Rare ancient DNA offers window into South Asian civilization 5,000 years ago

In the millennia BC, beginning about 5,000 years ago, great civilizations flourished in Eurasia and North Africa. The ancient societies of Mesopotamia and Sumer in the Middle East were among the first to introduce written history; the Old, Middle, and New Kingdoms of Egypt established complex religious and social structures; the Xia, Shang, and Zhou dynasties ruled China Continuously improving community and technology. But another, lesser-known civilization flourished in the Indus Valley, across much of modern Afghanistan and Pakistan, and into northwestern India.

The Indus Valley Civilization (IVC), also known as the Harappan Civilization, is shrouded in mystery after an archaeological site in Pakistan, mainly because scholars have not yet Find out the meaning of the Harappan language, which is made up of fragmented symbols, pictures and other texts. Archaeological evidence has given researchers some insight into the daily lives of the Harappan people, but because of the deterioration of genetic material in hot and humid regions, scientists have struggled to piece together evidence from ancient DNA in the IVC until now.

For the first time, scientists have sequenced the genome of a person from 2600 BC to 1900 BC, the Harappan or Indus Valley Civilization that peaked in what is today the Indo-Pakistan border region, 4,500 years ago. Traces of DNA from a woman found in a cemetery years ago were painstakingly recovered from ancient skeletal remains, giving researchers a window into one of the world's oldest civilizations. This work, along with a comprehensive analysis of ancient DNA across Eurasia, also raises new questions about the origins of agriculture in South Asia.

The ancient Harappan genome was sequenced and described in the journal Cell and compared with the DNA of modern South Asians, revealing that the IVC people are the ancestors of most Indians. Both modern South Asian DNA and Harappan genes contain a mix of ancient Iranian DNA and small amounts of Southeast Asian hunter-gatherer ancestry. "Among IVF individuals, such ancestors are the primary source of ancestry in South Asia today," co-author David Rich, a geneticist at Harvard Medical School, said in a statement. ". "This discovery directly links the people of today's South Asia to the Indus Valley Civilization. ” are bones analyzed in ancient DNA research and are associated with typical Indus Valley Civilization burials, illustrating the typical north-south orientation of IVC burials. (Vasant Shinde/Deccan College Graduate School)

The genome also holds some surprises. Steppe pastoralists spread across the vast grasslands of Eurasia from contemporary Eastern Europe to Mongolia, and their genetic relationships with steppe pastoralists are ubiquitous among other peoples in South Asia and Europe and across the continent. But there are no steppe pastoralists among the individuals of the ancient Indus Valley. of DNA, suggesting that the similarities between these nomadic pastoralists and modern groups arose due to migration after the decline of the IVC.

These findings influenced how and where the Indo-European language family evolved. Theory of when widespread in the ancient world While the same ancestors of modern South Asians and early Iranian farmers fueled the idea of ??agriculture migrating from the fertile crescent of the Middle East to Indo-Pakistan, ancient Harappan genes No contribution of this lineage has been shown, suggesting that agriculture spread through the exchange of ideas, rather than large-scale migration, or even emerged independently in South Asia

" "The archaeological and linguistic work is really at the forefront of our research process," said Vagheesh Narasimhan, a genomicist at Harvard University and co-author of the new study. "These projects bring a new set of genetic evidence to this process." , an attempt to demonstrate the possible impact of human activity as part of two major cultural changes, agriculture and language,

This well-planned megacity included sewers and water systems, and extended into Mesopotamia long-distance trade network. But despite its glory days, this civilization was unknown to modern researchers until 1921, when excavations at Harappa began to uncover an ancient city. The Harappans have maintained something of a mystery ever since, leaving behind extensive urban ruins and a mysterious language of symbols and paintings, but few other clues to their identity. What ultimately befell the Harappan civilization is also unclear, although changes in climate are thought to be part of its decline.

