Tibeto-Burmans in Bengal, and Indians in ancient Malaya

Thanks to the Singapore Genome Variation Project, and some data from Lynn Jorde‘s lab, I added some Tibetans and Malays for a pooled data set of East, Southeast, and some South Asians. The marker density was 70,000. I was curious to explore the various contributions of ancestry from eastern Eurasians into northeast South Asia.

The Tibetans, in particular, seem to be a common “source” population in a lot of places. There are fewer than 10 million Tibetan people, proper, today. But the impact of Tibetan or quasi-Tibetan people historically has been much greater than their current numbers might suggest. Additionally, Tibetans occupy a very wide geographical range, far outside of the Tibetan Autonomous Region of modern China. The majorit of ethnic Tibetans live outside of its political boundaries. The terms “Sino-Tibetan” and “Tibeto-Burman” are both ethno-linguistic terms which point to the affinities of Tibetans in a broader East and Inner Asian context. Not only was the Tibetan Empire of the 7th to 9th centuries a major geopolitical power, but the Tangut state which dominated much of modern Gansu for centuries had Tibetan affinities.

Meanwhile, in the northeastern quadrant of South Asia, Indo-Aryan languages are dominant today. But, Tibeto-Burman, Tai, and Austro-Asiatic languages are all important as well (or at least present). As noted in Strange Parallels, the Tai are most recent arrivals in Southeast Asia proper. This is known from history.

For Southeast Asia various archaeological, philological, and now genetic, data suggest that Austro-Asiatic languages arrived with the first farmers, who emigrated from what is today southern China, in the range of 4,000 years ago. The arrival of Tibeto-Burman languages and peoples to Southeast Asia surely precedes that of the Tai, which dates to 1,000 years ago, but likely postdates the arrival of Austro-Asiatic groups.*

The situation in northeastern South Asia is somewhat confused in terms of period of arrival of the various groups. A few years ago a paper on cholera genetics in Bangladesh reported analysis which indicates that the ancestors of eastern Bengalis received an admixture pulse of East Asian ancestry about 1,500 years ago. And, that a pulse model would suffice. An immediate explanation that came to mind is that these Bengalis mixed with Munda people, who have substantial East Asian ancestry, and speak an Austro-Asiatic language.

In The Genomic Formation of South and Central Asia one model for the emergence of Munda people that fits the data is:

1) An admixture of East Asian people (presumably, Austro-Asiatic farmers), with “Ancestral Ancestral South Indians” (AASI). AASI being indigenous South Asians who lack any West Eurasian ancestry.

2) A mix of this component with “Ancestral South Indians” (ASI), with consists of AASI and a minority ancestry of West Eurasian farmer from Iran.

Presumably there other models which fit the data as well, but even with naive admixture analysis it was long evident to anyone who looked at the Munda were atypical. The Turan/East European ancestry that one can find with classical model-based admixture at various levels in various South Asian populations is always absent in the Munda. Not only that, but they had very high fractions of modal South Asian ancestry combined with the East Asian component.

So can the East Asian ancestry in Bengalis be explained by the Munda? I’ve posted on this topic before, and every time I come to the same conclusion, probably not. Now that I have Tibetan and Malay samples to define a northwest-southeast transect I can say that again, more definitively.

At K = 10 in the admixture plot above you notice that the cluster modal in Malays and Cambodians accounts for almost all the East Asian ancestry in the Austro-Asiatic Munda sample. In Bengalis that component is found, but so is the proportion modal in Tibetans, and also in Han Chinese. The same pattern is found in the Burmese, but with much higher fractions. In fact, let’s compare average fractions between Bengalis and Burmese.

Han Tibetan Austro-Asiatic
Bengali 3% 4% 4%
Burmese 16% 34% 28%

The Han-model component is kind of general. We can’t reject the possibility I think from these proportions that the East Asian ancestry in Bengalis is exactly the same as that in Burmese…though based on Y chromosomal data I do think there is some Munda ancestry in Bengalis. Additionally, Munda people are found in some numbers even today in Bengal, into Bangladesh (the Santhals).

