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The Extraordinary Genetic Diversity Of Indians explained

Updated: Mar 15

CP Rajendran, Adjunct Professor, National Institute of Advanced Studies, Bangalore, India.



In a research paper, published as a preprint on bioRxiv, a group of researchers led by Elise Kerdoncuff of the University of California reconstructs the origin of Indian ancestry based on the genome sequencing studies of individuals representing various geographic regions including tribal and caste groups. Their data based on about 2700 individual samples reveal that the Indians mostly derive their ancestry from three fundamental ancestral groups: one, ancient Iranian farmers, two, Eurasian steppe pastoralists, and three, south Asian hunter-gatherers.


Further, in deep time scales, they also Indians shared their genetic ancestry with the Neanderthals and Denisovans. The last-mentioned clades belong to extinct human subspecies, living about 40,000 years ago. This finding came as a total surprise. The researchers also found that Indians have ‘the largest variation in Neanderthal ancestry’ and much of the genetic variation in Indians stems from a single major migration out of Africa about 50,000 years, ago. This is surprising because no fossil evidence of those archaic cousins has been found so far in India. Researchers, therefore, do not rule out the possibility that close kin–marrying traditions prevalent in India may have facilitated Neanderthal DNA from fading out in Indian genes compared to the human genome sequences available from other continents.


The results from this study are another nail into the coffin for the theory of Indian ancestry based on the premise that the Vedic Aryans were indigenous to the Indus Valley region and had been active for more than 20,000 years, who, according to their interpretation, became the progenitor of the culture across the world by extending westward.


This ‘out-of-India’ theory flies in the face of all the available evidence generated by a spectrum of scientific and sociological studies. Indigenous Aryanism and the Out of India Theory is the belief that is propagated as an alternative to the migration model, which considers the Pontic-Caspian steppe of Central Asia as the origin of the Aryans and the Indo-European language.


The results of this study are also supported by two scientific papers published in the journals Cell and European Journal of Human Genetics in 2019 on early settlers of Central and South Asia, describing the archaeogenetics of the early settlers of Central and South Asia.


They chart the genetic trail of the hunter-gatherers, Iranian farmers, and pastoralists from the Pontic-Caspian steppes, and how they may have intermingled to become the makers of some of the world’s earliest civilisations. One of the papers titled “A Harappan Genome Lacks Ancestry from Steppe Pastoralists or Iranian Farmers”, dated 17 October 2019 authored by Vasant Shinde and others, tracked the lineage of the people who settled the Indus Valley through genomic analysis.


Experts generally agreed that during the late Harappan period, the Rigvedic people entered the Indian subcontinent. These pastoral migrants and their grazing animals came in from the west into the Indus Valley region in a phased manner.


The mitochondrial DNA studies tell a different story: that outward migration did not happen. Instead, they indicate that some of the social groups distributed in various parts of India share a common genetic ancestral lineage (designated haplogroup R1a1a) with eastern Europeans. The new archeogenetic papers suggest that haplogroup R1a1a mutated out of haplogroup R1a in the Eurasian Steppe about 14,000 years ago. Thus, these studies support the ‘Out of the East European Steppes’ theory. It follows from this that the original form of Indo-European languages was first spoken in Eastern Europe, the ‘original’ homeland.


The new study by Elise Kerdoncuff and her colleagues from the University of California, Berkeley confirms the origin of those ancestral groups by sequencing more than 2700 modern representative Indian genomes. The researchers also analysed previously extracted ancient DNA from groups with Iranian ancestry and compared it with the genes of modern Indians. Surprisingly the best comparison came from farmers from Sarazm in northwest Tajikistan. Farmers here grew wheat and barley, kept cattle, and traded extensively throughout Eurasia.


DNA from an ancient individual from Sarazm also carried traces of Indian ancestry. Interestingly, archaeologists were able to extract traces of ancient Indian ceramic bracelets from the burial sites in Sarazm. This is also an indication that trade and mixing were also taking place from the Indian side in those days. The Proto-urban Site of Sarazm illustrates the early rise of proto-urbanization in this region from the 4th millennium BCE to the late 3rd millennium BCE. Sarazm demonstrates the existence of inter-regional trade and cultural interchanges over long distances across Central Asia.


Archaeological evidence suggests that modern humans may have first arrived in the Indian subcontinent from Africa before or after the eruption of Toba volcano on the Island of Sumatra, 74,000 years ago generating the worst volcanic winter and disrupting human migration. Archaeologists have found stone tools from a site in the Son River valley in Madhya Pradesh. This forms the evidence of continuous human occupation at the site for the last 80,000 years.


The similarities of tool technology support the contention of the earliest eastward dispersal of humans out of Africa to India, which is now also supported by genetic studies. According to the new paper, some of the strong chromosome lineages are preserved in people from the Andaman Islands. The scientific evidence is clear about the fact that the Indian population carries a mix of genes borne by major migratory groups from parts of Africa, West Asia, Southeast Asia, and pastoralists from Central Asian steppes.


Genetic studies have recently provided us with a flood of data and established the fact that the human species evolves by a process of intermingling and interbreeding, not only between different population groups but also, at one point, with archaic hominin species like the now-extinct Neanderthals and the Denisovans. Genetic diversity is associated with increased fitness for survival and is a positive characteristic from an evolutionary perspective.

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