Aboriginal Australians have been genetically isolated from the rest of humanity for 50,000 years with no direct evidence that they had ever intermarried with South-East Asians about 4,000 years ago, as some scholars have suggested, a DNA study has revealed.
A detailed analysis of the male Y chromosome from 13 Aboriginal men found no traces of DNA from other ethnic groups, such as people from the Indian sub-continent who were thought to have migrated to Australia about 2000BC.
Geneticists have calculated from mutations present in the Aboriginal Y chromosome that the first inhabitants of Australia had separated from other members of Homo sapiens living elsewhere in the world about 50,000 years ago – probably long before our species had arrived to live in Europe.
The findings of the study, however, fail to explain the arrival of the dingo wild dog in Australia, which is not a native species and was almost certainly brought by humans to the continent from other parts of south-east Asia.
Previous genetic studies, along with archaeological evidence of imported tools and a change in language, had suggested that the dingo had arrived with south-east Asians who had settled in Australia and interbred with local Aboriginals.
However the latest study, published in the journal Current Biology by an Anglo-Australian team of researchers, rules out any interbreeding with non-Aboriginals, at least down the male line of descent, said Chris Tyler Smith, an evolutionary geneticist at the Wellcome Trust Sanger Institute in Cambridge.
“We have disproved interbreeding with south-east Asians at least for the Y lineage of the male chromosome but we have not yet been able to prove that it had not happened in the non-Y lineage – but it seems unlikely,” Dr Tyler Smith said.
It was known that Australia and Papua New Guinea – geographically known as Sahul – were populated very early in human history, but the extent of the geographic and genetic isolation is only now becoming apparent with genome analysis.
“We have discovered that there is a very deep, 50,000-year-long history that is specific to the Y-chromosome of Aboriginal Australians. This deep split essentially shows we have two rungs of human evolution after 50,000 years – one in Sahul and one in the rest of the world,” Dr Tyler Smith said.
The researchers liaised closely with Aboriginal communities to carry out the DNA analysis and have already shared their results with them, he said.
“We were effectively telling them what they already knew. They were the least surprised by the findings,” Dr Tyler Smith said.
Lesley Williams, an Aboriginal elder, said that “science has confirmed what our ancestors have taught us over many generations – that we have lived here since the Dreaming”.
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