New DNA research from an international team of scientists shows the ancestors of Aboriginal Australians and Papua New Guineans diverged from Eurasian populations between 51,000 and 72,000 years ago and that there is huge genetic diversity among Aboriginals.
The findings support the idea that humans spread out of Africa in a single event. The study, published in Nature magazine, is the first extensive investigation of Aboriginal Australians' complete DNA diversity, as previously only three Aboriginals had their full DNA sequences described.
The early peopling of Australia and its subsequent population history has been a matter of scientific debate for decades. The scientists, led by Eske Willerslev of the University of Copenhagen and in collaboration with Aboriginal co-authors, sequenced the genomes of 83 Aboriginal Australian and 25 Papua New Guineans, covering most of the Australian continent and the New Guinea highlands. (Until 10,000 years ago, Australia and New Guinea were joined.)
Aboriginal Australians and Papuans diverged about 37,000 years ago, long before the physical separation of the countries. The study found these people, coming from mainland Asia and travelling into Australia, were the ancestors of most if not all modern-day Aboriginals.
“The genetic diversity among Aboriginal Australians is amazing,” said Anna-Sapfo Malaspinas, first author of the paper.
“Perhaps because the continent has been inhabited for such a long time we find that groups from southwestern desert Australia are more genetically different from groups of northeastern Australia than are for example Native Americans and Siberians, and this is within a single continent.”
Whether modern humans left Africa in one or several waves has been much debated. The authors found Australian Aboriginals are mostly the result of a single wave out of Africa.
Professor Laurent Excoffier of the University of Bern led several key analyses in the paper. "Discussions have been intense as to what extent Aboriginal Australians represent a separate out-of-Africa exit to those of Asians and Europeans," he said. "We find that, once we take into account admixture with archaic humans, the vast majority of the Aboriginal Australian genetic makeup comes from the same African exit as other non-Africans."
Darren Curnoe, a specialist in human evolution at the University of New South Wales in Sydney, said the study "helps fill a major void in understanding the origins of two of the world's great populations – Indigenous Australians and New Guineans".
"This new work broadly shows that Australia was settled only once, without clear evidence for later migrations from far off places like India. This new work might finally mark the death of this unfortunate 19th-century idea," he said.
Aubrey Lynch, an elder of the Wongatha people and co-author of this study, said it has made important findings. "The result from this study confirms our beliefs that we have ancient connections to our lands and have been here far longer than anyone else. It also shows something of the depth and extent of our kinship connections across our land."