Looking at results from a three-population test the Tibetan(like) contribution to Bengalis seems likely:

outgroup pop1 pop2 f3 f3-error z
AustroAsiatic Dai Telegu -0.00187497 0.00012171 -15.4052
AustroAsiatic Telegu Lahu -0.00182418 0.000124765 -14.6209
AustroAsiatic Malay Telegu -0.00135077 0.0001035 -13.0508
AustroAsiatic Han Telegu -0.00138827 0.000112488 -12.3415
AustroAsiatic Telegu Kinh -0.00158805 0.000130918 -12.1301
AustroAsiatic Miaozu Telegu -0.00142974 0.00011907 -12.0076
AustroAsiatic Telegu She -0.0015296 0.000127609 -11.9866
AustroAsiatic Cambodians Telegu -0.00135761 0.000119312 -11.3786
AustroAsiatic Telegu Tujia -0.00137567 0.000125184 -10.9892
AustroAsiatic Telegu Naxi -0.00106498 0.000123643 -8.61336
AustroAsiatic Telegu Japanese -0.000991272 0.000116507 -8.50824
AustroAsiatic Yizu Telegu -0.00111008 0.000133985 -8.28514
AustroAsiatic Telegu Han_N -0.000844919 0.000122055 -6.92243
AustroAsiatic Telegu Tibetan -0.000414633 0.000109922 -3.77207
AustroAsiatic Telegu Hezhen -0.000428829 0.000116739 -3.67339
AustroAsiatic Xibo Telegu -0.000504054 0.000138498 -3.63943
AustroAsiatic Telegu Burmese -0.000335967 0.000108207 -3.10485
Bengali AustroAsiatic Iranian -0.00331738 7.5938E-05 -43.6853
Bengali Miaozu Telegu -0.00250784 6.12097E-05 -40.9712
Bengali Han Telegu -0.00250669 6.11899E-05 -40.9658
Bengali Telegu Tibetan -0.0022997 5.672E-05 -40.5448
Bengali Telegu Japanese -0.00240064 6.02193E-05 -39.865
Bengali Dai Telegu -0.00253233 6.53283E-05 -38.7632
Bengali Malay Telegu -0.00212941 5.51377E-05 -38.6199
Bengali Xibo Telegu -0.0023685 6.24874E-05 -37.9036
Bengali Telegu Han_N -0.00241445 6.40346E-05 -37.7054
Bengali Telegu Burmese -0.00205009 5.43997E-05 -37.6857
Bengali Telegu Naxi -0.00249315 6.66967E-05 -37.3804

OK, so what do we do with this, and how does it make sense? If you read a book like Land of Two Rivers, you won’t have any sense that an admixture between a Tibeto-Burman people, and Indo-Aryan speakers, occurred in eastern South Asia 1,500 years ago. To a great extent this is “prehistoric,” hidden from us, even if by that period mentions of the fringes of modern Bengal exist in Classical Indian sources. It is clear that many of the people who lived in Bengal were not part of Aryan society.  The later Vedic sources assert this explicitly, mentioning non-Aryan tribes beyond the march.

I currently believe that southern and eastern South Asia were touched by the expansion of Indo-Aryan/Dravidian speaking people after 4,000 years ago. This would make sense in light of the Vedic memory. I also suspect that Austro-Asiatic Munda people arrived after 4,000 years ago into a landscape where the population was AASI, without any West Eurasian influence. By 500 BC it seems that Indo-Aryan culture at least arrived on the edge of Bengal. At this date I suspect most of the tribes living in Bengal were probably already Munda. If the argument in The Rise of Islam and the Bengal Frontier is correct that much of eastern Bengal was not intensively cultivated until after 1000 AD. The period between 500 AD and 1000 AD was also the only one in ancient or medieval India where Bengal was home to the paramount hegemonic power in South Asia, a state ruled by the Pala dynasty.

Meanwhile, Tibeto-Burman people seem to have arrived to the east around 200 BC in the Irrawaddy basin. Rice cultivation in this region dates to 1500 BC. This is 500 years after rice cultivation arrived in northern Vietnam. Presumably then around 200 BC and later there was a transition from Austro-Asiatic languages to Tibeto-Burman langauges (the Mon may be intrusive from Thailand). Somehow I suspect that between 0 and 500 AD a group of Tibeto-Burmans moved up to the coast and arrived in eastern Bengal. Mixing with the native Munda they were probably absorbed by the expansion of Indo-Aryans eastward triggered by the political dominance of the Pala dynasty.

But was the gene flow in one direction? This seems unlikely. All the Burmese samples have South Asian admixture. This can be explained by proximity. But there are signatures of this in Cambodia, and the Malay samples I selected were part of a tight cluster. It seems that the Malay samples also have substantial South Asian admixture. The Indian Ocean economy and Diasporas between 0 AD and 1000 AD, after which Muslims and later Europeans became dominant, is a lacunae in our understanding. The presence of Malagasy and clear Austronesian influence in East Africa indicate a east to west migration. But Indian genetic signatures are found through Southeast Asia as well. Some of this can be chalked up to proximity (Burma) and colonial era contact (Malaysia), but Cambodia is too far for either to be plausible. Curiously, this influence is mostly lacking in Vietnam, or the interior of Southeast Asia. This is strongly suggestive of maritime trade contact. The regions where Indic culture were strong are the regions where there is a genetic signature of South Asians.

