Study finds sixth genetic ancestry of Indians in genes of Koraga tribes living in Dakshina Kannada, Udupi

New Delhi: Genetic signatures found in a marginalised tribe in coastal Karnataka and Kerala have provided an Indo-European team of scientists with a breakthrough to untangle the complex migratory history of modern Indians, whose ancestors reached the subcontinent thousands of years ago from diverse regions across the globe.

While five genetic components of Indian ancestry are known, the team has now spotted a previously unidentified sixth one relying on the clues hidden in the genes of Koraga tribes living in Dakshina Kannada and Udupi districts of Karnataka and Kasaragod district of Kerala.

“We call these distinct signatures as “proto-Dravidian”, which emerged around the dawn of the Indus Valley Civilisation around 4,400 years ago,” team leader Ranajit Das, a geneticist at Yenepoya University, Mangalore told DH.

Others in the team - Jaison Jeevan Sequeira, Mohammed Mustak and Swathy Krishna M, are from Mangalore University and Yenepoya University respectively while George van Driem is at the University of Bern, Switzerland.

The researchers said their findings bolster support for the hypothesis that a “Dravidian heartland” existed between Iran and the Indus Valley, much before the arrival of Indo-European languages in the subcontinent.

Such a Dravidian zone extending outside north-western India no longer exists, but its relics are still seen in the languages used by a tribe in Pakistan and a few others in India.

There are five distinct genetic components of Indian ancestry beginning with the South Asian hunter gatherer who came via the Out-of-Africa route around 60,000 years ago. Their genetic signatures are still seen among the tribes of Andaman and Nicobar island.

The hunter gatherers lived for more than 50,000 years before the Neolithic Iranian farmers arrived nearly 6000-8000 years ago. They were followed by Caspian Steppe pastoralists around 3000-4000 years ago. In addition, there were Tibeto-Burman and Austro-Asiatic groups that imparted Mongoloid features and specific traits in some of the tribes.

Scientists so far held that a mixture of these five gene pools created the genetic make-up of modern Indians. The Mangalore team has now added a sixth component into the pot.

“This doesn’t mean Koragas came from Iran. They only carry those proto-Dravidian signatures. Nearly 20% of an Indian’s genetic make-up are these proto-Dravidian genetic components. It shows those ancestors were widespread,” Das said.

The team untangle the knots by approaching the problem from two sides. While scientists traced genetic history, linguists created a unique tree to look for specific language-signatures and then matching them with the genetic footprints.

“The similarity of DNA of the Koraga and old Neolithic samples from eastern Iran, points to the Koraga language, which the authors have called ‘proto-Dravidian’, being rooted in Elamo-Dravidian. The finding that the ‘proto-Dravidian’ ancestry is found in many other groups, is consistent with our finding published in 2003 that the “Dravidian speakers, now confined to southern India, may have earlier been widespread throughout India,” commented Partha Majumder, a veteran population geneticist and former National Science Chair, who is not associated with the research.

“Their finding that the Koraga, Brahui (Balochistan) and Oraon have a shared ancestry is novel and significant,” Majumder, Emeritus Professor, Indian Statistical Institute, Kolkata told DH.

The study has appeared in the European Journal of Human Genetics.