dropoffyourkeylee : Bible thumpers aside, why were the aborigines so isolated? Did they not have any knowledge of boats? The Chinese and the Polynesians were travelling long distances, why didn't they touch Australia? There must be reasons for this
There certainly are reasons, the problem is that while one could think of possible reasons, it is almost impossible to verify them. Language is one way to attempt to work out how peoples moved, but it's only with the advent of genomics that it became possible to work out relationships. Likely we will never have all the answers as to what occurred.
The native peoples of Australia possible reached the Australian land mass during a period when a land-bridge existed between the Malaysian peninsula, through the Indonesian islands and N.W. Australia. If that occurred some 40,000 years B.P. and later ocean levels rose to the extent necessary to isolate these peoples, then we can see some reasons for the isolation. Aust. native peoples did not (it seems) develop the skills neccessary for large boat building. The earliest Europeans to reach Australia noted the types of water craft used by the native peoples and there does not seem to have been any observed large boats. But, we need to note that these people were not as primitive as some Australians of European descent have described.
A Wikipedia entry offers some of the theories that have been developed to explain the origins of Pacific basin peoples. You can find it at: https://en.wikipedia.org/wiki/Polynesians
When the entry speaks of Taiwanese, it does not mean the Chinese inhabitants, but refers to the earlier native Taiwanese people (descendants of whom still live in Taiwan)
See also: https://en.wikipedia.org/wiki/Taiwanese_aborigines) - Its theorised that the Polynesian peoples originated there. Note some similarities in this image:
The original peoples of Taiwan certainly had the maritime skills to make ocean journeys, as you see of some of them in the watercraft they still build.
This diagram illustrates one concept of migration.
and another slightly different concept:
You may also find this reference helpful:
ttps:/ /www.sciencedaily.com/releases/2009/01/090122141146.htm
Its also important not to conflate time periods. What people did 40,000 years ago is different to what people did 2000 years ago when the Chinese initiated coastal shipping and moving across the South China sea, and one thousand years ago when Polynesians began their voyages.