What can our DNA tell us about where Indians came from? How far back can scientists trace human migration? And can artificial intelligence help decode the genetic history of one of the world's most diverse populations?
For Dr Kumarasamy Thangaraj, a geneticist at the CSIR-Centre for Cellular and Molecular Biology (CSIR-CCMB), Hyderabad, these questions have shaped more than three decades of scientific research. A CSIR Bhatnagar Fellow, Dr Thangaraj has worked extensively on population genetics and human evolution. His research has helped trace the ancestry and migration of Indian populations, including studies of the Andaman tribal populations that provided evidence for an early modern human migration out of Africa through a southern coastal route about 65,000 years ago.
Born in Cheyyur, Tamil Nadu, Dr Thangaraj spent his early years in a village environment before moving to Chennai for higher education. He joined CCMB in Hyderabad in 1993 and has since built a career studying the genetic history of Indian populations and the health consequences of endogamy.
His work has also examined how long-term endogamy has shaped the genetic structure of Indian populations and contributed to the prevalence of population-specific genetic disorders. He has published more than 300 research papers, with his work appearing in leading scientific journals.
In 2026, Dr Thangaraj was conferred with the Padma Shri by the government of India for his scientific contribution. He was also a recipient of the Rashtriya Vigyan Puraskar–Vigyan Shri in 2025. Other honours he has received include the CSIR-Bhatnagar Fellowship, J C Bose National Fellowship, Raman Research Fellowship and Sun Pharma Research Award in Medical Sciences, among others.
He is also an elected Fellow of the Indian National Science Academy, Indian Academy of Sciences and National Academy of Sciences, India.
In an interview with The New Indian Express, Dr Thangaraj discusses India's genetic ancestry, the Andaman populations, the limits and possibilities of DNA evidence, the health implications of endogamy, and how AI could help scientists analyse the country's vast genomic diversity.
1. You come from a village in Tamil Nadu. What sparked your interest in biology and genetics first?
I was born and brought up in Cheyyur, a village in Tamil Nadu located between Chennai and Puducherry. I completed all my schooling in the village before moving to Chennai for my undergraduate studies and later pursuing higher education, including my PhD. Having spent my early years in a village, I had the opportunity to spend a great deal of time around plants, animals, and diverse ecosystems. This naturally sparked my interest in the life sciences, particularly genetics.
Growing up in a village, I often heard people say that a child has a nose like their mother’s or hair like their father’s. They may not have known the science of genetics, but they understood, through everyday observation, that certain characteristics are passed from parents to their children. The same principle can be seen in plants. When a plant produces a better yield, farmers often preserve its seeds and use them for the next season. These simple, everyday practices are all examples of how genetic characteristics are transmitted from one generation to the next.
2. What were some of the major milestones in your scientific career, and what led you to focus on the genetic history of Indian populations?
My lab has been working on human evolution and medical genetics for more than three decades. One of our major areas of work was studying the enigmatic tribal populations of Andaman and Nicobar islands. There are four tribal groups in the Andaman Islands, including the Great Andamanese, Onge, Jarawa and Sentinelese. The Sentinelese continue to live in isolation, so researchers cannot approach them. We had the opportunity to collect samples from three Andaman populations. When we analysed their mitochondrial DNA and other genetic markers, we found evidence that these tribal populations migrated from Africa and reached the Andaman and Nicobar Islands around 65,000 years ago through a southern coastal route. Some groups remained in South Asia, while others continued towards Australia.
3. What does genetic evidence tell us about when and how modern humans reached the Indian subcontinent after leaving Africa?
The evidence indicates that modern humans reached this region around 65,000 years ago. Some groups settled in southern parts of the Indian subcontinent, some moved towards the Andaman and Nicobar Islands, and others eventually migrated towards Australia. There are genetic affinities between some present-day populations in South India, the Andaman region and Aboriginal Australians, suggesting connections with these very early migrations.
