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Archived Comments for: Genetic affinities among the lower castes and tribal groups of India: inference from Y chromosome and mitochondrial DNA

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  1. O2a-M95 Clade

    Balaji Athreyan, Private Individual

    25 August 2006

    (1) There are a couple of minor typographical errors. The authors refer to the "J172 clad" instead of "J172 clade". In another place they write "sister clads" instead of "sister clades".

    (2) The authors assume that the O2a-M95 clade dates to the initial settlement of the Indian subcontinent by moderen humans some 60,000 years ago and that this clade spread to Southeast Asia from India. This is highly unlikely.

    The two excellent papers on Indian Y-chromosomes earlier this year, Sahoo et al., Proc. Nat. Acad. Sci., vol. 103, no. 4, 843-848, Jan. 2006 and Sengupta et al., Am. J. Hum. Gen., vol. 78, 202-221, Feb. 2006 both suggest an exogenous origin for M95.

    It is most likely that migrants from Southeast Asia speaking Austro-Asiatic langauges introduced this clade to India via the Northeast border region.

    (3) The conclusions of this paper are based essentially on the data presented in Table 5 - analysis of molecular variance.

    This table shows that the percentage of variance among tribal groups in mtDNA is 6.38%. Yet the authors state that the vast majority of the Indian maternal gene pool is genetically more or less uniform. This is a reasonable conclusion since the tribes are small endogamous groups subject to the effects of drift.

    But by the same token, most castes are also small endogamous groups. The authors are making a lot from the 6.17% variance between tribes and upper castes in Y-chromosome DNA when this number is actually smaller than the 6.38% variance in mtDNA between the tribes themselves!

    Table 4 of the paper shows that all the major Y-chromosome haplogroups found in India are present in all caste and tribal groups. The major difference is in the O clades which are more than 4 times as prevalent among the tribes as among the upper castes.

    I do not believe the conclusions of the paper are warranted by the data presented. The most that can be said with the data at hand is in the words of Kivisild et al. "The genetic heritage of the earliest settlers persists both in Indian tribal and caste populations".

    Competing interests


  2. Origin of Indian caste system!

    T Srinath, Madras University

    1 September 2006

    The article has a shallow depth of analysis, only based on AMOVA (analysis of molecular variance) authors’ tried to make a bulletproof conclusion on structuring of Indian populations.

    1. The extensive study of India by Metspalu et al. 2004 observed a very low frequency of Western Eurasian haplogroups in India both castes as well as in tribes while, authors’ found a comparatively higher frequency in Upper castes without any literature survey.

    2. The 85% presence of Y chromosomal haplogroup H in hierarchal Hindu Caste system is a serious observation which needs to be clarified.

    3. In figure legend 1. 16517 should be 16519. In supplementary 2. The W36 haplotype should be from K haplogroup and this should also change in Fig.1. The presence of 15670 (M2 marker) in several haplogroup background is very unlikely.

    Overall this paper doesn’t make any sense in the field of Indian complex caste system.

    Competing interests