Dear Terry Larch,
I always your article very interesting and logical.
So far as Australia is concerned, it is an island continent quite separated from the other continents with no land connection which might have been possible - not even temporary by freezing of sea water.
Perhaps that is why the animals are far too different from any other found in rest of the world.
Other continents have hens and cocks, Australia has Ostrich. Animals like Kangroos existed no where else but Australia.
Therefore logically human DNA of Aboriginal Australian an be different from others in the world. But perhaps unlike animals, humans could make rafts and use them to cross seas and reached Australia.