The Indian population is genetically one of the most diverse in the world, but it remains underrepresented in global data sets. In a study published in the Cellular Review CellThe researchers analyzed genomic data of more than 2,700 people from all over India, capturing the genetic variation of most geographic regions, linguistic groups and communities. They found that most of the ancestors of the modern Indian people date back to Neolithic Iranian farmers, the Eurasian steppe pastors and the southern Asian hunters.
“This study fills a critical gap and reshapes our understanding of the way in which ancient migration, archaic mixture and social structures shaped Indian genetic variation,” said the main author Priya Moorjani of the University of California in Berkeley. “The study of these sub-populations allows us to explore how anchored ancestry, geography, language and social practices interacted to shape genetic variation. We hope that our study will provide a more in-depth understanding of the origin of functional variation and will inform precision health strategies in India.”
The researchers used data from the study of longitudinal aging in India, a diagnostic evaluation of dementia (LASI-DAD) and generated sequences of the whole genome of 2,762 people in India, including people who spoke a range of different languages. They used these data to rebuild India’s evolutionary history in the past 50,000 years on a large scale, showing how history has an impact on adaptation and disease in current Indians. They have shown that most Indians have ancestral ancestral group ancestors: Neolithic Iranian farmers, Eurasian steppe pastors and South Asian hunters.
“In India, genetic and linguistic variations often go hand in hand, shaped by ancient migration and social practices,” explains the main author Elise Kerdoncuff from UC-Berkeley. “Ensure the linguistic variation between people whose genomes we include, which helps prevent biased interpretations of genetic models and discover the functional variation linked to all the main communities to shed light on evolutionary research and future biomedical surveys.”
One of the key objectives of the study was to understand how the history of the complex population of India shaped the genetic variation linked to the disease. In India, many subpopulations have an increased risk of recessive genetic disorders, which is largely due to historical isolation and marriage within communities.
Another emphasis was on the impact of the archaic ancestry of hominins – in particular, Neanderthal and Denisovan – on sensitivity to diseases. For example, some of the genes inherited from these archaic groups have an impact on immune functions.
“One of the most striking and unexpected discoveries was that India is home to the greatest variation in Neanderthal ancestry among non-Africans,” said co-directed author Laurits Skov, also UC-Berkeley. “This allowed us to rebuild around 50% of the Neanderthal genome and 20% of the genome of Denisovan of Indian individuals, more than any other previous study of archaic ancestry.”
A constraint of this work was the limited availability of the old DNA of South Asia and the South Center. As older genomes become available, researchers will be able to refine this work and identify the source of the Neolithic Iranian farmer and ancestry linked to the pastoralist of the steppe among contemporary Indians. They also plan to continue to study the Lasi-Dad cohort to allow a more in-depth examination of the source of genetic adaptations and variants of disease across India.