XM. Zhang, et al., "Y-chromosome diversity suggests southern origin and Paleolithic backwave migration of Austro-Asiatic speakers from eastern Asia to the Indian subcontinent."
Analyses of an Asian-specific Y-chromosome lineage (O2a-M95)—the dominant paternal lineage (60.65% on average) in Austro-Asiatic (AA) speaking populations, who are found on both sides of the Bay of Bengal—led to two competing hypothesis of this group’s geographic origin and migratory routes. One hypothesis posits the origin of the AA speakers in India and an eastward dispersal to Southeast Asia, while the other places an origin in Southeast Asia with westward dispersal to India.
Here, we collected samples of AA-speaking populations from mainland Southeast Asia and southern China and then analyzed both the Y-chromosome and mtDNA diversities. Combining our samples with previous data, we generated a comprehensive picture of the O2a-M95 lineage in Asia, including both AA and Daic speaking populations.
We demonstrated that the O2a-M95 lineage originated in the southern East Asia among the Daic-speaking populations ~20-40 thousand years ago and then dispersed southward to Southeast Asia after the Last Glacial Maximum before moving westward to the Indian subcontinent. This migration resulted in the current distribution of this Y-chromosome lineage in the AA-speaking populations. Further analysis of mtDNA diversity showed a different pattern, supporting a previously proposed sex-biased admixture of the AA-speaking populations in India.
2 comments:
Excellent, I am looking forward to this one. Zhang et al already sampled Austro-Asiatic speakers from Cambodia, Thailand, and Yunnan, however. I hope they will do a thorough job of China proper, though, because that may be where most of the basal diversity is. I also hope they actually sampled India.
The dates are far older than any present estimates, which is strange. Y-Full, Karmin et al, and Hallast et al (corrected for mutation rate) all put the TMRCA of O2a1-M95 at about 11 thousand years ago, give or take a few millennia.
The next few nodes down to O2a1a1b-F1252 all follow rapidly, indicating an expansion around this time (my guess would be among sedentary foragers in the Yangtze region, maybe very early Neolithic). These early branches are quite rare in Southeast Asia, making up only 3% of O2a1 (11/343) observed in Zhang's earlier study. It doesn't seem to be common in the Vietnamese either, at 0/15 KHV carrying O2a1. Among the Yunnan Dai (CDX) 8/22 O2a1 men are O2a1a1b. The only JPT (Japanese), CHN (Fujian), and CHB (Beijing) O2a1 samples are all O2a1a1b, while 2/4 CHS (southern Han) O2a1 samples are O2a1b-CTS10007. This is very inadequate data but does suggest the older branches may be proportionally more common in East than in Southeast Asia.
The large majority of O2a1, at least in Southeast Asia, belongs to two younger clades, O2a1a1a-M88 and O2a1a2-F789, both about 5000 years old (give or take a couple thousand years). Both are also present among Han Chinese and Dai. O2a1a1a-M88, though better known, is actually much less common in most populations, representing only 11% of the O2a1 in Zhang's 2014 Austro-Asiatic sample. It is virtually non-existent in India (not one of Kumar's 433 Munda O2a1 samples had M88) and very scarce in ISEA as well. It is, however, predominant among the Vietnamese (26/34 O2a1) and the CDX Dai (12/22 O2a1). It also shows up in some strange places, like Samoa.
O2a1a2-F789 forms 86% of the O2a1 in Zhang's 2014 survey. I am only aware of 5 fully sequenced Indian O2a1 samples, but all of them are F789, as are the 3 samples from Borneo in Karmin et al (the latter also tentatively places 13 Malays in the same clade). This suggests that F789 is also the majority in South Asia and ISEA.
The most plausible scenario to me would be that M88 and F789 mark the most successful clans of Neolithic pioneers - dryland rice farmers, together with the usual hunters, traders, and bandits - who spread from Southern China into Mainland Southeast Asia (and on into India and perhaps ISEA) during the 3rd millennium BC or thereabouts. Presumably at least some spoke early Austro-Asiatic languages.
"The most plausible scenario to me would be that M88 and F789 mark the most successful clans of Neolithic pioneers - dryland rice farmers, together with the usual hunters, traders, and bandits - who spread from Southern China into Mainland Southeast Asia (and on into India and perhaps ISEA) during the 3rd millennium BC or thereabouts".
An idea I have long accepted. So much so that Maju banned me from commenting on his blog because of my insistence on the matter. Five thousand years is close to when it appears that the earlier 'Papuan' type in SE Asia was replaced by a 'Mongoloid' type.
"Presumably at least some spoke early Austro-Asiatic languages".
Extremely likely to be so.
"The next few nodes down to O2a1a1b-F1252 all follow rapidly, indicating an expansion around this time (my guess would be among sedentary foragers in the Yangtze region, maybe very early Neolithic)".
Possibly originating even further north, especially considering that O2b is spread north of China. The Chinese Neolithic looks to have originated between the middle reaches of the Yangtze and Yellow Rivers.
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