11 May 07

Scientists studying the origins of Australia's aboriginal population have found no genetic evidence of significant immigration from outside the continent for 45,000 years after humans first arrived. Their research suggests that Australian aborigines share the same common ancestor with all other human populations: so-called 'mitochondrial Eve', who is believed to have lived in Africa between 150,000 and 200,000 years ago.

This new study overturns previous population genetic papers on mitochondrial DNA and Y chromosomes from Australian aborigines which suggested that contemporary aborigines derive from migrants arriving from India as recently as 5,000 years ago.

The research team traced the Y chromosomes and mitochondrial DNA of the modern aboriginal population. They found that the types of mitochondrial DNA and Y chromosomes present in aboriginal people from Australia and New Guinea are all from ancestors who left Africa at least 45,000 years ago. The findings strengthen the idea of an African origin for all living humans - the 'Out-of-Africa' theory - as opposed to multiple origins both in Africa and elsewhere - the 'Multi-Regional' theory of human evolution.

Mr Phillip Endicott of Oxford University, co-author of the study, said: 'Our work also suggests that cultural changes that took place during the last 6,000 years, such as the development of new technologies and the introduction of the dingo, do not seem to have been mediated by any significant migration from other locations. This does not mean that some small incidences of immigration did not occur, just that they left no lasting impact on the maternal and paternal lineages of the region.'

This research will soon be complemented by studies of ancient DNA obtained from historical samples relating to the early phases of colonial occupation of regions from India to Australia. In many cases the populations are now extinct and anthropological collections are the only way to reconstruct this lost genetic diversity, which can be vital to understanding the past. This research, conducted by Mr Endicott, will provide further significant insights into the pre-history of the region and the human exodus from Africa.