Most people in South Asia speak one of two varieties of language, Indo-Aryan and Dravidian. These two are not particularly closely related. Indo-Aryan is an Indo-European language, as is evident in the plethora of obvious cognates with other Indo-European dialects. I have a minimal fluency in Bengali, the easternmost of the Indo-European languages, and quite a bit more fluency with English, one of the most westernmost, and it was evident to me rather early on (e.g., grass vs. gash, man vs. manush, nose vs. nak). In contrast to me Dravidian languages are peculiar because the accent and cadence are clearly South Asian, but they are utterly impenetrable (though there are many loan words into Indo-Aryan from Dravidian).
If you have not read my post “To the antipode of Asia”, this might be a good time to do so if you are unfamiliar with the history, prehistory, and ethnography of mainland Southeast Asia. In this post I will focus on mainland Southeast Asia, and how it relates implicitly to India and China genetically, and what inferences we can make about demography and history. Though I will touch upon the Malay peninsula in the preliminary results, I have removed the Indonesian and Philippine samples from the data set in totality. This means that in this post I will not touch upon spread of the Austronesians.
I present before you two tentative questions:
- What was the relationship of the spread of Indic culture to Indic genes in mainland Southeast Asia before 1000 A.D.?
- What was the relationship of the spread of Tai culture to Tai genes in mainland Southeast Asia after 1000 A.D.?
The two maps above show the distribution of Austro-Asiatic and Tai languages in mainland Southeast Asia. Observe that when you join the two together in a union they cover much of the eastern 2/3 of mainland Southeast Asia. The fragmented nature of Austro-Asiatic languages in the northern region, edging into the People’s Republic of China, implies to us immediately that it is likely that in the past there was a continuous zone of Austro-Asiatic speech in this region. From the histories and mythologies of the Tai people we know that this group migrated from the southern fringes of China around ~1000 A.D. This is obvious when we note that there are still Tai people in southern China, and the expansion of the Tai across what is today Thailand is to some extent historically attested. Between 1000 and 1500 there was a wholesale ethnic reorganization of the Chao Phray river basin. Was that a matter of demographic replacement, or cultural assimilation, or some of both?
Second, what was the impact of Indians upon mainland Southeast Asia? One of the easiest ways to ascertain Indian influence is script. Burmese, Thai and Cambodian scripts all derive from Grantha, an archaic Tamil script (non-Islamic scripts in island Southeast Asia, such as Javanese and Balinese, are also derive from South Indian precursors). The Indian religious influences also are more southern than northern, manifesting in the southern forms of Shaivite Hinduism and Sri Lankan Theravada Buddhism.
The Pith: the genetic relationships between bacteria in our stomach can tell us a lot about the relationships between various groups of people. Additionally, the distribution of different strains of bacteria may have significant public health implications.
The above image is from a paper which was pushed online yesterday in PLoS ONE: Evolutionary History of Helicobacter pylori Sequences Reflect Past Human Migrations in Southeast Asia. It’s a paper which caught my attention for several reasons. First, I’ve exhibited some curiosity about the history and prehistory of Southeast Asia of late. Elucidating this region’s historical dynamics may bear upon more general questions of human evolutionary and cultural process. Second, H. pylori is a fascinating organism whose connection to specific human populations is tight enough that it can shed light on past interactions of different groups. In short, just like humans H. pylori exhibits regional specificity and local history. But additionally, H. pylori is also subject to natural selection after introduction into a new population, and so can serve as a window upon cultural contacts which might otherwise leave a light demographic footprint. In other words, the spread of H. pylori across human populations may be compared to the spread of Buddhism. This religion came to China and Japan with some Buddhists of South and Central Asian origin, but by and large its spread was memetic rather than through natural increase of a Buddhist population.
First, let’s hit the abstract:
Markers show populations sampled by HUGO Pan-Asian SNP Consortium
The Pith: Southeast Asia was settled by a series of distinct peoples. The pattern of settlement can be discerned in part by examination of patterns of genetic variation. It seems likely that Austro-Asiatic populations were dominant across the western half of Indonesia before the arrival of Austronesians.
About a year and a half ago I reviewed a paper in Science which did a first pass through some of the findings suggested by the HUGO Pan-Asian SNP Consortium data set, which pooled a wide range of Asian populations. You can see the locations on the map above (alas, the labels are too small to read the codes). The important issue in relation to this data set is that it has a thick coverage of Southeast Asia, which is not well represented in the HGDP. Unfortunately there are only ~50,000 markers, which is not optimal for really fine-grained intra-regional analysis in my opinion. But better than nothing, and definitely sufficient for coarser scale analysis.
A few things have changed since I first reviewed this paper. First, I pulled down a copy of the Pan-Asian SNP data set. I’m going to play with it myself soon. Second, after reading Strange Parallels, volume 1 and 2, I know a lot more about Southeast Asian history. Finally, the possibility of archaic admixture amongst Near Oceanians makes the genetics of the regions which were once Sundaland and Sahul of particular interest.
