A new genetic study has overturned a long-held scientific belief, arguing that Assam—and, by extension, Northeast India—served not as a barrier but as a bridge for human migration across Asia.
The research, led by Vanya Singh, Chandana Basu, Madhumati Chatterjee, Rakesh Tamang, and Gyaneshwer Chaubey, among others, uses high-resolution genomic data to trace the ancestry of Indo-Aryan speakers in the region.
Published in the American Journal of Human Biology, the study presents compelling evidence that challenges earlier genetic models, which viewed Northeast India as an isolated zone.
“Our study reveals a distinctive genetic profile in Assam, with approximately 76% Indian ancestry and 24% East/Southeast Asian ancestry,” said Dr Chandana Basu, a scientist at the Centre for Genetic Disorders, Banaras Hindu University.
“These findings highlight Assam’s long-standing role as a dynamic corridor enabling bidirectional gene flow between South and East/Southeast Asia, rather than as a region of isolation. This underscores the importance of the region in shaping patterns of human diversity and population history.”
For years, prevailing theories suggested that the region’s difficult terrain—marked by hills, rivers, and dense forests—limited human movement. However, the new study overturns that assumption, concluding that “Northeast India may have acted as a corridor facilitating bidirectional gene flow between South and East/Southeast Asia”.
The findings also reveal that Assamese Indo-Aryan populations do not conform to the typical South Asian genetic pattern.
Instead, they show a closer affinity to populations in Bangladesh, with researchers noting that “Assamese Indo-Aryans cluster closely with Bangladeshi Indo-Aryans, diverging from the typical South Asian genetic continuum”. This distinct genetic clustering points to deeper, long-term interactions across regions.
At the heart of the study is the idea that Assam’s population history is defined by mixing rather than isolation.
Genetic evidence suggests that major admixture events occurred around 55–61 generations ago, indicating sustained contact and exchange over centuries. The region emerges not as a frontier but as a meeting point where multiple migration streams intersect.
“Assam serves as a melting pot where various ethnicities converge, shaped by its strategic location,” the researchers note, adding that populations in the region share genetic links not only with neighbouring groups but also with Indo-Aryan populations from the Gangetic plains—suggesting multiple pathways of migration and interaction.
Another key insight is the relatively low level of genetic isolation among Assamese populations. “Low levels of runs of homozygosity suggest a high degree of genetic diversity, most likely due to admixture and a large effective population size,” the study states, reinforcing the idea of a historically interconnected population.
Highlighting the strength of the research, Prof Gyaneshwer Chaubey noted that the study’s robustness lies in its use of nearly 700,000 autosomal markers—far exceeding the limited datasets used in earlier analyses.
By combining advanced genomic tools with regional context, the study offers a more nuanced understanding of Northeast India’s human history—one shaped not by isolation, but by movement, exchange, and convergence.
In doing so, it reframes Assam’s place on the map—not as the edge of the subcontinent, but as a vital passage linking populations and civilisations across Asia.
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Roopak Goswami
Reporter, EastMojo
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