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Saturday, March 20, 2010

Genetics of the Mlabri, Austroasiatic hunter-gatherers in Thailand


Shuhua Xu et al., Genetic evidence supports linguistic affinity of Mlabri -- a hunter-gatherer group in Thailand. BMC Genetics, 2010. Open access.
Abstract (provisional)

Background

The Mlabri are a group of nomadic hunter-gatherers inhabiting the rural highlands of Thailand. Little is known about the origins of the Mlabri and linguistic evidence suggests that the present-day Mlabri language most likely arose from Tin, a Khmuic language in Austro-Asiatic language family. This study aims to examine whether the genetic affinity of the Mlabri is consistent with this linguistic relationship, and to further explore the origins of this enigmatic population.

Results

We conducted a genome-wide analysis of genetic variation using more than fifty thousand single nucleotide polymorphisms (SNPs) typed in thirteen population samples from Thailand, including the Mlabri, Htin and neighboring populations of the Northern Highlands, speaking Austro-Asiatic, Tai-Kadai and Hmong-Mien languages. The Mlabri population showed higher LD and lower haplotype diversity when compared with its neighboring populations. Both model-free and Bayesian model-based clustering analyses indicated a close genetic relationship between the Mlabri and the Htin, a group speaking a Tin language.

Conclusion

Our results strongly suggested that the Mlabri share more recent common ancestry with the Htin. We thus provided, to our knowledge, the first genetic evidence that supports the linguistic affinity of Mlabri, and this association between linguistic and genetic classifications could reflect the same past population processes.


While finding out about the Mlabri, an ethnicity I had never before heard of, and confirming that hunter-gatherers of Austroasiatic language do not just exist nowadays in Malaysia, is interesting in itself, what most has provoked my attention is the genetic comparison between various South East Asian ethnicities and the HapMap North Chinese and Japanese samples.

It seems that the paper has come right in time to illustrate the ongoing debate elsewhere on this blog, on whether there is any specific marker to Northern Han (or even Han in general) and other major East Asian populations such as Koreans and Japanese.

What I am realizing is that there is nothing really specific and that these northern populations almost invariably cluster with some of their southern neighbors, which are much more diverse. This really surprises me a bit because I would have expected that the Neolithic of the Yellow River, surely at the origin of the Chinese ethnicity (Han, Hui) would have been created by a somewhat distinct group that we should be able to identify by some genetic marker or set of markers, even if they spread southwards as the Chinese empire did.

Not at all. It seems that such specificity is almost invisible and that the Han (as well as genetically similar Korean and Japanese peoples) are very much unspecific in terms of genetic markers that could be easy to spot. They rather seem like melting pots of lineages which are traced to likely origins in the South of East Asia.

And, as I say this study comes very handy to illustrate this pattern within autosomal DNA as well, with Chinese and Japanese clustering with Hmong-Mien specially and then with Tai-Kadai peoples.

The neighbor-joining (NJ) tree:

The Htin and Mlabri are of course Austroasiatic, even if color-coded differently. JPT stands from Japanese from Tokyo and CHB as Chinese from Beijing (they are standard HapMap samples). The Karen are Tibeto-Burman speakers.

The maximum likelihood (ML) tree:

Careful here because the color-coding is not linguistic. As said before the Karen are Tibeto-Burman speakers and not Austroasiatic as would seem from their clustering and red color. CEU are Caucasoids of European ancestry from Utah and YRI are Yoruba from Nigeria (again standard HapMap samples for comparison). Cursive text is mine.

In this ML tree is maybe where the clustering is more apparent: the whole East Asia is first divided between the Mon and all the rest. They are neighbors of the Karen and linguistically most related to other Austroasiatics but they clearly cluster apart from all.

Then they branch into other Austroasiatics plus Karen (TB) and Tai-Kadai, Hmong-Mien and northern ethnicities. And this last group branches out into Tai (a branch of Tai-Kadai) and an amalgam of other Tai-Kadai (Yao), Hmong-Mien (Hmong) and the northern ethnicities. And only at this stage a North-South divide becomes apparent.

13 comments:

Natsuya said...

Another great East/Southeast Asian autosomal DNA study published last year:

Mapping Human Genetic Diversity in Asia

http://209.85.48.16/4802/123/0/p1004887/Mapping_Human_Genetic_Diversity_in_Asia.pdf

Natsuya said...

According to the paper I posted above, in the NJ tree chart, western Indonesians have notable "red" component which is related to Austro-Asiatic populations.

It reminds me of the status of Austro-Asiatic-related O2a-M95 among western Indonesians in Karafet's study.

Maju said...

Thanks a lot for posting that because, while I had commented before on the HUGO paper, I could only access the supplementary material.

