Most Indians descended from 3 ancient populations in Iran, Eurasia, South Asia: Study

New Delhi: Analysing present day genomes collected via an ageing study, researchers have showed that most Indians descend from three ancestral groups: Neolithic Iranian farmers, Eurasian Steppe pastoralists, and South Asian hunter-gatherers.

Neolithic, also known as 'New Stone Age', which featured the development of agriculture and polished stone tools.

The study "fills a critical gap" in how historic migration and social structures helped shape India's populations -- genetically the most diverse in the world, yet underrepresented in global datasets, the team from the University of California-Berkeley (US), All India Institute of Medical Sciences, New Delhi, among other institutes, said.

They reconstructed the evolutionary history of India over the past 50,000 years at fine scale using whole genome sequences of 2,762 linguistically diverse individuals from the Longitudinal Aging Study in India, Diagnostic Assessment of Dementia (LASI-DAD).

The findings, published in the journal Cell, will also help reveal the source and dynamics of how historic populations in the subcontinent adapted, along with their disease vulnerability, the authors said.

"This study fills a critical gap and reshapes our understanding of how ancient migrations, archaic admixture, and social structures have shaped Indian genetic variation," senior author Priya Moorjani, from the University of California, Berkeley, said.

"Studying these sub-populations allows us to explore how ancient ancestry, geography, language, and social practices interacted to shape genetic variation. We hope our study will provide a deeper understanding of the origin of functional variation and inform precision health strategies in India," Moorjani said.

Among the world's non-Africans, Indians were found to harbour the highest diversity as ancestors of Neanderthals -- humans' closest extinct relative who lived in Europe and southwestern to central Asia about 400,000 to 40,000 years ago.

"This allowed us to reconstruct around 50 per cent of the Neanderthal genome and 20 per cent of the Denisovan genome from Indian individuals, more than any other previous archaic ancestry study," co-lead author Laurits Skov, from the University of California-Berkeley, said.

Denisovans were another distinct group of ancient humans, closely related to Neanderthals, but primarily lived in Asia. Studies suggest the group to have gone extinct about 20,000 to 50,000 years ago.

Part of the genes inherited from both these ancient human groups have an impact on immune functions, which can help understand Indians' disease vulnerability better, the researchers said.

They added that the analysis was constrained by a limited availability of ancient DNA from South and Central Asia.

As more ancient genomes become available, we will be able to refine this work and identify the source of Neolithic Iranian farmer and Steppe pastoralist-related ancestry in contemporary Indians, the team said.

We plan to continue studying the LASI-DAD cohort to enable a closer look at the source of the genetic adaptations and disease variants across India, they said.