Subhra Priyadarshini / CSE , S

Nicobarese (left) and khasis s

scientists now have firm genetic evidence that early Austro-Asiatic settlers in India, believed to be the oldest, migrated from here to south-east Asian countries and populated them. These early tribes migrated out of the country through the north-eastern states, a study published in BMC Evolutionary Biology (March 27 issue), says.

Genetic data has revealed that ancestors of the present day Austro-Asiatics could be one of the earliest inhabitants of India. Also, tribes like Munda and Santhal from Chotanagpur plateau, Khasi from Meghalaya and Nicobarese from Andaman and Nicobar are genetically linked, despite their apparent ethnic differences. These tribes also have links with the Austro-Asiatic speakers of south-east Asia, the study says.

Aiding medicine
Lead author of the study B Mohan Reddy of the Indian Statistical Institute, Hyderabad, told Down To Earth that the study has significant implications in medical genetics as well.

“These communities might share the same genetic variation responsible for a particular disease. If we find this variation—although it is not all that easy to find—we may pinpoint them similarly in other Austro-Asiatic communities.”

Austro-Asiatics, exclusively represented by tribes have a substantial presence in south-east Asia. A team of research students lead by Reddy, in collaboration with Centre for Cellular and Molecular Biology, Hyderabad analysed dna samples for y-chromosome variation in 1,222 males from 25 Indian Austro-Asiatic tribes—by far the most exhaustive coverage of this linguistic family.

They covered all the three branches of Austro-Asiatic tribes—Mundaris (Mundas), Khasi-Khmuics (Khasis) and Mon-Khmers (Nicobarese and Shompens). Against this data, they compared previously published data on 214 populations from Asia and Oceania.

The researchers reported that a genetic family tree or haplogroup (om95) originated in the ancestors of the Indian Austro-Asiatic population (particularly in the Mundaris) around 65,000 years ago. The age of this haplogroup is estimated to be much lower.

No study had genetically linked the different groups of Austro-Asiatics till now. “Nobody could have thought that Mundas could be linked to Khasis and Nicobarese and eventually to the Austro-Asiatic groups of south-east Asia. We have also suggested, unambiguously, that these groups are genetically different from the predominant Indo-European and Dravidian groups, which means that Austro-Asiatics had a distinct origin,” he says.

The results indicate that contrary to prevalent notion, the Austro-Asiatics moved from India to south-east Asia via the north-east Indian corridor and not vice-versa. After expanding in south-east Asia, some of them moved to Nicobar Islands, possibly much later.

Paternal property
“The Y-chromosome is transmitted only from father to son. Any study based on this chromosome reflects the genetic demography of males only. In our study we saw a strong genetic link between the Austro-Asiatic groups based on y-chromosome. This link was not quite apparent in our preliminary analysis of mitochondrial dna (mdna), which is passed on from mother to daughter and chronicles maternal genetic history,” Reddy said.

They concluded that the migration was primarily male driven. The group, in collaboration with Vikrant Kumar, Reddy’s PhD student with the Genome Institute of Singapore, is now finalising a paper based on analyses of the m dna data which may be published soon.

These new findings corroborate recorded linguistic hypotheses, which suggest that ancestors of Austro-Asiatics originated in India and migrated to south-east Asia.

In 1974, linguist Gerard Diffloth classified Austro-Asiatics on the basis of languages. The Indian subcontinent is inhabited by four major linguistic groups—Austro-Asiatic, Dravidian, Indo-European and Tibeto-Burman. The Austro-Asiatic family has the greatest divergence in their nouns and some other linguistic features. So it is considered to be the oldest of the four linguistic families.

Says professor Vaishna Narang of the Centre for Linguistics at Jawaharlal Nehru University,” Linguists have long had several hypotheses on Austro-Asiatics migrating to south-east Asia. Now we have scientific evidence to back them.”