The second study focuses on just a single genome from the Indus Valley civilization: I6113, a woman who died more than 4,000 years ago. Her skeleton was the only one—out of more than 100 samples the researchers tested from 10 different Indus Valley–civilization sites—that yielded ancient DNA, but even then it was contaminated and of poor quality. “We had to squeeze, squeeze, squeeze the sample really hard, more than we’ve done in any other sample we’ve ever tried,” says Reich, who is also a senior author of the second paper. The team ultimately tried to sequence DNA from I6113’s ear bone more than 100 times, each time yielding a tiny dribble of genetic data. That I6113 gets her own paper is a testament to both the technical difficulty of sequencing her DNA and the importance of the Indus Valley civilization. Even before publication, rumors were swirling in India about what the ancient DNA would show, and how it would play into the politics of the Hindu-nationalist ruling party.

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What’s intriguing about I6113’s DNA is what she lacks: any of the steppe ancestry that is widespread in contemporary South Asians. Instead, she appeared to have a mix of Southeast Asian hunter-gatherer and Iranian-related ancestry.

The two studies piece together a history of how the people of the Indus Valley civilization are related to South Asians today. After the decline of the civilization 4,000 years ago, people with a genetic makeup similar to I6113 mixed with people of Southeast Asian hunter-gatherer ancestry to form what has been called Ancestral South Indians. From 4,000 to 3,000 years ago, other people descended from the Indus Valley civilization mixed with people of steppe-pastoralist ancestry, who likely brought horses and the Indo-European languages now spoken on the subcontinent, to form a group that has been called Ancestral North Indians. These two ancestral groups then mixed as well, giving rise to the great diversity of ethnic groups in South Asia. Go back far enough, and both sides trace to the Indus Valley civilization, which appears to be the single largest source of ancestry for modern South Asians.

The team studying I6113 noticed something intriguing about the Iranian-related portion of her ancestry, too. It appears to date to before the advent of farming in the Fertile Crescent. This suggests that farming did not, as many have thought, spread to South Asia through the migration of people from the Near East. It may have arisen independently in South Asia or spread through cultural contact.

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Of course, this is a lot to rest on a single genome. “That would be like taking a single sample from Tokyo and trying to generalize about the whole ancestry of Japan,” Reich admits. But the team’s confidence in its results was bolstered when the researches found that I6113 was genetically similar to 11 people from the 523-genome paper who were buried not in South Asia, but in what is now Iran and Turkmenistan. These 11 people were also “outliers” in their own burial sites. The team thinks they may have been migrants or the children of migrants from the Indus Valley civilization. Archaeological evidence suggests people traveled between these regions as well.