Researchers have learned new things about how people in India evolved by studying genes. They looked at DNA from over 2,700 people from different parts of India, including those from different groups like tribes and castes.
They found out that one of the main groups of ancestors in India came from ancient farmers in what’s now Tajikistan. They also found that people in India have a lot of different DNA from Neanderthals and Denisovans, who were close relatives of humans but are now extinct.
Furthermore, the researchers discovered that the main reason for the genetic differences among Indians today is a big movement of people from Africa to India about 50,000 years ago.
They wrote about their discoveries in a preliminary paper published on the bioRxiv database on February 20th.
“Many times, researchers don’t study South Asian populations enough in genetic studies,” said Elise Kerdoncuff, who led the study and works as a population geneticist at the University of California, Berkeley (UCB). “By studying Indian populations, we can learn about India’s history. Our study also gives us important information about human history in general.”
India has over 1.4 billion people and is one of the world’s most populated countries. It’s home to various groups like castes, tribes, and religious communities, making it very diverse. However, genetic studies have often overlooked Indian populations, mainly focusing on people of European descent.
To better understand India’s genetic diversity, researchers studied the genomes of thousands of older adults who participated in the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (LASI-DAD). These participants, aged 60 and above, provided blood samples for analysis.
Most Indians have ancestry from three main groups: ancient Iranian farmers, Eurasian Steppe pastoralists, and South Asian hunter-gatherers. While researchers knew how the last two groups came to India, they were unsure about the arrival of DNA from ancient Iranian farmers. Priya Moorjani, one of the study’s lead authors and an assistant professor at UCB, explained that they aimed to find out when and how this DNA reached India.
In the new study, researchers compared the DNA of modern Indians to that of people from Iran during the Neolithic to Iron Age periods. They found that the ancient Iranian-related DNA in Indian populations came from people in Sarazm during the early Neolithic.
Another analysis compared the DNA of modern Indians to that of Neanderthals and Denisovans. They discovered that, like many people outside of Africa, Indians inherited 1% to 2% of their DNA from these ancient groups. Interestingly, almost 90% of Neanderthal genes found in humans outside Africa were present in Indian genomes.
The study also revealed that most of the genetic diversity in modern Indians comes from a single major migration event from Africa around 50,000 years ago. This finding contradicts previous archaeological studies suggesting that modern humans settled in India earlier, even before the eruption of the Toba volcano around 74,000 years ago.
There are still many unanswered questions, especially about the people living in India 50,000 years ago. For instance, it’s uncertain whether Neanderthals and Denisovans lived in South Asia or if modern humans met them further east in Eurasia. These genes might have been brought to India by migrating humans.
“By combining findings from other fields like archaeology and linguistics, I hope we can better understand our evolutionary history,” Moorjani added.
