XPost: alt.religion.hindu, soc.history, soc.culture.indian   
   XPost: alt.religion, alt.politics.religion   
   From: hayesstw@telkomsa.net   
      
    How genetics is settling the Aryan migration debate   
   Tony Joseph   
   June 16, 2017 23:49 IST   
   Updated: June 17, 2017 13:16 IST   
      
   New DNA evidence is solving the most fought-over question in Indian   
   history. And you will be surprised at how sure-footed the answer is,   
   writes Tony Joseph   
      
   The thorniest, most fought-over question in Indian history is slowly   
   but surely getting answered: did Indo-European language speakers, who   
   called themselves Aryans, stream into India sometime around 2,000 BC –   
   1,500 BC when the Indus Valley civilisation came to an end, bringing   
   with them Sanskrit and a distinctive set of cultural practices?   
   Genetic research based on an avalanche of new DNA evidence is making   
   scientists around the world converge on an unambiguous answer: yes,   
   they did.   
      
   This may come as a surprise to many — and a shock to some — because   
   the dominant narrative in recent years has been that genetics research   
   had thoroughly disproved the Aryan migration theory. This   
   interpretation was always a bit of a stretch as anyone who read the   
   nuanced scientific papers in the original knew. But now it has broken   
   apart altogether under a flood of new data on Y-chromosomes (or   
   chromosomes that are transmitted through the male parental line, from   
   father to son).   
      
   Lines of descent   
      
   Until recently, only data on mtDNA (or matrilineal DNA, transmitted   
   only from mother to daughter) were available and that seemed to   
   suggest there was little external infusion into the Indian gene pool   
   over the last 12,500 years or so. New Y-DNA data has turned that   
   conclusion upside down, with strong evidence of external infusion of   
   genes into the Indian male lineage during the period in question.   
      
   The reason for the difference in mtDNA and Y-DNA data is obvious in   
   hindsight: there was strong sex bias in Bronze Age migrations. In   
   other words, those who migrated were predominantly male and,   
   therefore, those gene flows do not really show up in the mtDNA data.   
   On the other hand, they do show up in the Y-DNA data: specifically,   
   about 17.5% of Indian male lineage has been found to belong to   
   haplogroup R1a (haplogroups identify a single line of descent), which   
   is today spread across Central Asia, Europe and South Asia.   
   Pontic-Caspian Steppe is seen as the region from where R1a spread both   
   west and east, splitting into different sub-branches along the way.   
      
   The paper that put all of the recent discoveries together into a tight   
   and coherent history of migrations into India was published just three   
   months ago in a peer-reviewed journal called ‘BMC Evolutionary   
   Biology’. In that paper, titled “A Genetic Chronology for the Indian   
   Subcontinent Points to Heavily Sex-biased Dispersals”, 16 scientists   
   led by Prof. Martin P. Richards of the University of Huddersfield,   
   U.K., concluded: “Genetic influx from Central Asia in the Bronze Age   
   was strongly male-driven, consistent with the patriarchal, patrilocal   
   and patrilineal social structure attributed to the inferred   
   pastoralist early Indo-European society. This was part of a much wider   
   process of Indo-European expansion, with an ultimate source in the   
   Pontic-Caspian region, which carried closely related Y-chromosome   
   lineages… across a vast swathe of Eurasia between 5,000 and 3,500   
   years ago”.   
      
   In an email exchange, Prof. Richards said the prevalence of R1a in   
   India was “very powerful evidence for a substantial Bronze Age   
   migration from central Asia that most likely brought Indo-European   
   speakers to India.” The robust conclusions of Professor Richards and   
   his team rest on their own substantive research as well as a vast   
   trove of new data and findings that have become available in recent   
   years, through the work of genetic scientists around the world.   
      
   What’s happened very rapidly, dramatically, and powerfully in the last   
   few years has been the explosion of genome-wide studies of human   
   history based on modern and ancient DNA, and that’s been enabled by   
   the technology of genomics and the technology of ancient DNA....”   
   David Reich, Geneticist and professor, Harvard Medical School   
      
   Peter Underhill, scientist at the Department of Genetics at the   
   Stanford University School of Medicine, is one of those at the centre   
   of the action. Three years ago, a team of 32 scientists he led   
   published a massive study mapping the distribution and linkages of   
   R1a. It used a panel of 16,244 male subjects from 126 populations   
   across Eurasia. Dr. Underhill’s research found that R1a had two   
   sub-haplogroups, one found primarily in Europe and the other confined   
   to Central and South Asia. Ninety-six per cent of the R1a samples in   
   Europe belonged to sub-haplogroup Z282, while 98.4% of the Central and   
   South Asian R1a lineages belonged to sub-haplogroup Z93. The two   
   groups diverged from each other only about 5,800 years ago. Dr.   
   Underhill’s research showed that within the Z93 that is predominant in   
   India, there is a further splintering into multiple branches. The   
   paper found this “star-like branching” indicative of rapid growth and   
   dispersal. So if you want to know the approximate period when   
   Indo-European language speakers came and rapidly spread across India,   
   you need to discover the date when Z93 splintered into its own various   
   subgroups or lineages. We will come back to this later.   
      
   So in a nutshell: R1a is distributed all over Europe, Central Asia and   
   South Asia; its sub-group Z282 is distributed only in Europe while   
   another subgroup Z93 is distributed only in parts of Central Asia and   
   South Asia; and three major subgroups of Z93 are distributed only in   
   India, Pakistan, Afghanistan and the Himalayas. This clear picture of   
   the distribution of R1a has finally put paid to an earlier hypothesis   
   that this haplogroup perhaps originated in India and then spread   
   outwards. This hypothesis was based on the erroneous assumption that   
   R1a lineages in India had huge diversity compared to other regions,   
   which could be indicative of its origin here. As Prof. Richards puts   
   it, “the idea that R1a is very diverse in India, which was largely   
   based on fuzzy microsatellite data, has been laid to rest” thanks to   
   the arrival of large numbers of genomic Y-chromosome data.   
      
   Gene-dating the migration   
      
   Now that we know that there WAS indeed a significant inflow of genes   
   from Central Asia into India in the Bronze Age, can we get a better   
   fix on the timing, especially the splintering of Z93 into its own   
   sub-lineages? Yes, we can; the research paper that answers this   
      
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