01-22-2006, 03:01 AM
A prehistory of Indian Y chromosomes: Evaluating demic diffusion scenarios
Sanghamitra Sahoo, Anamika Singh, G. Himabindu, Jheelam Banerjee, T. Sitalaximi, Sonali Gaikwad, R. Trivedi, Phillip Endicott, Toomas Kivisild, Mait Metspalu, Richard Villems, and V. K. Kashyap
from the ABSTRACT
"The sharing of some Y-chromosomal haplogroups between Indian and Central Asian populations is most parsimoniously explained by a deep, common ancestry between the two regions, with <b>diffusion of some Indian-specific lineages northward. </b> The Y-chromosomal data consistently suggest a largely South Asian origin for Indian caste communities and therefore argue against any major influx, from regions north and west of India, of people associated either with the development of agriculture or the spread of the Indo-Aryan language family."
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Several studies have argued that, in contrast to the relative uniformity of mtDNA, the Y chromosomes of Indian populations display relatively small genetic distances to those of West Eurasians (17), linking this finding to hypothetical migrations by Indo-Aryan speakers. Wells et al. (18) highlighted M17 (R1a) as a potential marker for one such event, as it demonstrates decreasing frequencies from Central Asia toward South India.
Departing from the Ëone haplogroup equals one migration " scenario, Cordaux et al. (19) defined, heuristically, a package of haplogroups (J2, R1a, R2, and L) to be associated with the migration of IE people and the introduction of the caste system to India, again from Central Asia, because they had been observed at significantly lower proportions in South Indian tribal groups, with the high frequency of R1a among Chenchus of Andhra Pradesh (6) considered as an aberrant phenomenon (19). Conversely, haplogroups H, F*, and O2a, which were observed at significantly higher proportions among tribal groups of South India, led the same authors to single them out as having an indigenous Indian origin. Only O3e was envisaged as originating (recently) east of India (20), substantiating a linguistic correlation with the TB speakers of Southeast Asia...."
"In other words, if the source of R1a variation in India comes from Central Asia, as claimed by Wells et al. (18) and Cordaux et al. (19), then, under a recent gene flow scenario, one would expect to find the other Central Asian-derived NRY haplogroups (C3, DE, J*, I, G, N, O) in Northwest India at similarly elevated frequencies, but that is not the case. Alternatively, although the simple admixture scenario does not hold, one could nevertheless argue that the other haplogroups were lost during a hypothetical bottleneck (lineage sorting among the early Indo-Aryans arriving to India). But in line with this scenario, one should expect to observe dramatically lower genetic variation among Indian R1a lineages. In fact, the opposite is true"
"Indo-Aryan migration scenario advocated in ref. 19 rested on the suggestion that all Indian caste groups are similar to each other while being significantly different from the tribes. Using a much more representative data set, numerically, geographically, and definitively, it was not possible to confirm any of the purported differentiations between the caste and tribal pools. Although differences could be found to occur within particular regions, between particular caste and tribal groups, consistent and statistically significant variations at the subcontinental scale were not detected."
"It is not necessary, based on the current evidence, to look beyond South Asia for the origins of the paternal heritage of the majority of Indians at the time of the onset of settled agriculture. The perennial concept of people, language, and agriculture arriving to India together through the northwest corridor does not hold up to close scrutiny"
Sanghamitra Sahoo, Anamika Singh, G. Himabindu, Jheelam Banerjee, T. Sitalaximi, Sonali Gaikwad, R. Trivedi, Phillip Endicott, Toomas Kivisild, Mait Metspalu, Richard Villems, and V. K. Kashyap
from the ABSTRACT
"The sharing of some Y-chromosomal haplogroups between Indian and Central Asian populations is most parsimoniously explained by a deep, common ancestry between the two regions, with <b>diffusion of some Indian-specific lineages northward. </b> The Y-chromosomal data consistently suggest a largely South Asian origin for Indian caste communities and therefore argue against any major influx, from regions north and west of India, of people associated either with the development of agriculture or the spread of the Indo-Aryan language family."
---------------------------------------------------------------
Several studies have argued that, in contrast to the relative uniformity of mtDNA, the Y chromosomes of Indian populations display relatively small genetic distances to those of West Eurasians (17), linking this finding to hypothetical migrations by Indo-Aryan speakers. Wells et al. (18) highlighted M17 (R1a) as a potential marker for one such event, as it demonstrates decreasing frequencies from Central Asia toward South India.
Departing from the Ëone haplogroup equals one migration " scenario, Cordaux et al. (19) defined, heuristically, a package of haplogroups (J2, R1a, R2, and L) to be associated with the migration of IE people and the introduction of the caste system to India, again from Central Asia, because they had been observed at significantly lower proportions in South Indian tribal groups, with the high frequency of R1a among Chenchus of Andhra Pradesh (6) considered as an aberrant phenomenon (19). Conversely, haplogroups H, F*, and O2a, which were observed at significantly higher proportions among tribal groups of South India, led the same authors to single them out as having an indigenous Indian origin. Only O3e was envisaged as originating (recently) east of India (20), substantiating a linguistic correlation with the TB speakers of Southeast Asia...."
"In other words, if the source of R1a variation in India comes from Central Asia, as claimed by Wells et al. (18) and Cordaux et al. (19), then, under a recent gene flow scenario, one would expect to find the other Central Asian-derived NRY haplogroups (C3, DE, J*, I, G, N, O) in Northwest India at similarly elevated frequencies, but that is not the case. Alternatively, although the simple admixture scenario does not hold, one could nevertheless argue that the other haplogroups were lost during a hypothetical bottleneck (lineage sorting among the early Indo-Aryans arriving to India). But in line with this scenario, one should expect to observe dramatically lower genetic variation among Indian R1a lineages. In fact, the opposite is true"
"Indo-Aryan migration scenario advocated in ref. 19 rested on the suggestion that all Indian caste groups are similar to each other while being significantly different from the tribes. Using a much more representative data set, numerically, geographically, and definitively, it was not possible to confirm any of the purported differentiations between the caste and tribal pools. Although differences could be found to occur within particular regions, between particular caste and tribal groups, consistent and statistically significant variations at the subcontinental scale were not detected."
"It is not necessary, based on the current evidence, to look beyond South Asia for the origins of the paternal heritage of the majority of Indians at the time of the onset of settled agriculture. The perennial concept of people, language, and agriculture arriving to India together through the northwest corridor does not hold up to close scrutiny"