In this post, I will start getting my thoughts about the seminal SC Asian paper organized in written form. I have had these stored in my head for 2 years. The data in the paper is absolutely fantastic, and we get the first aDna from South Asia ie Swat valley. But there are so many conclusions and data analysis choices made by the authors that left me scratching my head, so much so that this post got delayed because I just have so much to say but don't know where to begin.
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| Abdullah Al Ameriki on Flickr, CC BY 2.0, via Wikimedia Commons |
So without getting ahead of myself, I will only address this claim made in the paper1 (bolded emphasis is mine). I will deal with the rest of the head scratches later in some other posts.
Groups that traditionally view themselves as being of priestly status in this and the preceding panel are shown in red (“Brahmin,” “Pandit,” and “Bhumihar” but excluding “Catholic Brahmins”), and tend to have a significantly higher ratio of Central_Steppe_MLBA to Indus_Periphery_Cline ancestry than other groups.
More generally, there is a notable enrichment in groups that consider themselves to be of traditionally priestly status: 5 of the 6 groups with Z less than −4.5 were Brahmins or Bhumihars even though they comprise only 7–11% of the 140 groups analyzed (p less than 10−12 by a χ2 test assuming all the groups evolved independently).
Nevertheless, the fact that traditional custodians of liturgy in Sanskrit (Brahmins) tend to have more Steppe ancestry than is predicted by a simple ASI-ANI mixture model provides an independent line of evidence, beyond the distinctive ancestry profile shared between South Asia and Bronze Eastern Europe mirroring the shared features of Balto-Slavic and Indo-Iranian languages (59), for a Steppe origin for South Asia’s Indo-European languages prior to ~2000 BCE.
The claim is quite simple and appealing - Steppe ancestry has a special relation to brahmin groups, but not other groups and therefore another line of evidence that steppe ancestry IS CAUSAL TO THE ETHNOGENESIS OF BRAHMIN CASTE AND THEREFORE VAIDIK RELIGION.
One has to look deep at the supplementary information in the paper to find out flaws in this data. I'll call them 'NOT SO MAJOR FLAWS' and will discuss them a bit later. But before that, I want to point out a basic problem with this whole approach. Which is
CORRELATION DOES NOT IMPLY CAUSATION, AND THE RESEARCHER'S CONFIRMATION BIAS NEEDS TO BE CHECKED
This is one of the MAJOR FLAWS of the authors' claim I am discussing. The steppe ancestry of modern Brahmins cannot tell us that the ancient steppe ancestors (males as claimed in the paper) married the ancestors of these soon-to-be Brahmins and Bhumihars of UP, Bihar, and Nepal, and because of this admixture the Brahmin caste was born. These steppe males also brought the proto Sanskrit language apparently. That is just a conjecture at this point.
I'll posit another scenario as to why this Steppe/IndusPeriphery ratio is high in these UP Bihar area modern brahmins. It is this
The high social status of Brahmins over the centuries allowed them plenty of choice in marriage, and they were able to marry women with higher West Eurasian and steppe ancestry.
My reasoning is backed up by this 2016 paper2 about Uttarakhand castes.
When comparing with the previous analyses, our data showed significant (unpaired t-test P<0.0001) higher proportion of West Eurasian-specific lineages among traditionally higher caste (Brahmin and Kshatriya) populations for maternal lineages, although it was non-significant for the paternal ancestry (unpaired t-test P=0.5468).
The paper is basically saying that west Eurasian (Iranian, SC Asian, and steppe) ancestry in modern Uttarakhand brahmins and Kshatriyas is mediated through women. This is exactly the conclusion made by Narasimhan from the study of the Swat valley data as well.
THE NOT SO MAJOR FLAWS
The authors completely fail to mention the Brahmin groups which do not have an extreme z score for the Steppe/Indus Periphery Ratio. Looking into the supplementary file of the paper which has Tables 1-5 in excel format, there are several brahmin groups with non-significant z scores. What about them?
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| Filtered brahmin data list from table S5 from the supplement. AHG = Onge Andamanese |
As you can see, none of the steppe/Indus Periphery ratio of the Brahmin shaded populations is significant (<-3). Why is this fact not mentioned? the data is taken straight from the supplement, none of the analysis in the above table is my own. I have only filtered the list and shaded the populations.
THE BIGGEST FLAW
What does Steppe/IndusPeriphery ratio even mean?? It would have meant something important if the model for modern Brahmins was just Steppe + Indus Periphery. But as you can see from the above table, it's Onge + Steppe + Indus Periphery. And there is no pure Onge-like population to be found in India around 2nd mill BCE. So this 3-way model is not a proximal model. Why assume that locals in Punjab and locals in Bihar would have the same amount of Onge component as each other before steppe ancestry came in? Surely there was more Onge component in the east. Then why is it considered separately? Just to get a good steppe/Indus periphery ratio for Brahmins?
Let me try to explain with an example.
Suppose a Khatri man lived in Punjab, and a Brahmin man lived in Bihar around 1000bce.
The ancestry of Khatri man is 100% Indus Periphery and 0% Onge.
