At ASHG next Monday Niraj Rai will be presenting this poster, Reconstructing the peopling of old world south Asia: From modern to ancient genomes.
South Asia was one of the first geographic regions to be peopled by modern humans after their African exodus. Today, the diverse ethnic groups of South Asia comprise an array of tribes, castes, and religious groups, who are largely endogamous and have hence developed complex, multi-layered genetic differentiation. From such a complex structure, several questions have stood out from the research of our group and others that are only beginning to be resolved using modern sequencing techniques and targeted sampling of populations and archaeological specimens. Here, for the first time we have used ancient genomics approach to understand the deep population ancestry of Indian Sub- continent. Despite the rich sources available of modern Indian populations, success from ancient DNA specimens in the subcontinent have been limited. We have successfully analysed several museum samples and fresh excavation from the different part of India which provides us a wonderful opportunity to be able to relate these modern populations genetically with those in the past and build complex models of population mixture and migration in India. Using ancient genomics data from the human remains who have lived about 4-5 thousand years before present in North West and South of India, we are trying to understand the population history of Iron age people and their genetic relation with the North West of Indians and Iranian Farmers. Furthermore, we are providing a solid Genetic evidence that substantiates archaeological and linguistic evidence for the origins of Dravidian languages and the language of the Indus valley people.
I’ll probably be trying to make sure I catch Rai at the poster. I’m most interested in the South Indian samples. If they date to more than 4,000 years before the present, it will be quite interesting.
as you know there more than those 3 now. none of the harrapan era individuals exhibit evidence of noticeable steppe drift.
What I know, and this is second hand info, is that there are 15 more InPe samples found by the Reich team, and they have enormous variation in the AASI levels. There is also ydna and mtdna which is South Asian. But I know nothing about the ANE/WSHG levels of these populations.
It seems likely that ANE/WSHG gene flow occurred into South Asia before the arrival of steppe people.
by sampling one individual you are reconstructing the phylogeny of whole populations.
That is true but we now know that the Rakhigarhi sample is so low coverage that it is practically useless.
I’m talking about more than something like PSMC. You can tune your priors even on a little data. Assume you have a population you don’t know about. You have 100 markers from one individual. That individual maps onto African populations. It doesn’t guarantee everyone else will map in the same way, but it tunes your priors.
Similarly, all InPe samples so far lack steppe ancestry. The size of the sample is small, and the quality varies, but we are getting more confident, not less.
So we have to fall back on the InPe samples. The InPe that we know so far were definitely not a homogenous group as you know it well. The question was really whether these groups lacked steppe_mlba which modern Indians have. But the paper unfortunately failed to demonstrate this conclusively.
Final conclusions are going to come down to
large sample sizes
good geographic representation
But we can make preliminary bets. It seems likely to me that the bulk of steppe_mlba arrived after 2000 BC to South Asia. Not definitive, but likely.
If you look into the Supplementary section on South Asians in the Narasimhan paper, they only use Swat_IA, Swat_H, Punjabi & Mala to represent the post Harappan South Asians. And in the various qpAdm models they generate (using 2 separate sets of outgroups), the combination with the highest p-value for both the Punjabi & the Mala involve older steppe groups beside the steppe_mlba. It is only the Swat samples that probably show steppe_mlba preference. But then again, the Swat samples show greater preference for steppe_mlba_west rather than steppe_mlba_east, which is again making no sense archaeologically.
So there are no clear answers. And to top it all, the authors implicitly assume in their qpAdm models that South Asians have to be modelled as comprising of 3 streams – steppe, Iran_N groups, AASI – to arrive at their conclusion.
the Loschbour ancient genome form luxembourg was the first mesolithic western european hunter-gatherer. *every subsequent mesolithic hunter-gatherer has been genetically very smilar*, across all of western europe. that’s because they went through a bottleneck and range expansion
But we do not know that such a range expansion took place among Harappans. And it appears that they are arguing Harappans being endogamous already and having population structure which goes against the idea of a range expansion.
This is not correct. When you undergo range expansion you will admix with the population beyond the frontier. This will produce dilution (or not, depending on population densities).
At any rate, the 2 scenarios are different, we are comparing a hunter gatherer society with a complex Bronze Age urbanised society. In Harappan times, if there was a range expansion, it was likely to be more among the less developed populations in Inner India or among the Harappans it is more likely to be restricted to the elites.
when i say *steppe* i’m talking specifically of the genetic element that is Yamnaya+EEF, which is the distinctive european back-migration into the steppe after the corded ware western migration. this component probably has added iranian farmer+ANE/WSHG in some fractions.
Though I was initially reluctant to accept this – it appears that the more steppe rich South Asian groups also have slightly more ANF/EEF. The Daamgard et al paper argued that these Northern groups also have CHG which is lacking in others. One may argue that this could only come from steppe_mlba. But then the Harappans were already interacting with Iranians, Central Asians and the Mesopotamians and probably the Caucasus groups as well. This could very well have brought in ANF and CHG in their genetic mix and we do not need to resort to a steppe_mlba explanation for it especially as the archaeological evidence is quite lacking.
otoh the incoming group could have been heterogeneous with non-steppe lineages ‘hitchhiking’. this seems to have occurred in europe: haplogroup I1 shows a star-phylogeny just like r1b and r1a. i’m pretty sure it was integrated into the indo-european expansion after cultural and biological assimilation.
Could be. Or it maybe that the reality of things were very different from how it is being interpreted.
perhaps r1a1a-z93 isn’t connected to indo-aryans necessarily, though it is sufficiently
I think that the Harappans, East Iranians and Central Asians were already IE. So even if R1a z93 expanded locally, considering how Poznick et al dated the South Asian z93 to between 2500 – 2000 BC, it is more likely, in my opinion, to be related to Indo-Aryan expansion. Nothing else that we know of historically can explain the widespread South Asian presence of this Bronze Age lineage.
But this would ofcourse mean that the steppe_mlba also received R1a Z93 from South Asia. At present state of our knowledge, there is no evidence so far to support such a claim unless we can show some sort of admixture in steppe_mlba from Harappans or BMAC or Shahr I Sokhta.
It is possible for Harappans to have been IE and not Indo-Aryan. I am skeptical of this scenario, but it’s not impossible. Indo-Aryan is clearly related to Indo-Iranian cultures which came out of the Eurasian steppe.