Tuesday, June 7, 2011

Summary genetic origins of Indians

Nice detailed article here.

Summary points:

  • "Who were the ANI (Ancestral north indians)? I think they derive from a set of farming populations from between the Black Sea and the Caspian. The reason I think this is that there are suggestive associations with populations around the Caucasus with Indian groups, even more than with Iranians! This sort of “geographic leapfrog” requires a macrohistorical explanation.
  • Were the ANI Aryans? I don’t think so. The admixture event with ASI (Ancestral south indians) is very old. Likely within the last 10,000 years, but probably older than 4,000 years (I know this from personal communication with one of the researchers who attempted linkage disequilibrium decay based time-from-admixture tests). Some of the Caucasian groups which have an affinity with Indians are not Indo-European speaking.
  • So why did ANI arrive in India? I think it has to do with farming. Recent evidence is now pointing to massive reconfigurations of genetic variation across the world in the past 10,000 years. We have semi-historical evidence for nearly total replacement in Japan and Africa. But there is now a great deal of circumstantial evidence that the same occurred in Europe, at least once, and probably more than once. The ANI were one of the great farming Diasporas to pulse out of the Near East.
  • But why didn’t they replace ASI? I am not an archaeologist, so I am on weak ground here insofar as I’m relying heavily on others who know this stuff. But I suspect that the indigenous populations of the Indian subcontinent themselves had started an independent transition to farming. The ANI-ASI synthesis, both genetic and cultural, was that of two incipient farming toolkits. In contrast the relatives of the ASI in Southeast Asia did not enter into an independent phase of farming, and were marginalized to a far greater extent by populations from southern China (the exceptions being the Papuans). The Andaman Islanders then are exceptions, and not representative in their hunter-gatherer lifestyle.
  • What about the Aryans? The data from Europe is far thicker than from the Indian subcontinent, and there there is evidence for multiple movements and cultural influences. I believe that the Indo-Aryans arrived later, and are a minor overlay upon the ANI-ASI synthesis (South Indian tribals have 30-40% ANI, indicating how old and thoroughgoing the synthesis was). Some speculative suggestions can be made from the genetic data in regards to a post-ANI West Eurasian influence which does not seem Middle Eastern. I will leave that for now because we just don’t have much to go on, though I do suggest that one keep track of The Jatt Gene. I think the answers we’ve long been waiting for will be coming soon, especially with the imminent release of Indian populations from the 1000 Genomes.
  • The northwest-southeast axis is the dominant genetic story of India, but not the only one. There is a northeast-southwest axis. It seems probable that the Munda are relative newcomers as well. Though mostly Indian, there is an element of ancestry in these populations which suggests relatively recent affinities with East Asians. This is probably at least part of my personal story, so I take an interest in this “third wheel” component of our heritage.
  • South Indian Brahmins claim northern Indo-Aryan origins. The genetics certainly bear this out, albeit with some probable admixture with the local substrate. There are many specific questions which can be asked and answered. The Cochin and Bene Israel Jews of the west coast of India clearly do have highly elevated Middle Eastern components of ancestry, though they are highly admixed with the native populations. My own question: do the Nasrani Christians truly descend from Jews? I would have dismissed this outright a few months ago, but I am not sure sure now. The western coast of India seems to have long-standing connections to southern Arabia, so we need to flesh out these patterns in more detail."

Key Take away:
We all know that there is a big difference between a Kashmiri Pandit and an Adivasi from South India. But about one third of the Pandit’s ancestry is “Ancestral South Indian,” which is almost absent outside of the subcontinent. And about one third of the Adivasi’s ancestry is “Ancestral North Indian,” which connects this individual with the populations which span the Atlantic, to the Urals, to the Sahara

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