Perhaps the Indus Valley Civilization did descend from Zagrosian farmers?

On the limits of fitting complex models of population history to f-statistics:

These results show that at least with regard to the AG analysis, a key historical conclusion of the study (that the predominant genetic component in the Indus Periphery lineage diverged from the Iranian clade prior to the date of the Ganj Dareh Neolithic group at ca. 10 kya and thus prior to the arrival of West Asian crops and Anatolian genetics in Iran) depends on the parsimony assumption, but the
preference for three admixture events instead of four is hard to justify based on archaeological or other arguments.

Why did the Shinde et al. 2019 AG analysis find support for the IP Iranian-related lineage being the first to split, while our findGraphs analysis did not? The Shinde et al. 2019 study sought to carry out a systematic exploration of the AG space in the same spirit as findGraphs—one of only a few papers in the literature where there has been an attempt to do so—and thus this qualitative difference in findings is notable. We hypothesize that the inconsistency reflects the fact that the deeply-diverging WSHG-related ancestry (Narasimhan et al. 2019) present in the IP genetic grouping at a level of ca. 10% was not taken into account explicitly neither in the AG analysis nor in the admixture-corrected f4-symmetry tests also reported in Shinde et al. (2019).

Cousin marriage in Bangladesh

This piece arguing for the end to cousin marriage in the UK in The Times (driven by Pakistanis) took me to a paper in PLOS One, Genetic and reproductive consequences of consanguineous marriage in Bangladesh:

The mean prevalence of CM in our studied population was 6.64%. Gross fertility was higher among CM families, as compared to the non-CM families (p < 0.05). The rate of under-5 child (U5) mortality was significantly higher among CM families (16.6%) in comparison with the non-CM families (5.8%) (p < 0.01). We observed a persuasive rise of abortion/miscarriage and U5 mortality rates with the increasing level of inbreeding. The value of lethal equivalents per gamete found elevated for autosomal inheritances as compared to sex-linked inheritance. CM was associated with the incidence of several single-gene and multifactorial diseases, and congenital malformations, including bronchial asthma, hearing defect, heart diseases, sickle cell anemia (p < 0.05). The general attitude and perception toward CM were rather indifferent, and very few people were concerned about its genetic burden.

A rate around 5% is in line with my intuition and what I’ve seen elsewhere, though there is wide variance by locality. The best thing about the paper is the chart above, the offspring of first cousin marriage have mortality rates 3 times greater than non-cousin marriages. There are other numbers relating to disease, etc. The paper is good because it’s from a developing country without world-class healthcare (though no longer a total basketcase) so you can see disease risk plainly.

More generally in relation to “cousin marriage”

– I have seen “outbred” Pakistani genomes that look like the product of cousin marriage due to the practice’s frequently earlier on in the pedigree

– This is comparable to some Indian caste groups that practice exogamy (North Indian) on the jati level. The jati has been endogamous so long that everyone has become a second cousin…

Merry Christmas!

I got a sample from someone where one parent was a West Bengal Sadgop, and another parent a Baidya with family origins in East Bengal. One hypothesis that I’ve see is that Baidya are basically Brahmins who lost their caste. Genetically this does not seem to be the case. Bengali Brahmins shift considerably toward the steppe samples compared to average Bangladeshis, and this individual does not. Rather, their uniqueness is that they have very little East Asian ancestry compared to the median. This is typical of non-Bramin West Bengalis. It is plausible to me that this individual’s Baidya parent, from East Bengal (Bangal), had more East Asian ancestry than their West Bengali (Ghoti) parent, so you see an average.

Though there are some exceptions, it seems that the non-Brahmnin bhadralok castes did undergo ritual uplift from that of conventional peasant cultivators at some point in Bengal. This seems similar with regard to Kayasthas in UP, but not in Maharashtra, where CKPs seem to have an affinity with Brahmins distinct from the Maratha cultivators.

Update: I found a preprint that pretty much answers all the questions re: Bengalis.

Here is a panel with a UMAP representation of genetic distance, and you see West Bengal is adjacent to Bangladesh. But there is a “tail” of individuals that are parallel to South Indians.

This UMAP makes clear Bengali Brahmins are distinct from Kayasthas and Sadgop. These populations seem roughly similar to most Bangladeshis except they are shift over, and I assume this means less East Asian ancestry, as PCA seems to how:

First AASI mtDNA genomes from Sri Lanka (2500 and 5500 BC)

The mitochondrial genomes of two Pre-historic Hunter Gatherers in Sri Lanka:

Sri Lanka is an island in the Indian Ocean connected by the sea routes of the Western and Eastern worlds. Although settlements of anatomically modern humans date back to 48,000 years, to date there is no genetic information on pre-historic individuals in Sri Lanka. We report here the first complete mitochondrial sequences for Mesolithic hunter-gatherers from two cave sites. The mitochondrial haplogroups of pre-historic individuals were M18a and M35a. Pre-historic mitochondrial lineage M18a was found at a low prevalence among Sinhalese, Sri Lankan Tamils, and Sri Lankan Indian Tamil in the Sri Lankan population, whereas M35a lineage was observed across all Sri Lankan populations with a comparatively higher frequency among the Sinhalese. Both haplogroups are Indian derived and observed in the South Asian region and rarely outside the region.

