12-02-2004, 06:46 AM
http://www.gnxp.com/MT2/archives/002641.html
August 29, 2004
Genetics of caste in India
The two biggest & best studies of the genetics of caste in India are Majumder 2003 and Bamshad 2001 (both links to PDFs, see also Majumder commentary on Bamshad 2001). Here are two layman's summaries, and then my comments:
Majumder:
The Dravidian tribals were widespread throughout India before the arrival of the Indo-European (IE) nomads. This conclusion is consistent with historical and linguistic inferences (Thapar, Renfrew). The latter suggest that when the ranked caste system was formed after the arrival of the IE speakers about 3500 ybp, many indigenous DR people embraced (freely or forced) the caste system. As the IE speakers advanced into the Gangetic plain, many of the DR tribes retreated to the Southern parts of India to avoid dominance.
The Central Asian populations have contributed to the genetic profiles of upper castes, more so in the North of India than in the South. They are also genetically closer to the upper-caste than to the middle or lower-caste populations.
This finding is in agreement with an earlier DNA analysis by some Andhra University scientists (B.B. Rao, M. Naidu, B.V.R Prasad, and others). It also suggests, in keeping with the point above, that even after the DR speakers retreated to the South to avoid elite dominance, there has been admixture between Central and West Asians and Northern Indian populations in peninsular India.
As a final point, the Majumder group concludes that all this historical gene flow has pretty much obliterated genetic histories of the contemporary populations of India today. As a result, there is now no clear congruence of genetic and geographical or sociocultural affinities.
Layman's summary of Majumder 2003:
An international study led by Michael J. Bamshad of the Eccles Institute of Human Genetics of the University of Utah of caste origins has found (the findings have been reported in a recent issue of the journal Genome Research) that members of the upper castes are genetically more similar to Europeans, Western Eurasians to be specific, whereas the lower castes are more similar to Asians. This finding is in tune with the expectations based on historical reasoning and the prevalent views of many social historians. In exercising their superiority over native proto-Asian populations, the Aryans would have appointed themselves to higher rank castes. The 18-member research team includes scientists from the United States, the United Kingdom, India and Estonia. The collaborating Indian scientists were anthropologists Bhaskar Rao, J. Mastan Naidu and B. V. Ravi Prasad from Andhra University, Visakhapatnam, and P. Govinda Reddy from the University of Madras.
There have been genetic studies in the past that tried to answer this question but their results have been equivocal, in the sense that some have found European origins and some Asian origins. According to Partha P. Majumder, a population geneticist with the Indian Statistical Institute (ISI), Kolkata, who has written a commentary on the work in the same issue of the journal, the primary reason for this was the lack of data on a large uniform set of genetic markers from populations of India and central/west Asia. This study, where the researchers have used a battery of genomic markers and DNA sequences spanning three genomic regions, is a landmark, says Majumder. "The study provides an incisive genomic view of castes and their origins," he has written.
Upshot:
1. Both studies confirm that caste is a strong predictor of genome content.
2. The "Asian" referred to in both studies is a proto-Asian Dravidian native to the subcontinent, not a modern East Asian.
3. The similarities between upper castes and Eastern Europeans should not be overplayed; it really depends what locus you look at. Some loci (especially on the Y) appear to be very similar to Eastern European populations among upper castes, while some autosomal loci do not.
4. One of the most interesting findings is that the combination of caste stratification and geographic mixing has made it difficult to predict genome content from one's location in the subcontinent.
More studies are on the way, but these are the best two as they employ several autosomal loci rather than focusing entirely on Y-chromosomal data. It is being found that frequently the male and female ancestors of a population have different evolutionary histories, which is why Y-chromosomal analyses alone are insufficient. This occurs when invading or settling males have settled down with local women.
Posted by godless at 04:25 PM
August 29, 2004
Genetics of caste in India
The two biggest & best studies of the genetics of caste in India are Majumder 2003 and Bamshad 2001 (both links to PDFs, see also Majumder commentary on Bamshad 2001). Here are two layman's summaries, and then my comments:
Majumder:
The Dravidian tribals were widespread throughout India before the arrival of the Indo-European (IE) nomads. This conclusion is consistent with historical and linguistic inferences (Thapar, Renfrew). The latter suggest that when the ranked caste system was formed after the arrival of the IE speakers about 3500 ybp, many indigenous DR people embraced (freely or forced) the caste system. As the IE speakers advanced into the Gangetic plain, many of the DR tribes retreated to the Southern parts of India to avoid dominance.
The Central Asian populations have contributed to the genetic profiles of upper castes, more so in the North of India than in the South. They are also genetically closer to the upper-caste than to the middle or lower-caste populations.
This finding is in agreement with an earlier DNA analysis by some Andhra University scientists (B.B. Rao, M. Naidu, B.V.R Prasad, and others). It also suggests, in keeping with the point above, that even after the DR speakers retreated to the South to avoid elite dominance, there has been admixture between Central and West Asians and Northern Indian populations in peninsular India.
As a final point, the Majumder group concludes that all this historical gene flow has pretty much obliterated genetic histories of the contemporary populations of India today. As a result, there is now no clear congruence of genetic and geographical or sociocultural affinities.
Layman's summary of Majumder 2003:
An international study led by Michael J. Bamshad of the Eccles Institute of Human Genetics of the University of Utah of caste origins has found (the findings have been reported in a recent issue of the journal Genome Research) that members of the upper castes are genetically more similar to Europeans, Western Eurasians to be specific, whereas the lower castes are more similar to Asians. This finding is in tune with the expectations based on historical reasoning and the prevalent views of many social historians. In exercising their superiority over native proto-Asian populations, the Aryans would have appointed themselves to higher rank castes. The 18-member research team includes scientists from the United States, the United Kingdom, India and Estonia. The collaborating Indian scientists were anthropologists Bhaskar Rao, J. Mastan Naidu and B. V. Ravi Prasad from Andhra University, Visakhapatnam, and P. Govinda Reddy from the University of Madras.
There have been genetic studies in the past that tried to answer this question but their results have been equivocal, in the sense that some have found European origins and some Asian origins. According to Partha P. Majumder, a population geneticist with the Indian Statistical Institute (ISI), Kolkata, who has written a commentary on the work in the same issue of the journal, the primary reason for this was the lack of data on a large uniform set of genetic markers from populations of India and central/west Asia. This study, where the researchers have used a battery of genomic markers and DNA sequences spanning three genomic regions, is a landmark, says Majumder. "The study provides an incisive genomic view of castes and their origins," he has written.
Upshot:
1. Both studies confirm that caste is a strong predictor of genome content.
2. The "Asian" referred to in both studies is a proto-Asian Dravidian native to the subcontinent, not a modern East Asian.
3. The similarities between upper castes and Eastern Europeans should not be overplayed; it really depends what locus you look at. Some loci (especially on the Y) appear to be very similar to Eastern European populations among upper castes, while some autosomal loci do not.
4. One of the most interesting findings is that the combination of caste stratification and geographic mixing has made it difficult to predict genome content from one's location in the subcontinent.
More studies are on the way, but these are the best two as they employ several autosomal loci rather than focusing entirely on Y-chromosomal data. It is being found that frequently the male and female ancestors of a population have different evolutionary histories, which is why Y-chromosomal analyses alone are insufficient. This occurs when invading or settling males have settled down with local women.
Posted by godless at 04:25 PM