Hyderabad: A new study has found that the Tibeto-Burman populations of Bangladesh carry substantially higher mainland Indian ancestry component than either northeast Indian or Southeast Asian Tibeto-Burman speaking people.
"We carried out a detailed genetic analysis of three major tribal populations (Chakma, Marma and Tripura) from Bangladesh, who speak a branch of Tibeto-Burman language and compared them with our large data-set from India and Southeast Asia," Kumarasamy Thangaraj of CSIR-Centre for Cellular and Molecular Biology (CCMB) said here.
"We observed that the Bangladesh Tibeto-Burman populations carry substantially higher mainland Indian ancestry component than either northeast Indian or Southeast Asian Tibeto-Burmans speaking people," he said.
A team of scientists led by Thangaraj, in collaboration with Nurun Nahar Gazi Sultana and her team from University of Dhaka, have studied the origin and affinity of Bangladeshi tribal populations for the first time using all genetic systems (mtDNA, Y chromosome and autosomes) that are used for population-based studies.
Bangladesh is bordered by eastern India in west, northeastern India in north and east and it also shares a narrow boundary with Myanmar on the southeastern rim.
Its geographical placement epitomised it as an important linguistic contact zone, Thangaraj said.
Although the Indian populations inhabited around Bangladesh have been fairly studied, the tribal populations living in the coastal as well as Chittagong hill tract regions have not been studied to understand their origin and relationship, he said.
The results of the collaborative study have been published in international journal PLOS ONE and suggested several leads to the debate over the possibility, probable location and ways of human movements from India and Myanmar to Bangladesh.
"The genetic studies so far on south and southeast Asian populations suggested that the expansion of Tibeto-Burman population happened very recently in India from southeast Asia, while we have found a more complex population history of south Asian Tibeto-Burman speakers than it was suggested before and our study stretches the time of migration from mid Holocene to early holocene," the CCMB quoted Gyaneshwar Chaubey, co-author and a molecular biologist at the Estonian Biocentre, Tartu, Estonia, as saying.
According to the authors, "The age of Y chromosal major haplogroups, ranging from 14-18 Kya, suggests that they arose before the differentiation of any language group and at approximately the same time.
"Contrary to the previous scenario proposed for colonisation of northeast India as male founder effect has occurred within the past 4,000 years, we suggest a significantly deep colonisation of this region.
"Unlike Austroasiatic (Munda) speakers of India, we observed equal roles of both males and females in shaping the Tibeto-Burman expansion in Southern Asia," CCMB quoted Nurun Nahar Gazi Sultana as saying.
"Such collaborative studies are always useful in determining the role of people of India in early human migrations," CCMB Director Mohan Rao said.