The Bihari Brahmin being eastern has more Onge - So 75% Indus periphery and 25% Onge related.
Now suppose that 2 steppe women migrate and each marries one of the 2 respectively. The couples have 1 child each. What will be the % of the three components in both children? The table below shows the ancestries of the children.
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| See how we can create a high Steppe/IndusPeriphery ratio in eastern Indian Brahmins. |
Voila!! We created a high Steppe/Indus periphery ratio in one of the two even though they had the same external steppe input. Hence proved, this Steppe/IndusPeriphery ratio means nothing for a 3 source model. The paper has many such head-scratchers, I shall continue at another time.
1 Narasimhan VM, Patterson N, Moorjani P, et al. The formation of human populations in South and Central Asia. Science. 2019;365(6457):eaat7487. doi:10.1126/science.aat7487
2 Negi, N., Tamang, R., Pande, V. et al. The paternal ancestry of Uttarakhand does not imitate the classical caste system of India. J Hum Genet 61, 167–172 (2016). https://doi.org/10.1038/jhg.2015.121
Also, read
Vote closed:)
20 comments:
Excellent criticism with respect to the three-way admixture modelling.
I have a comment on the distribution of the Steppes components within India -
“The strongest two signals were in Brahmin_Tiwari (Z = −7.9) and Bhumihar_Bihar (Z = −7.0).”
Narasimhan fails to explain to the reader as to why Bhumihars and Tiwaris (among all castes of Brahmins) exhibit this peaking of the Steppes component. What historical episode caused this? A Western reader who doesn’t know the geographical and historical distribution of Brahmins might be inclined to fly with it.
The two states with the highest proportions of Brahmins as a percentage of their populations are Uttarakhand (22%) and Himachal Pradesh (18%). Within Hindu traditional stories, they are frequently referred to as Dev-Bhoomi (Land of the Gods). A logical expectation is a geographical convergence of the “Steppes-peak” castes and the distribution of Brahmin percentages within a region’s population. Remember, Uttarakhand is twice the area of Belgium!!
Instead the peak occurs in the Gangetic plains only - places that were the stomping grounds for some of the most gargantuan empires (Magadh) that the world has witnessed in any era. The Steppes component peaking in these two Gangetic castes (specific geographical area) indicates that there might have been another reinforcement mechanism at work. Perhaps the result of foreign elites assimilated into Empire. It is upto the reader to reflect on the coincidence of the geographical locus of past Indian Empires and the Steppes peak in modern Indians.
excellent points Bruin, indeed uttarakhand, UP are the most visited pilgrimage regions as well.
Maybe increased contact with the steppes post Buddha due to pilgrimage from steppe to Buddha's hometown, who knows lol.
I think all the attested invasions of India since the early first millennium BCE contributed to strengthening of the Steppes component among Indian elites - Yonas, Yavanas, Hunas, Kidarites, Sakas, Achaeminids.
For example, Samudragupta, the greatest of the Gupta kings, of the Allahabad Pillar fame, where the Iranian Shahanushahi pay him tribute - he had a wife named Datta Devi. The name literally means "tribute" - a defeated king from India's Northwest gave his daughter to cement an alliance.
A bit earlier in the textual tradition - the 100 Kauravas were sons of Gandhari - again from the North West. This lore must have some basis in reality - not that a single mother could have produced a 100 sons - but as an allusion to the perceived foreignness of the pretenders to the throne. Does this not sound familiar even in today's politics?
Even within a multidisciplinary approach - we see geneticists claiming a single massive Steppes influx but there is no archaeological record (Kenoyer, Shinde, Possehl, BB Lal). On the other hand, we see very good material evidence of the intrusion of Yonas, Yavanas, Hunas, Kidarites, Sakas, Achaeminids into India. Are we to believe that they contributed nothing to modern Indian genetics??
I have no doubt that the Steppes component is the reinforced result of successive waves of enrichment - specifically related to empires (invasion and not migration).
Even a victorious Saka king gave his daughter to a defeated brahmin kings son, for politics and peace.
The inscription relating the marriage between Rudradāman's daughter and Vashishtiputra Satakarni appears in a cave at Kanheri:
"Of the queen ... of the illustrious Satakarni Vasishthiputra, descended from the race of Karddamaka kings, (and) daughter of the Mahakshatrapa Ru(dra)....... .........of the confidential minister Sateraka, a water-cistern, the meritorious gift.
— Kanheri inscription of Rudradaman I's daughter".
The best evidence for an unalloyed and realistic commentary on marriages between locals and foreigners comes from no other than Chanakya himself. In no less than six sections - he lays out the dangers of marrying foreign women or intrigue with foreign women. Repeatedly cautions about picking a woman for her character and intelligence and not for her looks.
While this seems misogynistic and prudish, an analysis of his other sections reveals pragmatism and level headed advice. One cannot speculate but it is somewhat evident that Chanakya is reacting to a running or ongoing trend in society. Mail-order brides in the 4th century BCE!!
very interesting, didnt know this.
