Modern South Asians descend from a mix of farmers, steppe pastoralists, and hunter-gatherers, and show genetic links to the Bronze-Age Indus Valley Civilization, according to two studies published yesterday (September 5) in Science and Cell. Analyzing hundreds of ancient genomes, researchers traced the history of South and Central Asians over thousands of years to estimate the timing of demographic and cultural movements such as migrations and the adoption of farming.
In the Science paper, an international team of researchers analyzed DNA from 523 ancient humans who lived over the last 8,000 years. The results indicate that after the decline of the Indus Valley Civilization, which practiced agriculture and flourished across what is now India and Pakistan from 3300 BCE until around 1300 BCE, some members of the civilization mixed with hunter-gathers from Southeast Asia to give rise to a people known as the Ancestral South Indians.
Other descendants of the Indus civilization mixed with steppe pastoralists—who likely brought with them early versions of the Indo-European languages now spoken in the Indian subcontinent—to give rise to the Ancestral North Indians. The mixing of the north and south populations of ancestral Indians since then gave rise to many of the diverse ethnic groups now living in South Asia.
In the Cell paper, researchers analyzed the DNA of a single individual who died more than 4,000 years ago and was buried at Rakhigarhi, an Indus Valley Civilization site in northern India. Sequences from this individual, who genetic analyses suggested was female, showed evidence of ancestry from Southeast Asian hunter-gatherers and ancient Iranians, but not from more-recent Iranian farmers or steppe pastoralists.
This study throws new light on the origin of farming in South Asia, Harvard University’s David Reich, a coauthor on both papers, tells ScienceAlert. “A mainstream view is that farming came to South Asia through the large-scale . . . movement of Iranian farmers,” he says. But the absence of Iranian farmer DNA in the Indus Valley individual suggests instead that farming in South Asia either arose on its own, or was brought to the area through the cultural transmission of ideas without interbreeding between local and Iranian farmer populations.
Gyaneshwer Chaubey, a biological anthropologist at Banaras Hindu University in Varanasi who wasn’t involved with the study, tells Science that “it seems likely there were independent advents of farming.” Scientists will have to carry out more archaeological and genetic work to get a clearer picture of how this happened, he adds. “The findings from the study are extremely exciting, but this is just the beginning of the story.”
Vasant Shinde, an archaeologist at Deccan College in Pune in India and a study coauthor on both papers, says in a press statement that the team hopes to learn more about what happened to the Indus Valley Civilization.
“The insights that emerge from just this single individual demonstrate the enormous promise of ancient DNA studies of South Asia,” he says. “They make it clear that future studies of much larger numbers of individuals from a variety of archaeological sites and locations have the potential to transform our understanding of the deep history of the subcontinent.”
Catherine Offord is an associate editor at The Scientist. Email her at firstname.lastname@example.org.