PRAYAGRAJ: A genetic study of Assamese Indo-Aryans, published in the American Journal of Human Biology, has dismantled colonial-era racial classification and a decades-old scientific hypothesis that portrayed the Northeast as a genetic barrier isolating populations from so-called mainland India.The study, conducted by researchers from Banaras Hindu University (BHU), University of Calcutta and Hyderabad-based Centre for DNA Fingerprinting and Diagnostics, reveals continuous movement and mixing across Asia.The research team found out that the region functioned as a corridor enabling bidirectional gene flow between South Asia and East and Southeast Asia, contradicting the Barrier Hypothesis proposed by Germany’s Max Planck institutes, which argued that northeastern India isolated populations rather than connecting them.“For decades, scientists relied on the Barrier Hypothesis. Our study directly contradicts this theory, presenting evidence that the region was instead a zone of continuous interaction and exchange,” said Prof Gyaneshwar Chaubey of BHU’s zoology department.Scientists collected DNA samples from 50 Assamese people who speak Indo-Aryan languages. Of these, 12 samples underwent detailed analysis using high-resolution autosomal DNA technology, examining over seven lakh genetic markers across the genome.Unlike previous studies that relied on limited markers such as mitochondrial DNA and Y-chromosome data, this approach provided a comprehensive picture of ancestry. The team also collected samples from 1,120 people from different parts of India and Southeast Asia.The results showed Assamese Indo-Aryans possess 76% South Asian ancestry and 24% East and Southeast Asian ancestry, creating a mixed heritage highlighting centuries of migration and interaction.Assamese Indo-Aryans do not follow the typical genetic pattern seen across India. They cluster more closely with Indo-Aryan populations of Bangladesh while sharing notable genetic links with communities from the Ganga plains, such as Harijan and Kol groups.The study also found low levels of “Runs of homozygosity”, a genetic indicator that suggests high diversity and a large effective population size. This means the Assamese population has experienced continuous mixing over generations, rejecting the idea of a genetically closed population, Chaubey said.Using advanced analytical tools, researchers estimate that major admixture events occurred 55 to 61 generations – 1,650 to 1,830 years – ago. Over this period, people from different regions migrated, interacted, and settled in Assam, shaping its unique genetic identity.During the colonial era, British ethnographers classified the populations of Northeast India based on physical appearance. They labelled the inhabitants “Mongoloid”, indicating a distinct racial group separate from the “Caucasoid” or “Indo-Aryan” populations of mainland India.This classification served a political purpose by portraying the Northeast as a frontier zone biologically and culturally detached from the rest of the Indian subcontinent.“We have systematically challenged this 150-year-old narrative,” Chaubey said.
