Who were the first Australians

Task: Critically assess the evidence for two genetically separate human populations on the Australian Continent during the Pleistocene.
Please note the current view in Australian Archaeology is based on the Out of Africa theory and that there was in fact only descendants from Homo sapiens in Australia during the Pleistocene. But some researcher believe some evidence/fossils point to a separate species such as the Homo erectus also arriving in Australia during the Pleistocene. Please assess this evidence that there was possibly more than one species, but arrive at the conclusion that there was in fact only one (Homo sapiens).