）

生物通推荐原文检索

Mitochondrial genome evidence reveals successful Late Paleolithic settlement on the Tibetan Plateau

Mian Zhaoa,b,1, Qing-Peng Konga,c,1,2, Hua-Wei Wangd, Min-Sheng Penga,b, Xiao-Dong Xiee, Wen-Zhi Wanga,b, Jiayangf, Jian-Guo Duang, Ming-Cui Caih, Shi-Neng Zhaoh, Cidanpingcuoi, Yuan-Quan Tuj, Shi-Fang Wua, Yong-Gang Yaok, Hans-Jürgen Bandeltl and Ya-Ping Zhanga,c,d,2

+ Author Affiliations

 

aState Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan Province, China;

bGraduate School of the Chinese Academy of Sciences, Beijing 100049, China;

cKIZ/CUHK, Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming 650223, China;

dLaboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming 650091, Yunnan Province, China;

eKey Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, Gansu Province, China;

fClinical Laboratory, People's Hospital of Shigatse Prefecture, Shigatse 857000, Tibet Autonomous Region, China;

gClinical Laboratory, People's Hospital of Nakchu Prefecture, Nakchu 852000, Tibet Autonomous Region, China;

hBlood Center of Liangshan Yi Autonomous Prefecture, Xichang 615000, Sichuan Province, China;

iBlood Center of Tibet, Lhasa 850000, Tibet Autonomous Region, China;

jYunnan Kunming Blood Center, Kunming 650106, Yunnan Province, China;

kKey Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China; and

lDepartment of Mathematics, University of Hamburg, 20146 Hamburg, Germany

↵1M.Z. and Q.-P.K. contributed equally to this work.

 

Edited by Richard G. Klein, Stanford University, Stanford, CA, and approved October 21, 2009 (received for review July 14, 2009)

 

【Abstract】

Due to its numerous environmental extremes, the Tibetan Plateau—the world's highest plateau—is one of the most challenging areas of modern human settlement. Archaeological evidence dates the earliest settlement on the plateau to the Late Paleolithic, while previous genetic studies have traced the colonization event(s) to no earlier than the Neolithic. To explore whether the genetic continuity on the plateau has an exclusively Neolithic time depth, we studied mitochondrial DNA (mtDNA) genome variation within 6 regional Tibetan populations sampled from Tibet and neighboring areas. Our results confirm that the vast majority of Tibetan matrilineal components can trace their ancestry to Epipaleolithic and Neolithic immigrants from northern China during the mid-Holocene. Significantly, we also identified an infrequent novel haplogroup, M16, that branched off directly from the Eurasian M founder type. Its nearly exclusive distribution in Tibetan populations and ancient age (>21 kya) suggest that M16 may represent the genetic relics of the Late Paleolithic inhabitants on the plateau. This partial genetic continuity between the Paleolithic inhabitants and the contemporary Tibetan populations bridges the results and inferences from archaeology, history, and genetics.