Indians' ancient ancestry lies with Iranian farmers

Genomes from people across modern-day India shed light on 50,000 years of evolutionary history

Researchers analysed data from 2,700 people from across India. Getty Images

A genetic study of modern-day Indians has revealed their ancestry can be traced back to Neolithic Iranian farmers, Eurasian Steppe pastoralists and South Asian hunter-gatherers.

Researchers analysed data from 2,700 people from across India, capturing genetic variation based on geography, linguistic groups and communities. The results could help inform health strategies for the country.

How Indian ancestry can be traced back to a migration out of Africa around 50,000 years ago, after which humans inter-bred with Neanderthals and Denisovans and then spread throughout Eurasia. UC Berkeley

“This study fills a critical gap and reshapes our understanding of how ancient migrations, archaic admixture, and social structures have shaped Indian genetic variation,” said senior author Priya Moorjani of the University of California, Berkeley, who pointed out that even though India’s population is one of the most diverse in the world, it is underrepresented in global data sets.

“Studying these subpopulations allows us to explore how ancient ancestry, geography, language, and social practices interacted to shape genetic variation.”

They used this data to reconstruct the evolutionary history of India at fine scale, showing how history affects adaptation and disease in present-day Indians.

Modern-day Indians' ancestry can be traced to Neolithic Iranian farmers. Getty Images

The UC Berkeley team found that most of the genetic variation in India can be explained by a single migration of humans out of Africa about 50,000 years ago. These populations interbred with now-extinct relatives – Neanderthals and Denisovans – and then spread throughout Europe and Asia, including India. As a result, Indians and Europeans both carry roughly equal amounts of Neanderthal genes – between 1 per cent and 2 per cent of the entire genome.

“Potentially, there were earlier waves out of Africa to India, but it’s likely that those groups either did not survive or left little genetic impact on today’s populations,” said Elise Kerdoncuff, a former UC Berkeley postdoctoral fellow and one of two lead authors of the paper.

One of the main goals of the study, published in the journal Cell, was to understand how India’s complex population history has shaped genetic variation related to disease. In India, many subpopulations have an increased risk of recessive genetic disorders, which is due largely to historical isolation and marrying within communities.

Another focus was on how Neanderthal and Denisovan ancestry could make people susceptible to certain diseases. Surprisingly, Indians have a greater variety of Neanderthal DNA segments than other populations around the world.

“One of the most striking and unexpected findings was that India harbours the highest variation in Neanderthal ancestry among non-Africans,” says co-lead author Laurits Skov, also of UC-Berkeley. “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.”