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Genetic evidence suggests European migrants may have influenced
the origins of India's caste system
  
By Bijal P. Trivedi

A new study has revealed that Indians belonging to higher castes are genetically closer to Europeans than are individuals from lower castes, whose genetic profiles are closer to those of Asians.



The study compared genetic markers—located on the Y chromosome and the mitochondrial DNA—between 265 Indian men of various castes and 750 African, Asian, European and other Indian men. To broaden the study, 40 markers from chromosomes 1 to 22 were analyzed from more than 600 individuals from different castes and continents. The comparison of the markers among these groups confirmed that genetic similarities to Europeans increased as caste rank increased.

The study, led by Michael Bamshad of the University of Utah, in Salt Lake City, and his colleagues, is reported to be the most comprehensive genetic analysis to date of the impact of European migrations on the structure and origin of the current Indian population. The article appears in the current issue of Genome Research.

The caste system, defined in ancient Sanskrit texts, determines a person's rank in society: The Brahmin, who were traditionally priests and scholars, held the highest rank in Hindu society. Warriors and rulers made up the Kshatriya who were the next in line to the Brahmin. Merchants, traders, farmers, and artisans were the third caste called the Vysya. The Shudra were the fourth rank and consisted of laborers. Because of strict rules forbidding marriage between men and women of different castes, these four classes remained distinct for thousands of years.

Bamshad's team found that Y chromosomes from the Brahmin and Kshatriya closely resembled European Y chromosomes rather than Asian Y chromosomes. The Y chromosomes from the lower castes bore more similarities to the Asian Y chromosome. The mitochondrial DNA showed the same pattern.

The authors believe their results support the notion that Europeans who migrated into India between 3,000 and 8,000 years ago may have merged with or imposed their social structure on the native northern Indians and placed themselves into the highest castes.

Analysis of the paternally transmitted Y chromosome among Indians in general indicated that the Y chromosome had a more European flavor. Maternally inherited mitochondrial DNA among Indians is more Asian than European. This suggests that the Europeans who entered India were predominantly male.

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Bamshad, M. et al. Genetic evidence on the origins of Indian caste populations. Genome Res 11, 994-1004 (May 2001).
 
Majumder, P.P. Indian caste origins: genomic insights and future outlook. Genome Res 11, 931-932 (May 2001).
 

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