New Guineans and Aboriginal Australians descend from two groups of settlers who arrived 60,000 years ago

The first settlement of New Guinea and Australia by modern humans took place some 60,000 years ago, according to new findings of a major research collaboration between the University of Southampton and the University of Huddersfield.

The genetic research reveals two distinct groups of settlers dispersed into the region from different parts of what is now South East Asia.

The study, published in the journal Science Advances , is a collaboration between archaeogeneticists, archaeologists, earth scientists and oceanographers. It clarifies the much-debated who, where and when of this early maritime migration.

The work was funded by a European Research Council grant to Professor Helen Farr of the University of Southampton’s Centre for Maritime Archaeology , with the archaeogenetics team led by Professor Martin Richards at the University of Huddersfield’s Archaeogenetics Research Group.

During the last Ice Age, when sea levels were much lower than they are today, New Guinea and Australia were part of a single landmass, known as Sahul. There has been a long-running discussion about both the timing of the first settlement of Sahul and the routes by which people first travelled to the ancient super-continent.

It is widely known that the ancestors of New Guineans and Aboriginal Australians have inhabited Sahul for tens of thousands of years, with many Aboriginal Australians understanding that they have always been ‘on country’.

However, for western scientists and archaeologists, the details of global dispersals have remained controversial.

There are two views on the timing of the settlement – the ‘long chronology’, suggesting that the first settlement goes back to around 60,000 years and the ‘short chronology’, which argues for a first landfall around 45,000 to 50,000 years.

The interdisciplinary team, including colleagues at the University of Minho in Portugal, at La Trobe University in Australia, and the University of Oxford, focused firstly on human mitochondrial DNA (mtDNA) genomes to address this question. The mtDNA is inherited only from the mother, and the way the mtDNA sequences vary from one person to the next can therefore be used to recreate the maternal genealogy in great detail.

The team analysed almost 2,500 mtDNA genomes from Aboriginal Australians, New Guineans, and people from the western Pacific and Southeast Asia. They used these to build a genealogical tree and looked at the way the lineages in the tree were distributed from one population to the next. As all DNA changes gradually over time, they used the amount of change in the lineages – known as the ‘molecular clock’ – to date lineages from each region.

Their findings showed that the most ancient lineages seen either in Aboriginal Australians, New Guineans, or both, but nowhere else, dated to around 60,000 years, coming down firmly in support of the long chronology.

The ancestry of the most ancient lineages could be traced back to Southeast Asia. But the team also found that while the majority traced back to more northerly parts of Southeast Asia – northern Indonesia and the Philippines – a significant minority traced to more southerly parts – southern Indonesia, Malaysia and Indochina. This suggested there were at least two distinct dispersal routes into Sahul with lineages from both routes dated to around the same arrival time.

Southampton’s Professor Helen Farr comments: “This is a great story that helps refine our understanding of human origins, maritime mobility and early seafaring narratives. It reflects the really deep heritage that Indigenous communities have in this region and the skills and technology of these early voyagers.”

The work is especially significant as although the new genetic results fit well with the archaeological and palaeoenvironmental picture, in the last few years many geneticists have been moving in the opposite direction, towards a short chronology

Professor Martin Richards said: “We feel that this is strong support for the long chronology. Still, estimates based on the molecular clock can always be challenged, and the mitochondrial DNA is only one line of descent. We are currently analysing hundreds of whole human genome sequences – 3 billion bases each, compared to 16,000 – to test our results against the many thousands of other lines of descent throughout the human genome.

“In the future there will be further archaeological discoveries, and we can also hope that ancient DNA might be recovered from key remains, so we can more directly test these models and distinguish between them.”

The work is published in the American Association for the Advancement of Science’s journal  Science Advances. A companion paper by a similar interdisciplinary team including both Professor Richards and Professor Farr and led by Dr Pedro Soares of the University of Minho, used to check the accuracy of the molecular clock data, was published in October in the journal Scientific Reports.