Over at Brown Pundits I’ve mentioned the continuing simmer of controversy over a recent piece, How genetics is settling the Aryan migration debate. This has prompted responses in the Indian media from a Hindu nationalist perspective. One of these notes that the author of the piece above cites me, and then goes on to observe I was fired from The New York Times a few years ago due to accusations of racism (also, there is the implication that I’m just a blogger and we should trust researchers with credibility like Gyaneshwer Chaubey; well, perhaps he should know that Gyaneshwer Chaubey considers me “unbiased” according to an email exchange which I had with him last week [we all have biases, so I think he’s wrong in a literal sense]).
I was a little surprised that a right-wing magazine would lend legitimacy to the slanders of social justice warriors, but this is the world we live in. Those who believe that everything written about me in the media, I invite you to submit your name and background to me. I have contacts in the media and can get things written if I so choose. Watch me write something which is mostly fact, but can easily be misinterpreted by those who Google you, and watch how much you value the objective “truth-telling” power of the press all of a sudden.
There’s a reason so many of us detest vast swaths of the media, though to be fair we the public give people who don’t make much money a great deal of power to engage in propaganda. Should we be surprised they sensationalize and misrepresent with no guilt or shame? I have seen most of those who snipe at me in the comments disappear once I tell them that I know what their real identity is. Most humans are cowards. I have put some evidence into the public record to suggest that I’m not.
Perhaps more strange for me is that the above piece was passed around favorably by Sanjeev Sanyal, who I was on friendly terms with (we had dinner & drinks in Brooklyn a few years back). I asked him about the slander in the piece and he unfollowed me on Twitter (a friend of Hindu nationalist bent asked Sanjeev on Facebook about the articles’ attack on me, but the comment was deleted). It shows how strongly people feel about these issues.
I’m in a weird position because I’m brown and have a deep interest in Indian history. But that interest in Indian history isn’t because I’m brown, I’m pretty interested in all the major zones of the Old World Oikoumene. Aside from some jocular R1a1a chauvinism I don’t have much investment personally (I just told said Hindu nationalist friend who turns out to be R2 to clean my latrine; joking of course, though I’m sure he resents that I’m descended on the direct paternal line from the All-Father & Lord of the Steppes and he is not!).
In the aughts I accepted the model outlined in 2006’s The Genetic Heritage of the Earliest Settlers Persists Both in Indian Tribal and Caste Populations. But to be frank it always struck me as a little confusing because the tentative autosomal data we had suggested that many South Asians were closer to West Eurasians than deep divergences dating to the Last Glacial Maximum would suggest. Since I’ve written something like 5 million words in 15 years, I actually can check if I’m remembering correctly. So here’s a post from 2008 where I express reservations of the idea of long term deep heritage of Indians separate from other West Eurasians. The reason I was so impressed by 2009’s Reconstructing Indian Population History is that it resolved the paradox of South Asian genetic relatedness.
To recap, Reich et al. proposed that modern Indians (South Asians) could be modeled as a two way mixture between two distinct populations with separate evolutionary genetic histories, Ancestral North Indians and Ancestral South Indians (ANI and ASI). How distinct? ANI were basically another West Eurasian population, while ASI was likely nested in the clade with Eastern Non-Africans. Additionally, there was a NW-to-SE and caste admixture cline. In other words, the higher you were on the caste ladder the more ANI you had, and the closer your ancestors were from the north and west, and more ANI you had. The difference between Y and mtDNA, male and female, could be explained by sex-biased migration.
But there were still aspects of the paper which I had reservations about. After all, it was a model.
- Models are imperfect fits onto reality. The idea of mass migration seemed ridiculous to me at the time, because even by the time of the Classical Greeks it was noted that India was reputedly the most populous land in the world (to their knowledge). But ancient DNA has convinced me of the reality of mass migrations.
- I wasn’t sure about the nature of the closest modern populations to the ANI. The researchers themselves (in particular, Nick Patterson) told me that the relatedness of ANI to Europeans was very close (on the order of intra-European differences). But modern Indians do not look to be descended from a population that is half Northern European physically. Again, ancient DNA has shown that there was lots of population turnover, and it turns out that Europeans and ANI were likely both compounds and mixed daughter populations of common ancestors (also, typical European physical appearance seems to have emerged in situ over the past 5,000 years).
- The two way admixture modeled seemed too simple. I had run some data and it struck me that North Indian populations like Jats had something different than South Indian groups like Pulayars. In 2013 Priya Moorjani’s paper pretty much confirmed that it was more than a two way admixture along the ANI-ASI cline.
This March BMC Evolution Biology published Silva et al’s A genetic chronology for the Indian Subcontinent points to heavily sex-biased dispersals. It has made a huge splash in India, arguably triggering the write up in The Hindu. But for me it was a bit ho-hum. If you read my 2008 post it is pretty clear that I suspected the most general of the findings in this paper at least 10 years back. It is nice to get confirmation of what you suspect, but I’m more interested to be surprised by something novel.
