South Asian gene flow into Burmese and Malays?


I happen to have a data set merged from the 1000 Genomes and Estonian Biocentre which has Malays, Burmans, and other assorted Southeast Asians, East Asians, and South Asians. In light of recent posts I thought I would throw out something in relation to this data set (you can download the data here). Above you can see the populations in the data. You see Bangladeshis consistently are shifted toward Southeast Asians in comparison to other South Asians. But both Burmans and Malays exhibit some shift toward South Asians.

I ran ADMIXTURE at K = 4. Click the image for the larger file which shows the populations, but I will tell you what’s going on.

The yellow to green represent a north-south axis in East Asia. The Han sample is mostly yellow, but there is a green component in varying degrees. This almost certainly represents heterogeneity in the Han sample of north to south Chinese. The green component is nearly ~100% in some individuals from indigenous tribes in Borneo, and balanced with the yellow among peninsular Malays. It is more at a higher frequency in Cambodia than in Vietnam or Burma, indicating the older roots of Khmers and their relative insulation from later migrations of Sino-Tibetan and Tai peoples.

The red South Asian component is found in many Southeast Asians, but curious in the Burmans and Malays there is a lot of variation within the population. That indicates admixture over time that has not homogenized throughout the population.

I ran Treemix with 5 migration edges and French rooted (1000 SNP blocks out of 225,000 SNPs) and they all looked like this. Commentary I will leave to readers….

4 thoughts on “South Asian gene flow into Burmese and Malays?

  1. Various thoughts:

    Another point on this is no covariance between the yellow and orange fractions in the Burmese samples.

    That’s useful to know because, as I recall, in Nepal and Nagaland, you get people who have both higher fractions of Northeast Asian (yellow) and South Asian (orange) related ancestry than typical for Southeast Asia. So if those mediated orange into Burma, you’d expect covariance between yellow and orange.

    Thai groups would also be a good one to look at here, for point of comparison to Cambodian and Burmese. When we do Principal Coordinates analysis of Fst scores the Thai group is very much in the same overall positions as Cambodian, tilted between South Asia and Southeast Asia, without the shift of Burmese towards NE Asia and groups from China: http://imgur.com/a/3LlSY. (So there’s a puzzle how recent that is…)

    Burmese also show some noticeable reduced Fst to the Naxi and Yi groups, from upland Sichand and Yunnan, who are otherwise fairly linear with North Han Chinese in their relationships to other populations: http://imgur.com/a/fiOMF.

    Beyond having some degree of increased relatedness to Northeast Asia and North Han-like populations compared to Cambodians, it seems this is specifically most evident in relation to the populations who are likely to be closest to the early migrations of proto-Burmese speakers into Burma.

  2. Does the treemix suggest it is a South Indian type input into Burmese rather than neighbouring Bangladeshis (who on the other hand are receiving SE Asian input)?

    Have you performed any analyses to see the nature of East Asian input into Bangladeshis?

  3. @Reza, that is an interesting interpretation. Taken literally, this suggests that the admixture into Burmese and Malay are both coming from positions beyond Bangladesh and Tamil on the rough ANI-ASI cline (https://pbs.twimg.com/media/DJUbTqNU8AAezox.jpg – from with Bangladeshi and Burusho deviate towards East Asia).

    In particular the Malay position looks to take admixture from a population closer on the tree to Cambodian than to Tamil and Burmese from somewhere between Tamil->Cambodian. The Bangladeshi sample looks to be too ANI like. One possibility: This may be a composite of flow from a Cambodian like population and flow from a South Indian like population? Mostly Cambodian like->Malay, about even into Burmese.

  4. Very much out of my field, but there was the influence of predominantly southern Indian states in trade and the spread of Buddhism, culturally, the co-existence of Sanskrit and Pali as court languages. Certainly from the time of the Pyu city states.

    Would the heterogeneity of the South Asian component correlate with the late first millenium onwards? Interesting point about a composite flow from a Cambodian like population that would bring the departure point beyond Tamils.

    Re: Bengalis, the migration event seems to have come off post Cambodians. My understanding was that this admixture would have occured with the local austro-asiatic tribals, possibly some tibeto-burman groups. Is that compatible with this tree?

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