August 14, 2005

Population genetics of Indus Valley populations

A new article confirms that the genetic composition of the population of the Indo-Gangetic plain (Pakistan and NW India) consists of West Eurasian (Caucasoid) and indigenous South Asian elements. The contribution of other elements such as Sub-Saharan African in the Makrani "Negroids", the significant contribution of indigenous female South Asian elements to the Parsis (who are of Iranian origin, but live in India), and the contribution of Mongoloid elements in groups such as the Hunza, and the Hazara is also confirmed. The mtDNA distribution is shown below:

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In terms of their Y-chromosome, the population of the region is of western Eurasian (Caucasoid) origin, also including a variant which has developed in the region and is found at lesser frequency elsewhere:
In striking contrast to the mtDNA data, there is no strong evidence in Pakistani populations of Y-chromosome signatures of the early inhabitants of the region following the African exodus (Qamar et al. 2002, Zerjal et al. 2002), with their Y-chromosomes largely replaced by subsequent migrations or gene flow. The Y-chromosome gene pool of Pakistani populations is mainly attributable to western Eurasian lineages, particularly from the Middle East (Qamar et al. 2002). Conversely, few traces of East Asian haplogroups are observed in the Indus Valley populations. One Y-chromosome haplogroup (L-M20) has a high mean frequency of 14% in Pakistan and so differs from all other haplogroups in its frequency distribution. L-M20 is also observed, although at lower frequencies, in neighbouring countries, such as India, Tajikistan, Uzbekistan and Russia. Both the frequency distribution and estimated expansion time (~7,000 YBP) of this lineage suggest that its spread in the Indus Valley may be associated with the expansion of local farming groups during the Neolithic period (Qamar et al. 2002).


For easier access, here is a break-down of Indian Y-chromosomal distribution taken from a recent comprehensive study (pdf).

And, a similar study on Y-chromosomal distribution from Pakistan (pdf):

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Annals of Human Biology Mar-Apr 32(2):154-62.

A population genetics perspective of the Indus Valley through uniparentally-inherited markers.

McElreavey K and Quintana-Murci L.

Analysis of mtDNA and Y-chromosome variation in the Indo-Gangetic plains shows that it was a region where genetic components of different geographical origins (from west, east and south) met. The genetic architecture of the populations now living in the area comprise genetic components dating back to different time-periods during the Palaeolithic and the Neolithic. mtDNA data analysis has demonstrated a number of deep-rooting lineages of Pleistocene origin that may be witness to the arrival of the first settlers of South and Southwest Asia after humans left Africa around 60,000 YBP. In addition, comparisons of Y-chromosome and mtDNA data have indicated a number of recent and sexually asymmetrical demographic events, such as the migrations of the Parsis from Iran to India, and the maternal traces of the East African slave trade.


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