David Reich, a professor of Harvard Medical School, partnered with Indian archaeologist Vasant Shinde and other experts to study skeletal DNA from Rakhigarhi, an Indus Valley Civilisation (IVC) site. Their study, published last week in the journal ‘Cell’, has generated a debate with its new assessments on the IVC period and the extent of its imprint on modern day South Asia. Excerpts from an email interview with David Reich by ET:

Vasant Shinde, the lead author of this study, has been quoted as saying that this genetic study is evidence that there was no major Aryan invasion or mass Aryan migration into South Asia. Do you agree?

Our study finds that the single largest genetic contributor to people living in South Asia today, is people from a population of which the Indus Valley Civilisation individual we analysed was a part. Some people in South Asia have a modest, but meaningful proportion of their ancestry from people from the Steppe, north of the Black and Caspian Seas; the number ranges from 0-30%. People with this ancestry almost certainly spread into South Asia from the north 4,000-3,500 years ago.

Many people question how the genetic evidence from the IVC, which predates the Aryan phase, can establish that there was no mass migration or invasion.

I think the identification of the ancestry of people living at the time of the IVC phase in South Asia does meaningfully contribute to our understanding of what happened later. For the first time, we have a genetic model that fits statistically for most present-day South Asians: mixture of IVC-like people, and other (smaller contributions) from other populations for which we have genetic data. This allows us to be specific about what other populations contributed to present-day South Asians, and when the mix occurred.

Shinde has stated that the Vedic era followed naturally from the Harappan /Indus Valley civilisations and was not introduced by outsiders/Aryans. Would you agree?

This is an archaeological question and not one that I can comment on authoritatively as a geneticist. It is true that people, with ancestry like that of the IVC individual(s) we sequenced, were the primary source of ancestry of people in South Asia. So, it is natural to expect that they made important cultural contributions as well. Archaeologically, the material cultures of the early Vedic period have little obvious connections to those from the Steppe. So, even though there was a substantial (if quantitatively modest) genetic contribution from the north, the material cultural contribution may be hard to detect. We see something similar in some instances in the archaeological and ancient DNA record of Europe, as discussed in the final paragraphs of our ‘Science’ paper.

READ  Using Leverage Wisely in Forex Trades

“…It is striking that there are so few material culture similarities between the Central Steppe and South Asia in the Middle to Late Bronze Age (i.e., after the middle of the second millennium BCE). Indeed, the material culture differences are so substantial that some archaeologists report no evidence of a connection. However, lack of material culture connections does not provide evidence against spread of genes, as has been demonstrated in the case of the Beaker Complex, which originated largely in western Europe but in Central Europe was associated with skeletons that harbored ~50% ancestry related to Yamnaya Steppe pastoralists (20). Thus, in Europe we have an unambiguous example of people with ancestry from the Steppe making profound demographic impacts on the regions into which they spread while adopting important aspects of local material culture. Our findings document a similar phenomenon in South Asia, with the locally acculturated population harboring up to ~20% Western_Steppe_ EMBA–derived ancestry according to our modeling (via the up to ~30% ancestry contributed by Central_Steppe_MLBA groups)”

“There are also profound differences between the Bronze Age and Neolithic spreads of ancestry across the two subcontinents. One is that the maximum proportion of peninsular hunter-gatherer ancestry is higher in South Asia (AASI ancestry of up to ~60%) than Europe (WEHG ancestry of up to ~30%) (7), which could reflect stronger ecological or cultural barriers to the spread of people in South Asia than in Europe, allowing the previously established groups more time to adapt and mix with incoming groups. A second difference is the smaller proportion of Steppe pastoralist– related ancestry in South Asia compared with Europe, its later arrival by ~500 to 1000 years, and a lower (albeit still significant) male sex bias in the admixture, factors that help to explain the continued persistence of a large fraction of non–Indo-European speakers amongst people of present-day South Asia today. The situation in South Asia is somewhat reminiscent of Mediterranean Europe, where the proportion of Steppe ancestry is considerably lower than that of Northern and Central Europe (Fig. 3) and where many non–Indo-European languages are attested in classical times (67).”

READ  Betting big on corporate banks: Prashant Jain, HDFC Mutual Fund

Do the findings of the study in any way indicate that the IVC is “the largest source of ancestry for South Asians” and not the Aryan civilisation?

I don’t know what the “Aryan civilisation” is; there is certainly no archaeological evidence of a civilisation north of the Black and Caspian Seas or in the Steppe in the Bronze Age that could compare in any way in complexity or cultural sophistication to the IVC. The genetic data certainly points to the IVC being “the largest source of ancestry for South Asians”.

The paper notes that the “first farmers of the fertile crescents contributed little to no ancestry to later south Asians” and farming was largely indigenously developed by the resident IVC population over successive phases. Your views.
The Mature IVC is 2600-1900 BCE, and as I understand, archaeology it’s not correct to call any South Asian culture a “civilisation” prior to ~3000 BCE for sure. Farming started many thousands of years earlier in the Indus Valley region. So, it did not arise in the IVC itself, but rather in predecessor cultures which, however, were connected culturally and plausibly genetically. I do stand by our two lines of evidence that eastward migration of farmers from the fertile crescent, via the Iranian plateau, does not seem to have been responsible for the advent of farming into South Asia.

Is there ambiguity about the transmission of Indo-European languages into South Asia and when exactly did it occur?

Our study is not ambiguous on this topic:

From the last line of the abstract of the Science paper

“The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the distinctive features shared between Indo-Iranian and Balto-Slavic languages.”

READ  Otto Warmbier's Reminder

From the penultimate paragraph of the Cell paper

“Our results also have linguistic implications. One theory for the origins of the now-widespread Indo-European languages in South Asia is the ‘‘Anatolian hypothesis,’’ which posits that the spread of these languages was propelled by movements of people from Anatolia across the Iranian plateau and into South Asia associated with the spread of farming. However, we have shown that the ancient South Asian farmers represented in the IVC Cline had negligible ancestry related to ancient Anatolian farmers as well as an Iranian-related ancestry component distinct from sampled ancient farmers and herders in Iran. Since language proxy spreads in pre-state societies are often accompanied by large-scale movements of people (Bellwood, 2013), these results argue against the model (Heggarty, 2019) of a trans-Iranian plateau route for Indo-European language spread into South Asia. However, a natural route for Indo-European languages to have spread into South Asia is from Eastern Europe via Central Asia in the first half of the 2nd millennium BCE, a chain of transmission that did occur as has been documented in detail with ancient DNA. The fact that the Steppe pastoralist ancestry in South Asia matches that in Bronze Age Eastern Europe (but not Western Europe [de Barros Damgaard et al., 2018; Narasimhan et al., 2019]) provides additional evidence for this theory, as it elegantly explains the shared distinctive features of Balto-Slavic and Indo-Iranian languages (Ringe et al., 2002).”





READ SOURCE

WHAT YOUR THOUGHTS

Please enter your comment!
Please enter your name here