February 7, 2014

Mitochondrial lineages from Myanmar

Myanmar, also known as Burma, has been one of those blind spots in the mapping of human genetics. Finally now we get to know something about the peoples of this SE Asian multiethnic state, although there are limitations because the sampling was performed among refugees in Thailand.

Monica Summerer et al., Large-scale mitochondrial DNA analysis in Southeast Asia reveals evolutionary effects of cultural isolation in the multi-ethnic population of Myanmar. BMC Evolutionary Biology 2014. Open accessLINK [doi:10.1186/1471-2148-14-17]

Abstract

Background

Myanmar is the largest country in mainland Southeast Asia with a population of 55 million people subdivided into more than 100 ethnic groups. Ruled by changing kingdoms and dynasties and lying on the trade route between India and China, Myanmar was influenced by numerous cultures. Since its independence from British occupation, tensions between the ruling Bamar and ethnic minorities increased.

Results

Our aim was to search for genetic footprints of Myanmar’s geographic, historic and sociocultural characteristics and to contribute to the picture of human colonization by describing and dating of new mitochondrial DNA (mtDNA) haplogroups. Therefore, we sequenced the mtDNA control region of 327 unrelated donors and the complete mitochondrial genome of 44 selected individuals according to highest quality standards.

Conclusion

Phylogenetic analyses of the entire mtDNA genomes uncovered eight new haplogroups and three unclassified basal M-lineages. The multi-ethnic population and the complex history of Myanmar were reflected in its mtDNA heterogeneity. Population genetic analyses of Burmese control region sequences combined with population data from neighboring countries revealed that the Myanmar haplogroup distribution showed a typical Southeast Asian pattern, but also Northeast Asian and Indian influences. The population structure of the extraordinarily diverse Bamar differed from that of the Karen people who displayed signs of genetic isolation. Migration analyses indicated a considerable genetic exchange with an overall positive migration balance from Myanmar to neighboring countries. Age estimates of the newly described haplogroups point to the existence of evolutionary windows where climatic and cultural changes gave rise to mitochondrial haplogroup diversification in Asia.

The main sampled ethnic group are the Karen, who live at the border with Thailand, but the Bamar or Burmans, the largest ethnic group, were also sampled in big numbers. 

Fig. 2.- Origin of samples and mitochondrial haplogroup distribution of Southeast Asian populations. Although most of the study participants originated from Karen State (red), a broad sample spectrum from nearly all divisions and states of Myanmar (a) was included in this study. b shows the haplogroup distributions of populations from Myanmar and four other Southeast Asian regions. In the white insert box the haplogroup heterogeneity of two ethnic groups of Myanmar is illustrated. The hatched area in the map surrounding the border between Myanmar and Thailand shows the main population area of the Karen people. The Bamar represent the largest ethnic group (68%) in Myanmar. The size of the pie diagrams corresponds to sample size.

The smaller samples are only detailed in the supplementary data for what I have seen, so I will not discuss them right now (maybe in an update?). 

Overall all SE Asians including the Southern Han from Hong-Kong appear similar in broad terms. Excepted Laos, this relative similitude is quite apparent in figure 3:

Fig. 3.- Multi-dimensional scaling plot of pairwise Fst-values and haplogroup distribution of populations from Myanmar and 12 other Asian regions. A distinct geographic pattern appeared in the multi-dimensional scaling plot (Stress = 0.086; R2 = 0.970) of pairwise Fst-values: The Myanmar sample fitted very well within the Southeast Asian cluster, the Central Asian populations formed a second cluster, the Korean sample represented East Asia, the Afghanistan population was representative for South Asia and Russia symbolized Western Eurasia. The main haplogroup distributions are displayed as pie charts. The size of the pie diagrams corresponds to sample size. The proportion of N-lineages (without A,B and R9’F) increases from very low percentages in Southeast and East Asia over 50% in Central Asia to more than 75% in Afghanistan and 100% in the sample of Russian origin. The proportion of the American founding haplogroups A,B,C and D displayed an interesting pattern: from inexistent in Russians it increased to more than 50% in East Asian Korea.

