for National Geographic News
Most modern Indians descended from South Asians, not invading Central Asian steppe dwellers, a new genetic study reports.
The Indian subcontinent may have acquired agricultural techniques and languagesbut it absorbed few genesfrom the west, said Vijendra Kashyap, director of India's National Institute of Biologicals in Noida.
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The finding disputes a long-held theory that a large invasion of central Asians, traveling through a northwest Indian corridor, shaped the language, culture, and gene pool of many modern Indians within the past 10,000 years.
That theory is bolstered by the presence of Indo-European languages in India, the archaeological record, and historic sources such as the Rig Veda, an early Indian religious text.
Some previous genetic studies have also supported the concept.
But Kashyap's findings, published in the current issue of the Proceedings of the National Academies of Science, stand at odds with those results.
Testing a sample of men from 32 tribal and 45 caste groups throughout India, Kashyap's team examined 936 Y chromosomes. (The chromosome determines gender; males carry it, but women do not.)
The data reveal that the large majority of modern Indians descended from South Asian ancestors who lived on the Indian subcontinent before an influx of agricultural techniques from the north and west arrived some 10,000 years ago.
Most geneticists believe that humans first reached India via a coastal migration route perhaps 50,000 years ago.
Soon after leaving Africa, these early humans are believed to have followed the coast through southern India and eventually continued on to populate distant Australia.
Peter Underhill, a research scientist at the Stanford University School of Medicine's department of genetics, says he harbors no doubts that Indo-European speakers did move into India. But he agrees with Kashyap that their genetic contribution appears small.
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