Nevertheless A genetic chronology for the Indian Subcontinent points to heavily sex-biased dispersals has come in for lots of repeated attack in the right-wing Indian press. This is unfair, because it is a rather good paper. I suspect that it wasn’t published in a higher ranked journal because most scientists don’t consider the history of India to be that important, and they didn’t really apply new methods, as opposed to bringing a bunch of data and methods together (in contrast, the 2009 Reich et al. paper was one of the first publications which showed how to utilize “ghost populations” in explicit phylogenetic models with relevance to human demographic history).
As it happens I will be writing up my thoughts in detail in an article for a major Indian publication (similar circulation numbers as The Hindu). This has been in talks for over six months, but I’ve been busy. But a month or so ago I thought it was time that I put something into print for the Indian audience, because I felt there was some misrepresentation going on (i.e., the Aryan invasion theory has not been been refuted by genetics, but this is what many Indians assert).
For any years people have told me there are certain topics that shouldn’t be talked about. I have offended people greatly. There are many things people do not want to know. I have come to the conclusion this is not an entirely indefensible viewpoint (though if you accept this viewpoint, I think acceptance of authoritarianism is inevitable, so I hope people will toe the line when the new order arrives; knowing their personalities I think they will conform fine). But my nature is such that I continue to have nothing but contempt for the duplicitous and craven manner in which people go about these sorts of private conversations. I assume that as someone with the name “Razib Khan” I will be attacked vociferously by Hindu nationalists, who will no doubt make recourse to the Left-wing hit pieces against me to undermine my credibility. The fact that these groups are fellow travelers should tell us something, though I will leave that as an exercise for the reader.
I will write my piece that reflects the science as I believe it is, without much consideration of the attacks. That is rather easy for me to do in part because I live in the United States, where denigrating the deeply held views and self-esteem of Hindu nationalists is not sensitive or politically protected (unlike say, Muslims). And Hindu nationalists are less likely to kill me by orders of magnitude than Muslim radicals, and they have far less purchase in this nation then the latter (though you may be interested to know that very conservative Muslims follow me on Twitter; they’re actually more open-minded than many SJWs to be entirely honest).
Let me go over some general points that I see coming up over and over on the relationship between Indian (pre)history and genetics in the critiques .
One of the major critiques has to do with the nature of R1a-Z93 and its subclades. Basically this Y chromosomal haplogroup, the greatest that has ever been known, exhibits a strong signature of very rapid expansion over the past 4,000 years or so. It is divided from Z282. While Z93 is found in South Asia, Central Asia, and Siberia, Z282 is European, with its dominant subclade the one associated with Eastern Europeans. Both of these clades of R1a have gone through massive expansion. In the Altai region R1a is 40% of the heritage of peoples who are now predominantly East Eurasian today. But they are Z93. Additionally, ancient DNA from the Pontic Steppe dated ~4,000 years ago from Srubna remains is Z93, as are Scythian remains from the Iron Age.
Much of the argument comes down to dating, and citing papers that give deep coalescence numbers between difference branches of R1a1a. Hindu nationalists and their fellow travelers point to recent papers which give dates >10,000 years ago, and so place the origin of Z93 plausibly in the Pleistocene. The problem is that Y chromosomal coalescence dating is something of a mug’s game. Often they use microsatellite data whose mutational rates are highly uncertain. In contrast, using SNP data, which has a slower mutation rate but requires a lot more data, you get TRMCA (common ancestry) between Z93 and Z282 around ~5,800 years ago. But coalescence estimates often have wide confidence intervals of thousands of years. And even with these intervals, the assumptions you make (e.g., mutation rate) strongly influence your midpoint estimate.
The Y chromosomal data is powerful, but its interpretation is still buttressed upon other assumptions. The really big picture framework is the nature of ancient genome-wide variation across Eurasia. Lazaridis et al. 2016 condition us to a prior where much of Eurasia was subject to massive population-wide genetic changes since the Holocene. Therefore, I am much less surprised if there was massive genetic change in India relatively recently. The methods in Priya Moorjani’s paper and in other publications make it obvious that mixture was extensive in South Asia between very distinct groups until about ~2,000 years ago. In fact, Moorjani et al. using patterns of variation across the genome to come at a number of two to four thousand years ago as the period of massive admixture.
Though we don’t have relevant ancient DNA from India proper to answer any questions yet, we do have ancient DNA from across much of Europe, Central Asia, and the Near East. What they show is that Indian populations share ancestry from both Neolithic Iranians and peoples of the Pontic steppe, who flourished ~5 to ~10,000 years ago. To some extent the latter population is a daughter population of the former…which makes things complicated. Conversely, no West Eurasian population seems to harbor ancient signals of ASI ancestry.
One scientist who holds to the position that most South Asian ancestry dates to the Pleistocene argued to me that we don’t know if ancient Indian samples from the northwest won’t share even more ancestry than the Iranian Neolithic and Pontic steppe samples. In other words, ANI was part of some genetic continuum that extended to the west and north. This is possible, but I do not find it plausible.