4. How can the DNA of people living today act as a record of migrations that happened thousands of years ago?
Mutations occur naturally in DNA, and some of these changes can accumulate over generations. When a genetic change is inherited and persists in a population, it can be passed from one generation to the next. By studying these genetic variations and comparing them across different populations and with ancient DNA, we can infer genetic relationships and reconstruct aspects of population history.
For example, if we sequence an ancient DNA sample that is 50,000 years old and compare it with genomes from contemporary populations, we can identify genetic changes that have accumulated over the intervening 50,000 years. By examining these genetic differences and shared patterns of variation, we can gain insights into the relationships among populations, as well as their evolutionary history and migration patterns.
5. Your research has reshaped our understanding of the ancestry of present-day Indians. What were some of the most significant findings?
There are several important findings. One is that genetic evidence indicates that the earliest modern human populations in the region were connected to out-of-Africa migrations. Our research also challenged the idea of an Aryan invasion in which a population from outside India arrived and displaced or pushed existing populations towards the south. Genetic evidence does not support that simplistic model. Another important finding is that present-day Indians have evolved from two ancient ancestries — Ancestral South Indian (ASI) and Ancestral North Indian (ANI) — and these two ancestries admixed around 2,000–4,000 years ago. Today, populations across India share genetic ancestry from both ASI and ANI, irrespective of caste or tribal identity. This also illustrates the idea of “unity in diversity” from a genetic perspective. There is also an important medical dimension. For roughly the last 2,000 years, many Indian populations have practised endogamy — marriage within the group. Because of this, certain mutations can become more frequent within particular populations, and some of these may be responsible for population-specific diseases.
6. India has extraordinary genetic diversity. How much of this diversity reflects ancient migration, later population mixing and isolation?
Population-specific marriage practices have existed for a very long time. The caste system, as we understand it today, developed later, but endogamy existed before the present-day caste identities emerged. Communities may have different names and identities today, but these identities do not necessarily represent separate ancient populations. Genetic studies show that different Indian populations have shared ancestry and have experienced admixture at different points in history. Therefore, genetics should not be used to assume that present-day caste or community identities correspond directly to distinct ancient biological populations.
7. AI is increasingly being used to analyse large genomic datasets. Could it help identify migration patterns or ancestral relationships that conventional methods may have missed?
Geneticists have been using various statistical tools to analyse genetic data. What we now call artificial intelligence provides opportunities to analyse large datasets much more efficiently and quickly. However, AI itself does not provide the final scientific conclusion. Scientists have to interpret the results and draw conclusions.
8.What are the risks of AI producing misleading conclusions from genetic data?
There are risks. If something goes wrong during analysis, AI or any computational method can produce incorrect information. That is why we don't rely on a single method. We use multiple methods or approaches. If two or three independent methods produce consistent results, we have greater confidence in the finding. If one method produces a different result, that needs to be investigated. Ultimately, scientists have to validate and interpret the results.
9. What are the biggest unanswered questions about Indian genetic history that new genomics technologies and AI could help address?
India is inhabited by 4,635 populations. Since these populations have been practising endogamy for 2,000 years, each population is expected to acquire population-specific mutations. Some of these may be associated with genetic diseases, some with responses to commonly used drugs, some with adaptation to the environment, and some may provide resistance or susceptibility to infectious diseases. We have now sequenced the whole genomes of 10,000 individuals from 83 populations and identified 130 million variations. This means that we need to sequence every single population to understand their health and design precision medicine. Therefore, we need to generate genetic data from every single population. Once we generate sufficiently large datasets, AI and other computational tools can be used to analyse them and identify patterns that may otherwise take a very long time to detect. AI alone cannot generate the data; it can only help us analyse the data.
10. After decades of studying India's genetic history, what is the one thing you want the public to understand about where Indians came from — and what our DNA can and cannot tell us about our ancestry?
One thing is very clear from our studies: we all descended from early humans who migrated out of Africa. Present-day populations have mixed genetic ancestry. Genetically, we are all connected, supporting the idea of unity in diversity. Genetic testing can help identify disease-causing mutations in appropriate situations. Once a mutation is identified, there can be opportunities for counselling and preventive measures to reduce the risk of passing certain genetic conditions to the next generation.