Looking at the particular differences in haplogroup frequencies, I'd say that the Thai are quite unremarkable, while the other populations show some peculiarities:
  • Karen: higher frequencies of R9/F, A, C and G
  • Bamar: much higher M* (and extremely diverse)
  • Laotian: higher frequencies of B and M7
  • Vietnamese: more B and N*
  • South Han (Hong-Kong): more D

It is very notable the high diversity of paragroup M* among the Bamar. The authors notice that not more than three individuals shared each different subhaplogroup, what points to a very high diversity within haplogroup M. I don't have time right now to ponder the various lineages, some of which are newly described, but I probably will in the future, because, together with the high diversity in NE India, they have the potential of shifting the paradigm of Asian colonization by H. sapiens a bit towards the East.

The various M* and other novel haplogroups described in Myanmar is shown in fig. 4. Haplogroups M90 and M91 are new basal M sublineages, along with three other unnamed private lineages, which also appear as basal. Also M20a, M49a and G2b1a are new sublineages further downstream. Within N/R, another newly described lineage is B6a1.

The Bamar are extremely diverse not just within M*:
... the haplogroup composition of Bamar was exceptionally diverse with 80 different haplogroups and a maximum of 6 samples in the same haplogroup (Figure 4).

On the other hand, the Karen show the signs of genetic isolation instead, with large concentrations in the same haplogroups.

Interestingly, the authors think that rather than being a receiver, Myanmar was a major source of population to its neighbors:
Migration analyses of Myanmar and four Southeast Asian regions displayed a vivid exchange of genetic material between the countries and demonstrated a strong outwards migration of Myanmar to all analyzed neighboring regions (for details see Additional file 4: Table S4).

This influence is most intense to Laos, Thailand and South China, while things are more balanced regarding Vietnam instead.

4 comments:

  1. I an trying to understand this line "Migration analyses of Myanmar and four Southeast Asian regions displayed a vivid exchange of genetic material between the countries and demonstrated a strong outwards migration of Myanmar to all analyzed neighboring regions (for details see Additional file 4: Table S4)."

    The Bamar relocated to Central Burma in the 7-8th century from Yunnan province. However, Laos, Thailand and Vietnam have been popiulated even before 1st century BC. Is it possible Supplemental Table S4 talks about ancient Yunnanite population relocating to Laos, Vietnam and Central Burma at various times?

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    1. I understand that they mean in a much broader period of time, including much of the Prehistory, since long before modern ethnicities existed as we know them.

      My interpretation is rather that (roughly) Vietnam and Myanmar were very possibly the two more important areas in the initial (and maybe also later) population of SE Asia by Homo sapiens and by extension of all East Asia and Australasia. If you try to understand modern populations and their inferred history from a merely historical approach, you will unavoidably miss a lot. Written history is just 2-4 thousand years old, the actual (pre-)history of Homo sapiens in Asia is 100,000 years old. So if it was a Kinder egg, you'd be discussing the thin foil package while they'd be actually talking of the toy and the chocolate egg.

      Notice also that they are talking of Myanmar and not Yunnan. While the two countries have obvious relations since "always", Yunnan is much better surveyed and known and still Myanmar has shown to have even more and distinctive basal diversity in a single exiles' survey. We are not talking of Tibeto-Burman "migrations" (conquests) but about the populations who have been living in the area long long before even Tibeto-Burman existed as such (who now in most cases speak Tibeto-Burman and identify themselves as such but once their ancestors were something else, possibly Austroasiatic in the Neolithic and who knows before that).

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    2. If you want to expand your mind towards a deeper understanding of the population of Asia (and by extension all Earth except Africa) by our species, I would suggest the following introductory entries (from this blog and hence always my opinion, of course):

      → http://forwhattheywereweare.blogspot.com/2013/06/synthesis-of-early-colonization-of-asia.html (basic scheme of how things went some 100-50,000 years ago after leaving Africa and Arabia)

      → http://forwhattheywereweare.blogspot.com/2011/01/zomia-and-rivers-of-se-asia.html (discussing the geography of SE Asia and the most likely routes that early H. Sapiens took when they arrived to that part of the world - in the last map it seems "natural" that Myanmar and Vietnam were two centers, with a third one in the now semi-insular Sundaland, i.e. Malaysia and West Indonesia)

      → http://forwhattheywereweare.blogspot.com/search/label/Eurasian%20colonization (for all kind of entries relative to the colonization of Eurasia+ or rather Asia+, just browse and pick what you like, if anything at all)

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  2. I am an indian from Burma; I get most of these; I was just confused about Bamars going to Vietnam. Our understanding is that Bamars got sstuck in the central burma and Lower Irawaddy. If anything, Vietnam and Mynmar are separated by multiple mountain ranges and river valleys.

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