As I am currently reading Victor Lieberman’s magisterial Strange Parallels: Volume 2. So I was very interested in a new paper from BMC Genetics, Genetic structure of the Mon-Khmer speaking groups and their affinity to the neighbouring Tai populations in Northern Thailand, pointed to by Dienekes today. Here are the results and conclusions:
A large fraction of genetic variation is observed within populations (about 80% and 90 % for mtDNA and the Y-chromosome, respectively). The genetic divergence between populations is much higher in Mon-Khmer than in Tai speaking groups, especially at the paternally inherited markers. The two major linguistic groups are genetically distinct, but only for a marginal fraction (1 to 2 %) of the total genetic variation. Genetic distances between populations correlate with their linguistic differences, whereas the geographic distance does not explain the genetic divergence pattern.
The Mon-Khmer speaking populations in northern Thailand exhibited the genetic divergence among each other and also when compared to Tai speaking peoples. The different drift effects and the post-marital residence patterns between the two linguistic groups are the explanation for a small but significant fraction of the genetic variation pattern within and between them.
There are many occasions when it has taken a synthetic scholar to point out to me the overall structure of a constellation of facts which I was conscious of prior. So it is with Lieberman’s work. I had known that the eruption of the Thai peoples into Southeast Asia occurred with the last 1,000 years, before which the peninsula was divided between Tibeto-Burman populations to the west and Austro-Asiatic languages to the east (the latter divided between the Khmer and Vietnamese). Additionally, it is presumed that the Tibeto-Burman languages themselves displaced Austro-Asiatic in the western zone (as evident by the persistence of Mon in modern Burma). What was noted in volume 1 of Strange Parallels though is that the three geographical regions engaged with and assimilated the Thai invasions different. In the center the Thai succeeded in dominating the previous groups and imposing their identity upon the region. It is often asserted that modern Cambodia’s existence as an independent state is a function of the protection conferred upon it by the French from the expansive ambitions of the Empire of Siam. But in the east the Vietnamese state was barely impacted by the Thai folk wandering. As in China the Thai in Vietnam are marginalized “mountain tribes.” Finally, in the west, in the zone which became Burma, the Thai did not take over the cultural commanding heights. But neither were they absolutely marginalized as in the east. Rather, the Shan people became part of the of the Burmese landscape, integrated into the Theravada Buddhist culture, but also a significant secondary ethnos to the Burman majority (along with Karens, Mons, etc.).
What does this have to do with genetics? Possibly everything and nothing, and all answers in between.
The past ten years has obviously been very active in the area of human genomics, but in the domain of South Asian genetic relationships in a world wide context it has seen veritable revolutions and counter-revolutions. The final outlines are still to be determined. In the mid-1990s the conventional wisdom was that South Asians were a branch of a broader West Eurasian cluster of peoples, albeit more distant from the core Middle Eastern-North-African-European-Caucasian clade. The older physical anthropological literature would have asserted that South Asians were predominantly Caucasoid, but with a Australoid element admixed in at varying proportions as a function of geography and caste. To put it more concretely, and I think accurately, a large degree of South Asian physical variety can be defined along the spectrum between A. R. Rahman and Nawaz Sharif. The regional and caste truisms are only correlations. Subrahmanyan Chandrasekhar was a Tamil Brahmin, but experienced anti-black racism in the United States. I think that is reasonable in light of his appearance.
This rough & ready mainstream understanding, supporting by classical genetic markers, was overturned in the early years of the 21st century. One line of thought argued that South Asians were much more distinctive from the broader Western Eurasian cluster of peoples. Representative of this body of work is a paper like The genetic heritage of the earliest settlers persists both in Indian tribal and caste populations. These researchers tended to start with the female lineages, mtDNA, and then supplement that with Y lineages, the paternal descent. A separate line of evidence, generally drawn from Y chromosomal results, indicated that there were deep connections between the people of India and those of Central Eurasia, in particular via the R1a haplogroup. Additionally, one aspect of the first set of results which was very surprising was that it actually placed South Asians closer to East, not West, Eurasians. But by the end of the aughts the uniparental studies had been supplemented by a range of results produced from SNP-chips, which looked at hundreds of thousands of genetic variants. These studies seemed to support the older view of South Asians being closer to West Eurasians than East Eurasians. Finally last year a paper came out which posited that almost all South Asian populations were actually an ancient stabilized hybrid between two groups, a European-like population, “Ancient North Indians” (ANI), and another group which is no longer present in unadmixed form, “Ancient South Indians” (ASI), of whom the Andaman Islanders are distant relatives. Though there was a slight bias toward ANI as a whole, the fraction of ASI increased as one went southeast, and down the caste ladder. The distinctive “South Asian” ancestral group in other words then may actually be conceived of as a compound of these two elements; an admixture of the native substrate against a European-like genetic background.