DNA results from Rakhigarhi are now being reported (really!)

It looks like Outlook India is the first out of the gates to start reporting on the results from Rakhigarhi in northwest India, We Are All Harrapans. This is a “mature phase” Harrapan site that dates to about 2250 BC or so. Media reports have always been garbled on this topic, so anything that is coming not out of a paper needs to be treated cautiously. But I’ve heard some of the same things from independent sources from a while back, so I believe that this reporting is broadly on the mark.

Basically, the individual(s) they got DNA out of did not have any Eurasian steppe ancestry. This seems to confirm again that Eurasian steppe ancestry, which is found in fractions as high as ~30% in twice-born varna in Northern India (e.g., Rajputs, Tiwari Brahmins), arrived after 2000 BC. That is, after the peak period of the Indus Valley Civilization.

Again, one has to be wary of anything from the media because I’ve heard so many confusing things, including claims of garbled quotes, but here’s one of the authors of the forthcoming paper being quoted:

We did some analysis to figure out the exact date of the admixture. We have prepared a model in which all these stats fit together very tightly and that model suggests the Central Asian admixture happened about 1500-1000 BC…. Significant mixing happened around 1000 BC, also at 800 BC and 600 BC.

This is totally in line with the results from the March preprint discussed in the piece. That is, the Swat Valley samples show admixture and genetic change after 1200 BC. And the semi-historical understanding that we have of India during the period between 1000 BC and the rise of Mauryas is that it was a society in flux. But the only way the dating was changed by the Rakhigarhi results is if the genome is high enough quality that it allowed them to narrow down the parameters on some of the estimates of admixture.

One thing to keep in mind is that it is unlikely that the “Harappan people” were one single people genetically. There was probably a lot of variation in admixture with the indigenous South Asian substrate. And, I believe that the inflated steppe & AASI (“Ancient Ancestral South Indian”) ancestry you see in some North Indian Brahmin groups compared to Sindhis (who are more “Iranian”) is evidence that the Indo-Aryan intrusion resulted in an expansion of people with West Eurasian ancestry much deeper into South Asia than was the case with the Harappans.

And of the Harappans, some of the Indian scholars have asserted that their descendants are still present in the region. I think this is right, insofar as some of the jati groups, often scheduled caste, in the northwestern region of South Asia share a lot more affinity with populations to the south and east.

Related: Michael Witzel has commentary from a more linguistic perspective. If the “Para-Munda” hypothesis is right, I think what Witzel is seeing is the substrate language on which Munda was overlain, because Munda people are clearly intrusive from Southeast Asia in the period between 2000 and 1000 BC.

Addendum: If a relatively late intrusion (after 1500 BC) of Indo-Aryans to South Asia is supported by the evidence, it would be interesting in light of the high likelihood that Indo-Aryans were present in the region of upper Mesopotamia before 1500 BC. I believe that these “Indo”-Aryans actually probably never had any contact with South Asia, but descended from the horizon of cultures of which Sintashta and Andronovo were constituents. The Indo-Aryans who arrived in South Asia were probably from a different branch, and likely had interactions with other peoples in what is today eastern Iran and Afghanistan.

The peopling of the Indian subcontinent at the dawn of knowing

A few people have been pointing me to a new paper, A Bayesian phylogenetic study of the Dravidian language family, which implies that the Dravidian language family diversified ~4,500 years ago. I don’t have much to say about the paper itself since it aligns with my own conclusions, but it’s well outside of any field that I can judge (though it does use standard phylogenetic packages I’ve used).

Recently I’ve been going back to old posts of mine on South Asian population genetics because no matter how much some people drag their feet on this question, we’re pretty close to knowing how South Asians came to be. Here’s what I said in December of 2010:

Who were the Indo-Iranians? I lean toward the proposition that they do derive from the Andronovo culture of the Eurasian steppe. This would date the entrance and expansion of Indo-Aryans in northern India 3-4,000 years ago. I also contend that the dominant element of ancestry among modern South Asians is not Indo-Aryan. Rather, it is an ancient stabilized hybrid of pre-agricultural societies in the Indus valley and Neolithic farmers who originated from what is today western Iran and eastern Anatolia. Therefore, I posit that the “Aryanization” of the Indian subcontinent is properly modeled as the same processes which led to the emergence of an Anatolian and Rumelian Turkish identity; a small elite population which forces an identity shift among the majority.

Where was I wrong? Where was I right?

Even looking at ADMIXTURE plots which don’t always give an accurate sense of population history it seemed likely that “Ancestral North Indian” (ANI) was not one thing. Some South Asian populations seemed to have much stronger affinities to West Asian populations. And in particular those from highland West Asia, toward the Caucasus. These include groups in southern Pakistan, but also to some extent in South India. In contrast, other groups had affinities with Eastern European populations, in particular, high caste North Indians, and to a lesser extend Indo-European peoples more generally.

I think I got the dynamic correct. Subsequent analyses comparing ancient DNA from the Caucasus and Iran suggest that all South Asians have a lot of shared drift (ergo, ancestry) with highland West Asians, while a smaller subset has high shared drift (ergo, ancestry) with pastoralists from the Eurasian steppe. The groups match up with what the ADMIXTURE plots were suggesting.

There was more than one pulse of ANI-like ancestry and that one of them was like West Asians and one more like Europeans. Remember, this is before we knew the acronyms ANE, WHG, and EEF. Or CHG and Eastern Middle Eastern Farmers and Western Middle Eastern Farmers.

But, I think I was wrong about the magnitude of the admixture. This was before ancient DNA had revolutionized our understanding of population movement and turnover. I was still resisting the mass migration of a whole folk across huge distances. I’m more open to that now. I am not sure I still believe the very high steppe fractions implied in some of the recent analyses, but it’s certainly higher than I would have believed back then.

Finally, the recent diversification of the Dravidian languages supports the model that their current distribution is not primordial. Rather, they probably expanded relatively recently from the northwest of the subcontinent. Probably earlier than the Indo-Aryan expansion into the Gangetic plain, but not that much earlier.

Additionally, because the Dravidians were not primordial, but expanding only somewhat ahead of Indo-Aryans, they were part of an interactive social-cultural sphere with the Indo-Aryans. I think the very high frequency of R1a1a-Z93 in some non-Brahmin South Indian groups, even tribal ones, suggests to me that the expansiveness of some paternal Indo-Aryan kin networks across the whole subcontinent.

Addendum: Much of the attention goes to the ANI dynamics. But though recent work attests to the overwhelmingly diversity, and basal character, of South Asian mtDNA lineages, we can’t be entirely sure that they are indigenous without ancient DNA. If a migration from the east at the Pleistocene-Holocene boundary was characterized by gradual diffusion of groups with reasonable effective population sizes they could have brought over their diversity.