In India, members of higher ranking castes are genetically more similar to Europeans, while lower castes are more similar to Asians, according to a study published in this month’s issue of Genome Research.
The study is from an international team led by Michael Bamshad (University of Utah) and is the most comprehensive attempt so far to explore the impact of ancient Western migrations on people in India.
The origins of people living in India are under debate. Some 5000 years ago, Indo-European speaking people from West Eurasia entered India and purportedly mixed with native proto-Asian populations in the region. Historians believe these West Eurasian immigrants established the present Hindu caste system, while appointing themselves to higher rank castes.
In this scenario, members of higher rank castes should exhibit a closer genetic relationship to Europeans than lower rank castes, given the taboos prohibiting intercaste marriages. However, previous genetic studies with a limited focus have not produced a consensus on Indian origins. The present study compares maternally inherited DNA variations, paternally inherited variations, and bi-parentally inherited variations between 265 Indian males of different castes and 750 African, European, Asian, and other Indian males. The detailed comparison revealed that genetic similarities between Indians and Europeans tend to increase with caste rank.
Intriguingly, the scientists found different trends when comparing maternally inherited (mitochondrial) variations and paternally inherited (Y chromosome) variations. Maternally inherited DNA in Indian populations was overall more similar to Asians than to Europeans, though similarity to Europeans increased with rank. Paternally inherited DNA, on the other hand, was overall more similar to Europeans than to Asians. These results support the notion that the West Eurasian immigrants mixing with native populations were mostly male, and that they tended to insert themselves into high ranking positions in the developing Hindu Indian caste system.
Materials provided by Cold Spring Harbor Laboratory. Note: Content may be edited for style and length.
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