No idea why this comes out of Sri Lanka first, and not India (bigger country), but it is what it is.

The Todas are more like IVC people than anyone else

I noticed something interesting a few weeks ago in the supplements of the Genomes Asian 1000K paper. Look at where the Toda are on the PCA.

Now look at the Indus Valley samples I have….

I don’t have access to the Toda samples. But there’s a lot of evidence that this is a very unique population that resembles the IVC population in having less AASI but not too much (if any) steppe.

The varieties of Brahmins (and others)

Sometimes people pass me data. Turns out Rajasthani Brahmins are quite different from UP Brahmins (more northwest-shifted). In this, they are like Pandits. In contrast, Bihar Babhans are just like UP Brahmins, who don’t seem to have much structure. Gujarati Brahmins are between South Indian Brahmins and North Indian Brahmins, and closer to the latter, while Maharashtra Brahmins seem more like South Indian Brahmins.

Adivasis are just like everyone else…sort of…but not

My previous post on Adivasis was not totally clear. So I’m going to try in shorter fragments and outline things so I’m more clear. I am not 100% correct with the model below (we’ll know more later), but this is my best current conception.

  1. 10,000 BC, end of the Ice Age, NW quadrant of the Indian subcontinent inhabited by a West Eurasian associated hunter-gatherers, related to the hunter-gatherers of the Zagros mountains in Iran, with some Siberian ancestry. The other three quadrants are dominated by hunter-gatherers with deep (40,000 years diverged)  associations with East Eurasians and Australo-Melanesians. These “Ancient Ancestral South Indians” (AASI) seem to have separated from the Andaman Islanders (AI) more than 30-35,000 years ago, but the AI are their closest current relatives (AI-related populations were dominant in mainland Southeast Asia until 4,000 years ago, when rice farmers from southern China migrated into the region).
  2. Between 7,000 and 4,000 years ago extensive admixture occurred within the IVC zone in the NW between the IVC-Iranian-related population and AASI groups moving northwest. The resultant population was far more Iranian-related than AASI (say 10-20% AASI), and these people eventually became the “Indus Valley Civilization.
  3. To the south and east the AASI populations probably did experience reciprocal gene flow at the same time, as Iranian-related populations spread south and east
  4. Why this distinction? I believe during the late Pleistocene the Thar desert was larger and more forbidding and blocked gene flow between the easternmost West Eurasians and westernmost East Eurasians.
  5. Steppe ancestry likely does not show up until after 2000 BC.
  6. I believe there was a Dravidian language spoken in Sindh, and later Gujarat and Maharashtra. These populations spread southward before and after 2000 BC, and eventually, they mixed with all the AASI groups in the same.
  7. In the period between 2000 and 1 BC there is more and more mixing and the arrival of steppe populations that become culturally ascendant across the subcontinent. In the south, the Dravidian-speaking zone, there is a distinction between post-IVC populations that engage with the expanding Indo-Aryans and those that do not engage with the Indo-Aryans

The period between 2000 and 1 BC is essential. In some areas, like the NW, large numbers of steppe people settled, and imposed their language and culture, albeit in synthesis with the local populations, who would be mostly IVC. While the IVC seems to have expanded only gingerly into the upper Gangetic plain and Gujarat, the Indo-Aryans pushed into the eastern zones, and parts of the south. The fact that Adivasi in the south have the canonically Indo-Aryan R1a-Z93 indicates that young bands of Indo-Aryan men penetrated all across the subcontinent. Their genetic imprint is clear in non-Brahmin southern groups like the Reddys, so they were ubiquitous.

But it is culture that matters more. The synthesis that developed in Punjab and Upper Gangetic plain eventually spread across the whole subcontinent and explains why Sangam literature has Sanskrit loanwords. The distinction between Adivasi and caste Hindu emerges from the distance to the expanding proto-Hindu culture based on a core of Aryan culture with indigenous accretions. This was a diverse religious and cultural matrix, but there were broad family similarities, and again, the Sangam literature alludes to “brahmins,” indicating that there was an early penetration of Aryan ritualists in the south. The Adivasi emerges not as a relict or the remnant of an early population, but as a set of societies at one of the spectra of the Aryan-indigenous synthesis that characterized the subcontinent.

The Aryan can become an Adivasi, as is attested by the Aryan men who clearly integrated themselves into those communities and lost their cultural distinctiveness. Similarly, Adivasis can become caste Hindus by adopting the norms of caste Hindus.

Bangladesh and West Bengal genetics

I got a few more samples with provenance. The Bengali Brahmins are shifte the way you would expect. The Bangladesh Kayastha (someone from a Hindu background) is in the cluster with generic Bangladeshis from Dhaka. The West Bengali Kayastha is far less East Asian. My current model right now is that the Kayasthas are basically peasants that engaged in uplift, as in general they don’t seem so genetically distinct from other Bengalis, in contrast with Brahmmins. Though Bengali Brahmins do exhibit admixture with Bengalis with East Asian ancestry, they are very different overall.

Brown Pundits