This map depicts the geographical span of the Indus Valley Civilization (IVC), showing the location of Rakhigarhi (blue) and other important IVC sites (red), as well as sites from other archaeological cultures (other colors) to the north and west. The yellow labels show two sites where a handful of buried individuals yielded ancient DNA matching the Rakhigarhi individuals. (Vasant Shinde/Deccan College Graduate School)

Scientists have had a notoriously difficult time recovering ancient DNA in South Asia, where subtropical climates often make genetic preservation impossible. It took a lot of time to extract the genome from the remains found in the necropolis of Rakhigarhi, the Harappan people's largest city in the modern Indian state of Haryana. Scientists collected powder from 61 bone samples, but only one contained trace amounts of ancient DNA. This sample was sequenced as much as possible, producing 100 different DNA fragments***, called libraries, each of which was too incomplete to do its own analysis, but we were lucky that it produced enough DNA to then perform high-resolution population genetics analysis," Narasimhan said. "I think this paper is a technical success story," he added, noting that the method holds promise for obtaining DNA from other challenging regions. .

A single sample is not representative of the broad population that once included a million or more people, but a related study published today in the journal Science provides a broader regional context that includes Nasdaq. Several of the same authors, including Rashimhan and Reich, along with dozens of international collaborators, produced the largest study of ancient DNA ever published, including genetic sequences from 523 ancient humans from far away. Iron Age people from the Eurasian steppes, eastern Iran and the Swat Valley of modern Pakistan found that among many genetically similar individuals there were a few outliers with ancestral types similar to those around them. The species are completely different.

Eleven such individuals found in sites in Iran and Turkmenistan may be related to the Harappan civilization. In fact, some of these isolated individuals were buried in the Artifacts with cultural ties to South Asia strengthen the case that they are linked to the IVC

"This leads us to hypothesize that these specimens are immigrants, possibly even first-generation immigrants from South Asia," Narasimhan said. said. The IVC genome from Rakhigarhi shows strong genetic similarity to 11 genetic outliers in large-scale studies of ancient humans, supporting the idea that these individuals ventured into the Middle East from the Harappan civilization. Collected together, they roughly represent the ancestors that existed in (South Asia) at that time. ” This mid-Bronze Age tomb in Dali, Kazakhstan (c. 1700 B.C.) was looted in ancient times and human remains were haphazardly piled outside the tomb cist. DNA extracted from these remains helped trace steppe ancestors from B.C. The spread to eastern and southern India from 2000 to 1500 BCE (Michael Frachetti)

The first evidence of agricultural research comes from the Fertile Crescent as early as 9500 BCE, Many archaeologists have long believed that the practice of growing crops was brought to South Asia by immigrants from the Middle East, and early DNA research seemed to support this idea, as today's South Asians have significant Iranian ancestry. "I really found their analysis very exciting," said Priya Moorjani, a population geneticist at UC Berkeley. "They looked at ancient DNA samples from Iran at different time scales and tried to link South Asians to Iran. The first farmers of the Fertile Crescent appeared to have made little genetic contribution to the South Asian population, new analysis shows. "However, similar farming practices emerged in South Asia around 8000 BC," said Moorjani, co-author of the Demographic Study of South and Central Asia. "As we get more ancient DNA, we can start to build a more detailed picture of how agriculture spread around the world. We're learning that, like everything else, things are very complex.

If agriculture did spread from the Fertile Crescent to modern India, it was likely that it spread through the exchange of ideas and knowledge, a cultural transfer, rather than a major migration of western Iranian farmers themselves . In South Asia, on the other hand, agriculture could develop independently, as agricultural practices began to sprout in many parts of Eurasia during this period.

There are other mysteries about the ancient IVC ancestors, too. This civilization was the largest source population for modern South Asians and Iron Age South Asians, but it lacked the steppe pastoralist ancestry common in later eras. "Just as in Europe the ancestors of the steppe pastoralists did not appear until the Bronze Age, the same is true in South Asia," Narasimhan said. "This evidence therefore provides information about the arrival time of this ancestral type, and their movement is similar to the linguistic systematics of the Indo-European family of languages, which are spoken today in places from Ireland to New Delhi."

The author suggests that Indo-European languages ??may have reached South Asia via Central Asia in Eastern Europe during the first half of 1000 BC, a theory supported by some genetic studies of the similarities between Indo-Iranian and Baltoslav languages. sex.

Narasimhan hopes that more genetic data will help solve this ancient mystery, especially by exploring where the DNA matches or diverges from findings from other language families. "We are trying to study when and how archaeological cultures are linked to a particular genetic ancestor, and whether there is a linguistic link." "To understand human history, you really need to integrate these three strands."