Genes, memes, and Mundas

The Munda languages of the northeastern quadrant of the Indian subcontinent are quite interesting because they are more closely related to the Austro-Asiatic languages of Southeast Asia than to the Indo-Aryan or Dravidian languages which are spoken by their neighbors. The Munda are usually classified as adivasi, which has connotations of being an ‘original inhabitant’ of the Indian subcontinent.

More concretely, the Munda have traditionally operated outside of the bounds of Sanskrit-influenced Hindu civilizations, occupying upland zones and governing themselves as tribal units, rather than being a caste population.

What the field of genetics tells us is that there are really no true aboriginal inhabitants of the Indian subcontinent in an unmixed form. That is, the vast majority of people in the Indian subcontinent have a substantial contribution of ancestry from the wave of migration out of Africa that occupied the southeast fringe of Eurasia beginning ~50-60,000 years ago. The modern adivasi generally are defined more by their social-cultural position within the landscape of Indian culture, as opposed to their long-term residence in the subcontinent.*

The term is a particular misnomer for the Munda because of the evidence that they are intrusive to the subcontinent from Southeast Asia. We have ancient DNA and archaeology which indicates that upland rice farmers, likely Austro-Asiatic, arrived in northern Vietnam ~4,000 years ago. This makes it unlikely to me that they were in India much earlier. The Y chromosomal data indicate that the paternal ancestry of the Munda derives from Southeast Asians, not the other way around.

A new genome-wide analysis of the Southeast Asian fraction of Munda ancestry suggests that it can be as high as ~30%. The paper is The genetic legacy of continental scale admixture in Indian Austroasiatic speakers:

Surrounded by speakers of Indo-European, Dravidian and Tibeto-Burman languages, around 11 million Munda (a branch of Austroasiatic language family) speakers live in the densely populated and genetically diverse South Asia. Their genetic makeup holds components characteristic of South Asians as well as Southeast Asians. The admixture time between these components has been previously estimated on the basis of archaeology, linguistics and uniparental markers. Using genome-wide genotype data of 102 Munda speakers and contextual data from South and Southeast Asia, we retrieved admixture dates between 2000–3800 years ago for different populations of Munda. The best modern proxies for the source populations for the admixture with proportions 0.29/0.71 are Lao people from Laos and Dravidian speakers from Kerala in India. The South Asian population(s), with whom the incoming Southeast Asians intermixed, had a smaller proportion of West Eurasian genetic component than contemporary proxies. Somewhat surprisingly Malaysian Peninsular tribes rather than the geographically closer Austroasiatic languages speakers like Vietnamese and Cambodians show highest sharing of IBD segments with the Munda. In addition, we affirmed that the grouping of the Munda speakers into North and South Munda based on linguistics is in concordance with genome-wide data.

The paper already came out as a preprint many months back, so I’ve already mentioned it. The big finding, to me, is that it uses genome-wide methods to estimate an admixture in the range of ~4,000 between the southern Munda Southeast Asian and South Asian ancestral components. It also confirms something that has been pretty evident for nearly ten years of genome-wide analysis of South Asian population genetics: the Munda have less West Eurasian ancestry even after you account for the Southeast Asian admixture than any mainland Indian population outside of the Tibeto-Burman fringe.

In Narasimhan et al. the authors present a model that fits the data where:

  1. The proto-Munda mix with an “Ancient Ancestral South Indian” (AASI) population that has no West Eurasian admixture in India’s northeast
  2. Then, mix more with an “Ancestral South Indian” (ASI) population that has some West Eurasian admixture

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