By Drew McLachlan
New research from the University of Huddersfield has unearthed details of India’s huge genetic diversity, with findings supporting the theory that local populations are descended from three major waves of ancient migration.
Led by PhD student Marina Soares Da Silva, the research used ancient and modern DNA samples to study migration patterns from 60,000 years ago to the Bronze Age, which ended roughly 3,000 years ago.
The first settlement in the Indian subcontinent, Da Silva explained, occurred shortly after humankind first left Africa, roughly 60,000 years ago, as hunter-gatherer societies began settling in the area.
The end of the most recent ice age, roughly 20,000 years ago, led to further waves of migration from Iran, along with the introduction of agriculture to the region.
Researchers also found evidence to support the theory that a third major wave of migration took place around 3,500 years ago, during the Bronze Age. This third wave originated from Central Asia, as mobile pastoralists from the area between the Black and Caspian seas headed further east.
This group are believed to have spoken what eventually became Sanskrit, the language of classical Hinduism, and were the first Indo-European speakers to settle in south Asia.
Details surrounding this third wave of migration, explained Da Silva, are “particularly controversial”, with many historians and linguists, “influenced by the long history of colonialism”, deny that immigration of Indo-European ever took place.
The lack of preserved skeletal remains, and therefore ancient DNA, from south Asia presents a major barrier to those studying these populations. As result, Da Silva and her team compared ancient DNA from central Asia, the Caucasus and eastern Europe with modern genetic patterns in south Asia, which were gathered from online repositories.
“Different genomes can be analysed in different ways, so in this study we compared different genetic systems,” Da Silva explained, “mitochondrial DNA for the maternal line of descent, the Y-chromosome for the paternal lineage and recombining nuclear DNA to give us a broader view of the genome (genetic material).”
There has been a “great deal of work” studying genetics in south Asia, Da Silva said, though this research has reached “contradictory conclusions”.
Further research into Y-chromosome variation, which tracks the male line of descent, provided strong evidence for this more recent wave of migration into India, one of the key takeaways of the research, Da Silva said.
“We were able to identify sex-specific genetic patterns and date the different dispersals into the (Indian) subcontinent. We have developed a chronology for the region’s settlement from the earliest Paleolithic arrivals, around 60,000 years ago, to the Bronze Age.
“The earlier arrivals have left a strong signal primarily in the mitochondrial lineages tracing the female line of descent, whereas the male line of descent is disproportionately represented in more recent episodes, especially the arrival of Indo-European speakers around 3,500 years ago.
“What is very interesting is that this scenario is very similar to what is known for Europe from the Paleolithic up until the Bronze Age, albeit with some differences in the time of some dispersals.”