The reasons are threefold. First, it doesn’t seem that continuous isolation-by-distance works across huge and rugged regions of Central Eurasia. Rather, there are demographic revolutions, and then relative stasis as the new social-cultural environment crystallizes. This inference I’m making from ancient DNA and extrapolating. This may be wrong, but I would bet I’m not off base here.
Second, it strikes me as implausible that there was literally apartheid between ASI and ANI populations for the whole Holocene right up until ~4,000 years before the present. That is, if Northwest India was involved in reciprocal gene flow with the rest of Eurasia over thousands of years I expect there should have been some distinctive South Asian ASI-like ancestry in the ancient DNA we have. We do not see it.
Third, one of the populations with strong affinities to some Indian populations are those of the Pontic steppe. But we know that this group itself is a compound of admixture that arose 5,000-6,000 years ago. Because of the complexity of the likely population model of ANI this is not definitive, but it seems strange to imagine that ANI could have predated one of the populations with which it was in genetic continuum as part of a quasi-panmictic deme.
Finally, many of the critiques involve evaluation of the scientific literature in this field. Unfortunately this is hard to do from the outside. Citing papers from the aughts, for example, is not wrong, but evolutionary human population genomics is such a fast moving field that even papers published a few years ago are often out of date.
Many are citing a 2012 paper by a respected group which argues for the dominant model of the aughts (marginal population movement into South Asia). One of their arguments, that Central Asian migrant should have East Asian ancestry, is a red herring since it is well known that this dates to the last ~2,000 years or so (we know more now with ancient DNA). But the second point that is more persuasive in the paper is that when they look at local ancestry of ANI vs. ASI in modern Indians, the ANI haplotypes are more diverse than West Eurasians, indicating that they are not descendants but rather antecedents (usually the direction of ancestry is from more diverse to less due to subsampling).
There are two points that I have make here. First, local ancestry analysis is difficult, so I would not be surprised if they integrated ASI regions into ANI and so elevated the diversity in that way (though they think they’ve taken care of it in the paper). Second, if the ANI are a compound of several West Eurasian groups then we expect them to be more diverse than their parents. In other words, the paper is refuting a model which is almost certainly incorrect, but the alternative hypothesis is not necessarily the true hypothesis (which is a more complex demographic model than many were testing in 2012).
But there are many things we do not know still. Many free variables which we haven’t nailed down. Here are some major points:
- Y chromosomal lineages have a correlation with ethno-linguistic groups, but the correlation is imperfect. R1b and R1a seems correlated with Indo-European groups, but both these are found in high proportions in groups which are putatively mostly “pre-Indo-European” in origin (e.g., Basques, Sardinians, and South Indian tribals and non-Brahmin Dravidian speaking groups). Also, haplogroups like I1 in Europe expand with Indo-Europeans locally, suggesting there was lots of heterogeneity in Indo-Europeans as they expanded. In other words, Indo-European expansion in relation to powerful paternal lineages did not always correlate with ethno-linguistic change.
- There are probably at minimum two Holocene intrusions from the northwest into South Asia, but this is a floor. The models that are constructed always lack power to detect more complexity. E.g., it is not impossible that there were several migrations of Indo-Europeans into South Asia which we can not distinguish genetically over a period of a few thousand years.
- If one looks over all of South Asia it may be that ASI ancestry in totality is >50% of the total genome ancestry. I don’t have a good guess of the numbers. If this is correct, perhaps most South Asian ancestors 10,000 years ago were living in South Asia (though the fertility rate are such in Pakistan that ANI ancestry is increasing right now in relative rates).
- But, this presupposes that ASI were present in South Asia in totality 10,000 years ago, rather than being migrants themselves. If ancient DNA confirms that ANI were long present in Northwest India, I hold then it is entirely likely that ASI was intrusive to South Asia! The BMC Evolutionary Biology Paper does a lot of interpretation of deep structure in haplogroup M in South Asia. I’m moderately skeptical of this. Europe may not be a good model for South Asia, but there we see lots of Pleistocene turnover.
So where does this leave us? Ancient DNA will answer a lot of questions. Pretty much all scientists I’ve talked to agree on this. My predictions, some of which I’ve made before:
- The first period of admixture is old, and dates to the founding of Mehrgarh as an agricultural settlement. The dominant ANI component dates to this period and mixture event, all across South Asia. The presence in South India is due to expansion of these farming populations.
- A second admixture event occurred with the arrival of steppe people. Those who argue for the Aryan invasion model posit 1500 BCE as the date. But these people probably were expanding in some form before this date.
- We still don’t know who the antecedents for the Indo-Aryans were. Probably they were a compound of different steppe groups, and also other populations which were mixed in (by analogy, in Europe it is obvious now that there was some mixture with the local European farmers and hunter-gatherers as Europeans expanded their frontier westward; the same probably applies for Indo-Aryans are the BMAC).