Hi, regarding the low-ish absolute value of Z ratio in south indian brahmins or among haryanvi brahmins, is it possible due to intermarriage(anuloma vivah during dire times) with local groups who were more enriched in InPe ancestry. Razib and narasimhan talked about in case of tamil brahmins where they said their low-ish Steppe/InPe ratio was because of admixture with some reddy like population.
In case of Kashmiri pundits, from whatever I can recall, I read a thread on twitter regarding KPs being 'forced' to break endogamy under muslim rule there in kashmir, will try to get the thread.
If steppe ancestry in gangetic plains brahmins is indeed from female side, then that must be visible in case of gangetic plains brahmins especially bihari, nepali and east UP brahmins. Do we have data for these groups instead of extrapolating from uttarakhand and himachali brahmins study ?
"The two states with the highest proportions of Brahmins as a percentage of their populations are Uttarakhand (22%) and Himachal Pradesh (18%). Within Hindu traditional stories, they are frequently referred to as Dev-Bhoomi (Land of the Gods)" --- Hi, it's highly possible that many of the Uttrakhand brahmins especially the kumaoni ones are of khasa origins.
"Perhaps the result of foreign elites assimilated into Empire. It is upto the reader to reflect on the coincidence of the geographical locus of past Indian Empires and the Steppes peak in modern Indians." ---
Hi Bruin,
What are your thoughts on the admixture dates between "west eurasian" and "east eurasian" ancestries given by ALDER for the above castes ? For Brahmin_Tiwari, it was 105 +- 9 generations ago which using generation time of 28 years, gave a mean date of 984BCE with 95% confidence interval between 1467 BCE - 501 BCE.
For Bhumihar Bihar, it's relatively recent with admixture around 95 +- 16 generations ago i.e., 714 BCE with 95% confidence interval between 1612 BCE - 200 CE.
@tim
"Razib and narasimhan talked about in case of tamil brahmins where they said their low-ish Steppe/InPe ratio was because of admixture with some reddy like population."
Sure, in the same way, i propose that UP brahmins admixed with a steppe like population later.
" Do we have data for these groups instead of extrapolating from uttarakhand and himachali brahmins study ?"
Uttarakhand was part of UttarPradesh till 2 decades back, hadnt become a new state then.
the ALDER admixture dates are useless because of the super wide error margins
@Bruin @vAsiSTha
the historian Vedveer Arya dates the first Scythian intrusions in India to around 700-600 BCE. Is there evidence of steppe genetic components intruding around this time too?
"Sure, in the same way, i propose that UP brahmins admixed with a steppe like population later."
Yes, that may be possible and I recall Niraj Rai claiming in an interview that they see Steppe_MLBA ancestry in Gangetic plains quite late, he claimed that admixture would have started somewhere around 800 BCE - 700 BCE. However, assuming the claim of brahmins getting their steppe ancestry solely via women is true, I have a few questions .
(i) How would we explain the case of other gangetic castes (rajputs, ahirs/yadavs etc. who have decent steppe ancestry though less than brahmins) ? Is their steppe also women mediated ?
(ii) Do you think that steppe_MLBA ancestry obtained using current models is inflated due to some pre-existing WSHG rich ancestry that is giving overestimates at the moment as some people think ?
(iii) Do you think that the high steppe in other groups like Rors and Jats is also mediated through females ? The pathak et al paper on NW indian groups listed 37.5% of mtDNA HGs in Rors as 'West Eurasian' however, out of those, nearly 7.7% were U7 and 7.7% were W, neither of which can be considered as bronze age steppe haplogroups.
"Uttarakhand was part of UttarPradesh till 2 decades back, hadnt become a new state then" --- Yes, correct me if I am wrong but historically there were different sub-cultural zones, i.e., the bhojpuria, maithili culture in east UP and north Bihar , and garhwali and kumaoni cultures in the himalayas.
@3rdacc difficult to say without aDna from the time, but I'm sure there will be some
"However, assuming the claim of brahmins getting their steppe ancestry solely via women is true"
This is not my claim. My claim currently till we get new data is that the R1a which is L657 cannot be considered mediated through steppe males.
"(i) How would we explain the case of other gangetic castes (rajputs, ahirs/yadavs etc. who have decent steppe ancestry though less than brahmins) ? Is their steppe also women mediated ?"
Some it it sure. Check steppe and west european related mtDna in these castes, i havent studied it but 10-15% will be there.
"(ii) Do you think that steppe_MLBA ancestry obtained using current models is inflated due to some pre-existing WSHG rich ancestry that is giving overestimates at the moment as some people think ?"
yes for swat aDna. wshg/tarim_emba is required on top of sintashta. so something like dali_mlba. cant say for modern indians.
"(iii) Do you think that the high steppe in other groups like Rors and Jats is also mediated through females ? "
I believe these groups have other Z93 downstream hg like Z2124 Z2125 etc, so we can see some male mediation.
Would love to see a few posts on the relationship between maykop and yamnaya populations, or the lack there of
Will do
Regarding Z2124 in jats and rors, now while there's no formal peer-reviewed published study which has done this, a friend of mine has data on jats aggregated from various private testing sites and according to him, most(nearly all) of the jats R1a is of L657 type
thanks for the info @tim
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