Mitochondrial evidence for the peopling of Australia
Analysis of mtDNA that includes full and partial coding region sequences in Aboriginal Australians from western New South Wales and central Australia identifies five major mtDNA haplogroups (van Holst Pellekaan et al in press). Haplogroup AuB belongs to global lineage ‘M’, and the others to ‘N’. Within N, AuA can be allocated to sub-division NS, AuD to NO, while AuC and AuE fall into N(R)P. The classification enables better evaluation of other published D-loop sequences. On available evidence SAuA, MAuB, PAuC and OAuD are widespread in Australia. To evaluate these data for the peopling of Australia, phylogenetic analyses have been carried out with other genome sequences including near neighbours. Australian sequences consistently fall into clades of predominantly non-Africans as in previous studies. Comparison with mt genomes of people from Papua New Guinea (PNG), Andaman and Nicobar Islands and Malaysia reveals that Australian haplotypes are distinct, linking only at the base of clades in phylogenetic trees. A few, including M and NP sequences group closely to some coastal and highland PNG sequences indicating ancient connection. However, the Australian MAuB sequences do not include any from the subgroup MQ that is common in PNG and Island Melanesia and which is purported to have expanded in the region (Friedlaender et al 2005, Merriwether et al 2005). Australian specific diversity indicates genetic isolation over a long period during which there was apparently very little gene flow between Australia, PNG and other near neighbours. Estimates of time depth using coalescent analysis and simple molecular clock calculations support continued presence of some deep maternal lineages in Australia for more than 40,000 years, while some are less distant from Eurasian lineages, suggesting the possibility of two major colonizing events. However, the story is complex and data from other areas of Australia would be required to test models of settlement properly.