Indian population is 'genetic hotchpotch' of two different ancestral groups

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London, September 24 (ANI): The largest DNA survey of Indian heritage to date has revealed that the current population of India is a genetic hotchpotch of two distinct ancestral groups.

India makes up around one-sixth of the world's population, yet the South Asian country has been sorely under-represented in genome-wide studies of human genetic variation.

Now, according to a report by Nature News, a team led by David Reich of the Broad Institute in Cambridge, Massachusetts, and Lalji Singh of the Centre for Cellular and Molecular Biology in Hyderabad, India, has probed more than 560,000 SNPs (single nucleotide polymorphisms) across the genomes of 132 Indian individuals from 25 diverse ethnic and tribal groups dotted all over India.

"There are populations that have lived in the same town and same village for thousands of years without exchanging genes," said Reich.

The researchers showed that most Indian populations are genetic admixtures of two ancient, genetically divergent groups, which each contributed around 40-60 percent of the DNA to most present-day populations.

One ancestral lineage - which is genetically similar to Middle Eastern, Central Asian and European populations - was higher in upper-caste individuals and speakers of Indo-European languages such as Hindi, the researchers found.

The other lineage was not close to any group outside the subcontinent, and was most common in people indigenous to the Andaman Islands, a remote archipelago in the Bay of Bengal.

The researchers also found that Indian populations were much more highly subdivided than European populations.

But whereas European ancestry is mostly carved up by geography, Indian segregation was driven largely by caste.

"There are populations that have lived in the same town and same village for thousands of years without exchanging genes," said Reich.

The study suggested that Indian populations, although currently huge in number, were also founded by relatively small bands of individuals.

According to Reich, overall, the picture that emerges is of ancient genetic mixture, followed by fragmentation into small, isolated ethnic groups, which were then kept distinct for thousands of years because of limited intermarriage - a practice also known as endogamy.

The small numbers of founders of each Indian group also have clinical consequences, according to Reich.

"There will be a lot of recessive diseases in India that will be different in each population and that can be searched for and mapped genetically," he said. "That will be important for health in India," he added. (ANI)

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