Southeast Asia is one of the most genetically diverse regions in the world, but for more than a century scientists have disagreed about which theory of the origins of this region’s population was correct.
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’ favors the view that migrating rice farmers from what is now China replaced Hoabinhian hunter-gatherers.
Professor Eske Willerslev from St John’s College, the University of Cambridge, and the University of Copenhagen and colleagues found that neither theory is completely accurate.
They discovered that present-day Southeast Asian populations derive ancestry from at least four ancient populations.
In the study, the team extracted DNA from 8,000-year-old skeletal remains from Malaysia, Thailand, the Philippines, Vietnam, Indonesia, Laos and Japan.
Scientists had previously only been successful in sequencing 4,000-year-old samples from the region.
The new samples also included DNA from Hoabinhian hunter-gatherers and a Jomon from Japan — a scientific first, revealing a long suspected genetic linkbetween the two populations.
In total, 26 ancient human genome sequences were studied by the researchers and they were compared with modern DNA samples from people living in Southeast Asia today.
“This study tackles a major question in the origins of the diversity of Southeast Asian people, as well as on the ancient relationships between distant populations, such as Jomon and Hoabinhian foragers, before farming,” said co-author Professor Marta Mirazón Lahr, Director of the Duckworth Laboratory at the University of Cambridge.
“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,” Professor Willerslev said.
“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.”
“The human occupation history of Southeast Asia remains heavily debated,” said co-author Dr. Fernando Racimo, from the Centre for GeoGenetics at the Natural History Museum, the University of Copenhagen.
“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.”
“By sequencing 26 ancient human genomes, we have shown that neither interpretation fits the complexity of Southeast Asian history,” said first author Hugh McColl, a Ph.D. student at the Centre for GeoGenetics in the Natural History Museum of Denmark at the University of Copenhagen.
“Both Hoabonhian hunter-gatherers and East Asian farmers contributed to current Southeast Asian diversity, with further migrations affecting islands in South East Asia and Vietnam.”
“Our results help resolve one of the long-standing controversies in Southeast Asian prehistory.”
The study is published in the journal Science.
Source : New Science | Sci-News | Smithsonianmag.com |