Southeast Asians derive ancestry from at least four different ancient populations, say scientists who analysed DNA extracted from 8,000 year-old skeletons and debunked two existing theories about the origin of humans in the area.
One theory believed the indigenous Hoabinhian hunter-gatherers who populated Southeast Asia from 44,000 years ago adopted agricultural practices independently, without the input from early farmers from East Asia.
Another theory, referred to as the 'two-layer model' favours the view that migrating rice farmers from what is now China replaced the indigenous Hoabinhian hunter-gatherers.
A study, published in the journal Science, shows that neither theory is completely accurate. Researchers discovered that present-day Southeast Asian populations derive ancestry from at least four ancient populations.
DNA from human skeletal remains from Malaysia, Thailand, the Philippines, Vietnam, Indonesia, Laos and Japan dating back as far as 8,000 years ago was extracted for the study.
Scientists had previously only been successful in sequencing 4,000-year-old samples from the region.
The samples also included DNA from Hoabinhian hunter-gatherers and a Jomon from Japan - a scientific first, revealing a long suspected genetic link between the two populations.
In total, 26 ancient human genome sequences were studied by the group and they were compared with modern DNA samples from people living in Southeast Asia today.
"We put a huge amount of effort into retrieving ancient DNA from tropical Southeast Asia that could shed new light on this area of rich human genetics," said Eske Willerslev, who holds positions University of Cambridge in the UK and the University of Copenhagen in Denmark.
"The fact that we were able to obtain 26 human genomes and shed light on the incredible genetic richness of the groups in the region today is astonishing," said Willerslev, who led the study.
"The human occupation history of Southeast Asia remains heavily debated. Our research spanned from the Hoabinhian to the Iron Age and found that present-day Southeast Asian populations derive ancestry from at least four ancient populations. This is a far more complex model than previously thought," said Fernando Racimo, an assistant professor at University of Copenhagen.
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