The diversity of the South Asian population, especially in a country like India with a significant difference in ethnicity even between the north and the south zones, have intrigued scholars and ancestry enthusiasts equally. Moreover, political propaganda has led to spread of a distorted understanding about the already complex structure of the South Asian population. Till date a popular story doing rounds is that of the Aryans conquering the Indian subcontinent during the course of their extensive invasions. Another unsubstantiated claim is the out-of-India migrations.
About the study
The recent study that was preprinted by Bio-Archives in late March this year titled “The Genomic Formation of South and Central Asia” examines the ancestry of ancient Indians using genetic ancestry methods. This large scale study, that is yet to go through peer-reviewing has been co-authored by 92 experts from premium universities across the globe. The study used the genome-wide data obtained from DNA samples from 612 ancient individuals. The samples included those from Turan (a region in easter Iran which now covers Uzbekistan), Turkmenistan and Tajikistan, Kazakhstan and South Asia. Out of the 612 samples, 362 were studied and compared with the genomic data from present-day individuals including around 250 groups within South Asia.
Creation of Ancestral Groups in India
Ancient India was predominated by two major groups namely the Ancestral North Indians and the Ancestral South Indians. This forms the founding premise of the paper. The formation of these two major groups could be the result of the genetic mixing between following types of populations:
- Farming population from Iran (Iranian agriculturalists) who entered India bringing with them wheat and barley cultivation.
- The South Asian hunter gatherers, who are considered to be the oldest inhabitants of India and also known as the Ancient Ancestral South Indians.
- Inhabitants of the vast Steppes grassland extending from Central Asia to the north of Afghanistan.
- Finally the Indus Valley population that forms the key source to the ancestry of South Asians as shown by the parallel analysis of ancient DNA and genomic data from present day population of South Asia.
What are the major South Asian ancestral groups?
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The Indus Valley population
This population was first created by the population mixing between the Iranian agriculturalists and the South Asian hunter gatherers. Consequently both these populations were found to be there in the gene pool of the Ancestral North Indians and the Ancestral South Indians. The Ancestral South Indians are formed of the South Asian hunter-gatherers and the Iranian agriculturalist the South Asian hunter gatherers having a bigger share of the fraction. On the other hand, the Ancestral North Indians are a genetic mix of both the above groups along with the Steppes pastoralists.
This implies that the Indus Valley population originated from the South Asian hunter-gatherer and Iranian agriculturalist population. As the Indus Valley population moved south, they mixed with the South Asian hunter-gatherers to form the Ancestral South Indians. Similar interactions of the Indus Valley population with the Steppes pastoralist in the north created the Ancestral North Indians.
What we can infer from the study
This study is a definite blow to misconstrued versions of the origin of the South Asian population. For one, the out-of-India theory is improbable in the genetic level, since migration patterns indicate the gene flow into the South Asian region and not the opposite.
The “Ancestral South Indians” (ASI) were created from a mixing of the Indus periphery individuals with the Ancient Ancestral South Indians around 4,000 years ago. Between approximately 4,000 and 3,200 years ago populations from the Steppe grassland arrive, carrying admixture from Iranian farmers, as well as people from the Steppe. They mix with the ASI population, though a few groups, such as the Kalash, mix directly with InPe, and create unmixed “Ancestral North Indian” (ANI).
As more information comes through, like the results from the Rakhigarhi excavation site that is estimated to date back around 4,700 years, the pieces will only fit in more clearly and serve to confirm this largely unsolved puzzle.