Australasian Science: Australia's authority on science since 1938

Aboriginal Genome Reveals New Insights into Early Humans

By Australian Science Media Centre (Ed.)

What does the genetic sequencing of an ancient Aboriginal man tell us about the ancestry of Aboriginal Australians?

“It definitely strongly supports the idea that Aborigines were an early and separate wave of human expansion out of Africa, before the subsequent wave that established Europeans and Asians. This has long been thought to be the case, due to the very early archaeological signs of Aboriginal presence in Australia (~50 kyr) and existing genetic data, but the highly resolved view available from a genomic sequence is a really valuable contribution. While the information is only from a single individual, it provides a powerful view of the common, shared heritage of the movement of the ancestors of modern Aboriginal populations from Africa around half the world to Australia – which is one of the most important and poorly understood stories of human history.

“The key unresolved question remains the unique story of Aboriginal history within Australia. Unfortunately, the information from a single individual tells us very little about this critically important part of human history. Aborigines are one of the oldest continuous human populations outside Africa, and due to the geographic isolation and limited archaeological records – remain one of the most mysterious chapters in human history.”

Professor Alan Cooper is Director of the Australian Centre for Ancient DNA at the University of Adelaide.

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“This new DNA study powerfully confirms that Aboriginal Australians are one of the oldest living populations in the world, certainly the oldest outside of Africa. Their ancestors evolved on the African continent and were the first modern humans to arrive in Asia, the work confirming they have occupied Australia continuously since that time, perhaps 70,000 years.

“Australians are truly one of the world’s great human populations and a very ancient one at that, with deep connections to the Australian continent and broader Asian region. About this now there can be no dispute.

“The study also confirms controversial claims that the ancestors of all living Eurasians interbred with the Neandertals, while past Asians/Oceanians also mated with the mysterious ancient humans from Denisova cave in Siberia. This is clear and independent validation of DNA work on both these extinct humans, confirming their deep connections to Australians and other indigenous people in our region.”

Associate Professor Darren Curnoe is leader of the Human Evolutionary Biology Lab at the University of New South Wales.

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“Ancient DNA studies of entire genomes are having a profound impact on how we tease apart our shared human ancestry, ranging from Neanderthals to ‘Denisovans’ and different populations of Homo sapiens. How much history we all ‘share’ with each other is a moot point, and subtle differences can be surprisingly revealing about the timing and the routes of ancient human dispersals.

“Aboriginal Australians and New Guineans have long been under-represented in global surveys of human DNA, so Rasmussen and colleagues sequenced the genome of an Aboriginal Australian from a century-old lock of hair. They found that this man was part of a population that had split perhaps 75,000 to 62,000 years ago from the other groups of Homo sapiens that had also exited Africa in the initial, single dispersal event. The subsequent expansion into Asia most likely occurred in multiple waves, with the Aboriginal Australian being descended from the first wave to wash onto Australia’s shores.

“The timing of the genetic split, before 62,000 years ago, fits neatly with the initial colonisation of Australia and Papua New Guinea some time between 60,000 and 45,000 years ago, based on archaeological discoveries such as stone tools and human fossils. The existence of Denisovan DNA in the Aboriginal Australian’s genome indicates that the original dispersing population of Homo sapiens must have encountered resident Denisovans en route to Australia, possibly in New Guinea. So we now have the intriguing possibility that the island chains leading to Australia were home to the last surviving members of Homo erectus on Java, ‘hobbits’ (Homo floresiensis) on Flores, and Denisovans in New Guinea – and that some or all of these were met by the ancestors of the Aboriginal Australian whose hair was sequenced in this study.”

Professor Richard ‘Bert’ Roberts is Director of the Centre for Archaeological Science at the University of Wollongong.

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The authors have at their disposal a single genome that is to a large extent reconstructed from degraded fragments. The authors admit this limitation, but then proceed to produce a grandiose discussion on the peopling of Asia and Australia, making pronouncements on the number of migration waves and links to Denisovans and Neandertals. Yet again, the directional forces of evolution are ignored (mutation and natural selection) and the analyses are couched in terms of only migration and isolation of populations as if evolution did not take place. Comparing genomes possibly separated by some 60,000 years, as the authors admit, would have to consider that mutations and natural selection may have altered genetic material.

“It stands to reason without any analysis that continents, including Australia, were not settled by one wave of migration over tens of thousands of years. Archaeological record and historical information indicate that people move all the time and get to new places settling there or mixing with locals. What is new about it?

“The paper may be showing off technical prowess of authors at genetic analyses, but intellectually it adds very little to our understanding of the peopling of Australia.”

Maciej Henneberg is the Wood Jones Professor of Anthropological and Comparative Anatomy at The University of Adelaide.

Source: AusSMC