The international study, published today by the Proceedings of the National Academy of Sciences, looked at genetic samples from populations across the region. The study detected a “substantial gene flow between Indian and Australia populations”, expected to have occurred more than 140 generations ago – roughly 4,230 years earlier.
The findings challenge the long held belief that Australia’s first people were geographically and genetically isolated from the rest of the world for almost 40,000 years before European settlers began to arrive in the 1800s.
“For a long time, it has been commonly assumed that following the initial colonisation, Australia was largely isolated as there wasn’t much evidence of further contact with the outside world,” said Professor Mark Stoneking, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
“It is one of the first dispersals of modern humans – and it did seem a bit of a conundrum that people who got there this early would have been so isolated,” Stonekig, the study’s lead author, added.
The team of scientists used genetic markers to compare DNA from Aboriginal Australians with DNA from people in New Guinea, South East Asia and India to identify which of the populations were more closely related.
An ancient genetic relationship was detected between the first Australians and New Guineans that goes back almost 45,000 years ago – a result which was expected, as Australia and New Guinea were once a single land mass, called Sahul.
What was unexpected, however, was a substantial gene flow between Australians and Indians – which raises more questions than it does answers.
The way in which the two peoples would have reached each other and the route they took, remains a mystery.
Professor Alan Cooper, from the Australian Centre for Ancient DNA at the University of Adelaide, believes that although the results were clearly unexpected, there are many significant changes that were taking place around that time which could support the theory of new migrants to the area.
“About that point in the archaeological record, there were significant changes in the use of stone tools, in hunting techniques and significantly, the introduction of the dingo,” Professor Cooper pointed out.
However he cautioned that, although the findings were logical, they were “based on a limited sample of genetic material.”
“It does not necessarily indicate direct contact with mainland India. For example it could be via populations elsewhere whose original source was mainland India,” Cooper argued.
An epidemic of new disease which wiped out earlier populations of Aboriginal peoples as well instigate a collapse of the Indigenous linguistic diversity, identified by ethnologists and linguists in South Australia, could have also been a result of an influx of migrants to the region.
“What it confirms is our lack of knowledge about human history in Australia, we have an incredibly long and rich human history that we know nothing about,” Professor Cooper said.
“It could be that Australia represents one of the longest continuous occupations of human culture anywhere in the world.”