> But surely, the different tribes in Australia also moved around and replaced each other?

Read article, chase up the papers, evidence says "no".

The Tasmanians and the Noongars (Southern most to east, southern most to west) have genetically been in place a long time and had no one to replace.

The article mentions "genetic diversity" between east, west, centre, north, south, etc - that comes from not mixing.

"But surely..." <-- gut feelings? You should joinn Quadrant.

> If a tribe moved from southern Australia to the north and replaced another tribe

Do you have any evidence of that?

> who gets the land now?

There's a wealth of material on Mabo, Land rights, Native title, et al that address all that - if you're generally curious it's there to read.

eg: starting with, say https://aiatsis.gov.au/explore/mabo-case