| 其他摘要 | In southern part of eastern Asia, there are a lot of diversified ethnic groups that can be differentiated by their language, culture and physical appearance. From previous reports, the early settlers from Africa migrated along the “southern route” and reached mainland Southeast Asia (MSEA) ~ 60 thousands ago. Later, some of them migrated northward and entered southern part of East Asia ~ 30-40 thousands ago. Also, there was southward migration island Southeast Asia (ISEA), Oceania and Australia. However, despite their critical role in these peopling histories, the populations in MSEA have rarely been studied for genetic diversity, especially the coastline regions in MSEA, such as Cambodia. The genetic origin and migratary histories of Cambodian populations are yet to be revealed. Located on the southern coast of Indochina Peninsula, Cambodia is the “crossing site” of the “northward” and “southward” migration waves. Thus, Cambodians are important in tracing the origin, and prehistoric peopling in southern part of eastern Asia, Oceania and Australia. In this study, we aim to reveal the comprehensive genetic profiles of Cambodian aborigines. Firstly, we investigated the matrilineal gene pool of 1,054 Cambodians from 14 geographic populations, and we identified 8 novel mtDNA haplogroups, which have very old coalescence ages, ranging from ~55,000 to ~68,000 years; this is congruent with our previous view that the first settlers of modern human reached southern parts of eastern Asia some 60,000 years ago. In addition, most of the common Cambodian haplogroups have the highest diversity among the studied populations, indicating they originated locally in Cambodia before expanding to the surrounding areas during prehistory. Moreover, we observed a relatively close relationship between Cambodians and populations from the Indian subcontinent, Andaman Island, Australia and Madagascar. All of these results suggest that Cambodians are very ancient populations in Asia. Secondly, after systematic analysis of the Y-DNA of 365 male samples from Cambodia, we detected that the most dominant Y-lineage in Cambodians is O2a-M95 (~70%), and it has medium level of haplotype diversity in this region and relatively old TMRCA. From our comprehensive analysis and other previous reports, we postulated that the O2a-M95 lineage originated in coastline regions of southern part of eastern Asia during Palaeolithic period, and the Daic speaking populations are likely the ancestral populations in these regions. Thus, different from their matrilineal gene pool, the major patrilineal component of Cambodians were likely from surrounding populations through massive male population migration, admixture and replacement of the local aboriginal males. Additionally, we also detected low frequency lineages, O3-M122 and O1a-M119, which were originally from the southern part of China and ISEA respectively. We also observed rare lineages (R-M207, C-M130, D1a-N1, J2-M172, K*-M9, Q1-P36.2, F*-M89 and N-M231), which are prevalent in India, Europe and East Asia. Thus, Cambodians have undergone massive sex-biased admixture in history, and they maintained the ancient matrilineal gene pool from the earliest ancestors who firstly settled in MSEA. Howerver, their paternal genetic pool were displaced by massive latter migrators who were from southeast coastline regions of East Asia. Finally, we conducted a systematic analysis of the sub-structure, origin and dispersal patterns of lineage O2a-M95. With many Austro-Asiatic population samples from Cambodia, Thailand and Yunnan province of China, we updated the phylogeny of O2a-M95 by defining 5 sub-branches: O2a1*-M95, O2a1a-F789, O2a1b*-F1252, O2a1b1*-M88 and O2a1b1a-F761, in which the O2a1a-F789 is the most dominant (accounting for 85.22%). In addition, we analysed 127 populations from Asia that harbor the O2a-M95 lineage, and proposed that this lineage may originate in southern parts of eastern Asia among the Daic populations aroun |
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