INDIA’S caste system has left indelible marks on the genes of modern Hindus, according to a group of Indian and American researchers. The team told a meeting of the American Association of Physical Anthropology that they collected blood samples from 300 unrelated Indian men of all ranks in the hierarchy. Then they compared genes from the Y chromosome, which traces paternal ancestry, and from mitochondria, which is inherited only through the material line.

The results reveal that the rules of caste were far more rigidly enforced for men than for women. While it was always possible for a woman to advance by marrying a man in a higher caste, this was not possible for men. As a result, the mitochondrial DNA shows slight blurring of the caste lines, while the Y chromosome DNA segregates clearly into different castes.

The team also found that higher castes resemble Caucasians more than they do Asians. This fits the historical belief that the caste system was imposed by Caucasians who swept into India from the northwest.