Thanks for your comment. I'd love to be able to answer you in more detail. I, and most Australians, know very little about the first nations of the land. I could probably give you more detailed answers on the politics of Weimar Germany than a general overview of Aboriginal culture.

This reference may give you some enlightenment in the difference between nations, cultures, and language groups.

The first two mins of this might help re language groups.

This is an interesting overview on potential Aboriginal agriculture. The section on the Bogong moth harvest might give some insight into how groups collaborated.

As has been mentioned, some of the Nation's of Indigenous Australia have continued cultures going back tens of thousands of years. It's harder to determine the exact history of any single Nation's history but there's a few examples.

The Budj-Bim Nation (south western Victoria) created a complex aquaculture system over 6,000 years ago, which remained in continuous use until the 1800s, when it was destroyed to make way for European farms.

The Budj-Bim people have since been able to reclaim the land, rebuild at least some of the aquaculture system and continue to maintain their language, religion, and cultural practices.

They by far are not the oldest continuous culture in Australia, but just one group I'd heard about recently. The greater cultural/language group has been on that part of Australia for something like 50,000 years.