At this point I think I’ve established enough about South Asia and Bengal to move on from that. In the future I’m more curious about exploring contacts between South Asia and Southeast Asia, and how it left a cultural and biological impact.

* The 4,000 year date I arrival from the genetic sample and culture which emerges in northern Vietnam’s Red River Valley, and marks the transition between hunter-gatherers to agriculture.

11 thoughts on “Tibeto-Burmans in Bengal, and Indians in ancient Malaya

  1. So is the South Asian component in the Burmese which from previous posts seems quite high (approx 25%) from Bengali due to proximity or South Indians due to maritime trade routes? What is the time for this admixture?

    Also, now that you have Sri Lankan genetic data, what is your opinion on the genetic relation between Bengali and Sinhalese?

    Ps Thanks Razib, I’ve been following you for over a year and I owe you for teaching me so much about my ancestry.

  2. @Razib, I’m sorry, it was Singapore not Sri Lankan! Ignore the last comment but please give me your opinion on the first 2. My apologies, and thanks again

  3. We know that the Tibetans invaded Bengal in the 7th century, and it isn’t unlikely that they may have contributed the ancestry seen.

    I don’t think this was the first incursion, and the swift adoption of Buddhism may have emerged from pre existing contacts with Bengal. One cannot help but notice that despite Tibetan buddhism being based on missionaries and schools from what is now Uttar Pradesh and Bihar, the Tibetan script closely follows the forms of Bengali.

  4. Razib: Meanwhile, Tibeto-Burman people seem to have arrived to the east around 200 BC in the Irrawaddy basin. Rice cultivation in this region dates to 1500 BC. This is 500 years after rice cultivation arrived in northern Vietnam. Presumably then around 200 BC and later there was a transition from Austro-Asiatic languages to Tibeto-Burman langauges (the Mon may be intrusive from Thailand).

    Oakaie samples in NW Burma at 1200-700 BCE in Sagaing Region Burma (basically on the Chindwin tributary of Irawaddy) look autosomally Tibeto-Burman, not Austroasiatic.

    https://reich.hms.harvard.edu/sites/reich.hms.harvard.edu/files/inline-files/Online_pub_science.aat3188.full__0.pdf

    “Oakaie projects close to present-day Myanmar and other Sino-Tibetan speakers”

    “Late Neolithic/Bronze Age Myanmar individuals from Oakaie also do not possess an Austroasiatic genetic signature, in their case being closer to populations speaking Sino-Tibetan languages (including present-day Myanmar), pointing to an independent East Asian origin. “

    Samples date to 3200-2700 BP (so median 2950 BP). Sites with shared material culture themselves date between 1500 BCE and 500 BCE, so assuming cultural continuity you’d guess Tibeto-Burman speakers enter northernmost Myanmar about 1500 BCE (contemporaneous with Shang Dynasty in Sinic terms).

    Not sure of the definition of Irawaddy Basin here though, so can’t say if it’s likely / unlikely for Oakaie-like (Tibeto-Burman) people to have already been present there at e.g. 1000 BCE.

  5. But I would expect the maritime influence to be mostly male mediated but there is not that much of it in that region, especially Y-Haplogroup H. This is not a direct refutation but the theory needs to be worked out more.

  6. There is an update to the SGVP, the SG10K https://www.biorxiv.org/content/early/2018/08/11/390070 whole-genome sequencing data of 4,810 Singaporeans from three diverse ethnic groups: 2,780 Chinese, 903 Malays, and 1,127 Indians.

    Interestingly contrary to the SJW insistance of asserting that ‘race’ is a social construct, the SuppInfo actually has the matrix of self-indentified and genetics inferred ethnicities,

    Inferred|SelfChinese|SelfMalay|SelfIndian|SelfOthers|Total
    InferredChinese|2639|46|17|78|2780
    InferredMalay|13|845|33|12|903
    InferredIndian|7|36|979|105|1127
    Total|2659|927|1029|195|4810

  7. I have a few question:
    -AASI component in Bengalis is from Indo Aryan/IVI or Munda or both? Except East Asian and Baltic part Bengalis doesnt look different from Telegus.
    -Are the Telegu samples from Reddy/Naidu castes or there are few Brahmins as well?
    -Are Malagasy people fro Madagascar technically half Indonesian?

    Han Tibetan Austro-Asiatic
    Bengali 3% 4% 4%
    Burmese 16% 34% 28%

    That suggest Bengalis got East Asian from some Burmese groups, Maybe Chakma?

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