The ML tree alone is very meaningful: first of all it shows East Eurasians (incl. Negritos) as a distinct branch within Eurasia (though the Mon branch out before that); then this Eastern branch splits into a Malay Archipelago branch and a Mainland one. Then the mainland one splits between Austroasiatics (and Karen/Jinuo) and the rest; then the various Tai-Kadai branch out and then the Hmong-Mien and Sino-Japanese.

The Mon early divergence may be because they have Indian blood (not apparent in phenotype but it is in the K-means graph).

It's a complex and interesting structure. And the HUGO ML tree adds understanding of this one, by including ISEA peoples, as well as other Eurasians.

"According to the paper I posted above, in the NJ tree chart, western Indonesians have notable "red" component which is related to Austro-Asiatic populations".

Makes sense, specially if they got some notable blood input from mainland East Asia, as Karafet suggests in the Mid-Late Upper Paleolithic. However their main component is the same as Taiwan Aborigines/Filipinos, also found in South China at lower levels.

On the other hand, Orang Asli show up as a distinct group, even if they speak Austroasiatic. The Mlabri do too, though they don't in the ML tree.

Maju said...

Anyhow, the East Asian components at K=14 can be described as:


Major components:
- Ryukyuan (yellow)
- Diffuse Main East Asian (dark blue), also found in Indian Hymalaya area and Mon
- Austronesian (bright green), also found among Han and Tai-Kadai
- Austroasiatic (red), also in West Indonesia

Minor components:
- Hmong-specific (light blue)
- Melanesian (dark green), also dominant in East Indonesia
- Filipino Negrito (dark purple)
- Malaysia Negrito (dark red)
- Bidayuh (Land Dayaks) (white)
- Mlabri (light purple)

I guess that if they sampled further north, they could find two or three more components (one Ainu, I guess) but that sums it up pretty well anyhow.

Maju said...

I forgot another minor one: Proto-Malay (middle purple)

Maju said...

I'm noticing that the "pure Austronesians" are the Taiwan Aboriginals, the non-Negrito Filipinos and the Mentawai of an archipelago of West Sumatra. This last reminds me of the case of Nias, further North but also having a "pure" Taiwan-Aborigin-like Y-DNA pool.

However the Mentawai are essentially hunter-gatherers (regressed?), keeping pigs and dogs "as pets" but not growing anything. This is pretty strange because, would it be a founder effect from the Austronesian expansion, we should expect farmers. However there's at least another Austronesian hunter-gatherer group in southern Madagascar: the Mikea, which may also have regressed to forager lifestyle.

Natsuya said...
This comment has been removed by the author.
Natsuya said...

I suppose that bright green would support the "Austro-Tai" macro-family theory connecting Daic and Austronesian language families.

And it also reminds me of O1a-M119 found in both of the populations.

Natsuya said...

Mlabri people are 100% O2a-M95 on Y-DNA, and 100% B5a on mtDNA.

Ebizur said...

Maju said,

"Similarly the Yao are Tai-Kadai (Kradai) and not Hmong-Mien as maybe some could interpret from the light blue color."

Most people who have been categorized as "Yao" by the Chinese do speak a Hmong-Mien (aka Miao-Yao) language; the "Mien" part of "Hmong-Mien" is actually the endonym of the Hmong-Mien-speaking majority of the Yao people.

Natsuya said,

"Mlabri people are 100% O2a-M95 on Y-DNA, and 100% B5a on mtDNA."

May I ask where you have found these data on the haploid gene pools of the Mlabri people?

Maju said...

Austro-Tai? Maybe. It does anyhow permeate the (southern?) Han. It also seems too dominant in West Indonesia to be specifically Austroasiatic, as in having expanded "recently" - but who knows?

In Europe at least similar autosomal clusters would seem to correlate best with Late Paleolithic/Epipaleolithic distribution. Neolithic flows do appear clear as belonging to some other cluster - and they are nowhere as massive.

"Mlabri people are 100% O2a-M95 on Y-DNA, and 100% B5a on mtDNA".

Makes sense because they have extremely low diversity (and they are like 300 people). O2a seems to be consistently associated with Austroasiatics, including the Munda, even if it's also common among their Thai and Austronesian neighbors.

"Most people who have been categorized as "Yao" by the Chinese do speak a Hmong-Mien (aka Miao-Yao) language; the "Mien" part of "Hmong-Mien" is actually the endonym of the Hmong-Mien-speaking majority of the Yao people".

You're right. My bad. I'll correct that in the main post. Thanks.

Natsuya said...
This comment has been removed by the author.
Natsuya said...

to Ebizur:

Here are the papers:

Recent Origin and Cultural Reversion of a Hunter–Gatherer Group

http://www.plosbiology.org/article/info:doi%2F10.1371%2Fjournal.pbio.0030071

Comment on “Recent Origin and Cultural Reversion of a Hunter–Gatherer Group”

http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0030269