New York: Modern humans did not enter the Indian subcontinent until after the supervolcanic eruption of Mount Toba in Sumatra nearly 75,000 years ago, according to new research which dispels a previous idea that humans arrived much earlier in the region.
The findings suggest humans left Africa to arrive in South Asia around 55,000 to 60,000 years ago, long after the Mount Toba supereruption 74,000 years ago.
This contradicts some archaeologists` claims that modern humans have been living in the region for twice that long.
The research used a combination of archaeological and genetic data to suggest the new earliest possible date for the exodus from Africa to Asia, `LiveScience` reported.
"The ash from the eruption, which was an absolutely huge eruption, blew across all of India and smothered the whole region in ash," said study co-author Martin Richards, an archaeogeneticist at the University of Huddersfield in the UK.
"Modern humans weren`t there when that happened. They arrived afterwards," Richards said.
Most archaeologists believed humans migrated to what is now India between 50,000 and 60,000 years ago. However, in a 2007 study, archaeologists reported on stone tools unearthed in Jwalapuram in southeastern India both above and beneath the ash layer deposited by the Mount Toba supereruption about 74,000 years ago.
That mega eruption spewed enough lava to create two Mount Everests and blocked sunlight for years.
One researcher argued that the tools looked similar to those used by modern humans in Africa at that time, which suggested that modern humans were in South Asia prior to the volcano eruption. Some even proposed that the migration might have happened as far back as 130,000 years ago.
To test the idea that humans reached South Asia before the eruption, Richards and his colleagues analysed 817 samples of mitochondrial DNA, which is carried in the cytoplasm of the egg and is only passed on through the maternal line, from people throughout the subcontinent.
They then compared it with existing samples from East Asia, the Near East and sub-Saharan Africa.
The genetic evidence suggested that people emerged in the subcontinent via the western coast between 55,000 and 60,000 years ago, well after the eruption.
These ancient humans appear to have colonised the coasts of the subcontinent first, and then spread into the interiors along rivers, Richards told the website.
In a separate research, archaeologist Paul Mellars of the University of Cambridge in the UK and his colleagues analysed the stone tools in Jwalapuram and compared them with stone artifacts from both other regions in the subcontinent and Africa.
The team concluded that the tools from before the eruption did not resemble those used in Africa during the same period and, therefore, weren`t made by modern humans. Instead, archaic humans - possibly Neanderthals - probably made the tools, Mellars told the website.
The study was published in the journal Proceedings of the National Academy of Sciences.