DNA trawl shows long history of India's castes
By Maggie Fox, Health and Science Editor
WASHINGTON (Reuters) - A genetic search of India's diverse populations shows most people have mixtures of European and ancient south Indian genes, and helps illustrate the deep roots of the country's caste system, researchers reported on Wednesday.
It also shows that Indians, much like the Finns and European-origin Jews, may be susceptible to recessive genetic diseases, they report in the journal Nature.
Dr. David Reich of Harvard Medical School in Boston and colleagues found "strong evidence for two ancient populations, genetically divergent, that are ancestral to most Indians today".
"One, the 'Ancestral North Indians', is genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the 'Ancestral South Indians', is as distinct from ancestral north Indians and East Asians as they are from each other," they wrote.
"Nobody's even close to having all of one or the other," Reich said in a telephone interview. "People in India are almost all a mixture of these two ancestral populations."
And virtually all also carry a risk of genetic mutations that can confer disease, Reich said.
He said his group and others should look in to that, to see if Indians have higher rates of recessive diseases, which can include deadly and incurable cystic fibrosis, sickle cell disease, and Tay-Sachs disease.
Reich's team, including a group at the Broad Institute at Harvard and the Massachusetts Institute of Technology, looked at genetic mutations in people from 25 different Indian groups -- a small sampling of the 6,000 or so estimated groups that restrict intermarriage. Continued...