Much of human history comes back to just two things, water and calories, both linked to geography.
Water is critical for drinking and for food supply. Availability of calories determines the population that can be supported and at what standard of living.
The western slopes and plains are marked by long dry periods. During these periods, the Aboriginal populations concentrated around permanent water supplies as free-standing water elsewhere disappeared. Then with rain, they foraged more broadly.
As you would expect, there is a clear correlation between population densities and calorie (food) availability. High coastal populations were supported by a variety of aquatic and land food resources.
When I first looked at Aboriginal population densities in New England, I focused especially on settler records recording numbers of Aboriginal people. While this indicated that numbers were higher than had been realised and provided, I think, a reasonably accurate picture of relative population densities over the whole area, the approach was subject to a whole range of weaknesses.
A better way might be to look at calories.
Start with the quantity of calories required to retain life. This needs to be adjusted for the fact that the Aborigines were active in physical terms. Then what was the calorie availability like in particular areas taking seasonal factors into account?
At least two further things need to be factored in.
The first is the human need for variety not just in food, but in personal interaction. We already know that the availability of food surpluses led to gatherings of peoples for trade and other joint activities. However, we (certainly I) tend to know only major events because these were the only ones recorded in the historical record. There were certainly many others.
Intuitively, the pattern of interaction changed with increased calorie richness. This did not necessarily mean more interaction in an aggregate sense - sedentary people living in a rich environment may interact less. However, interaction is likely to be different simply because the pattern of food surpluses is likely to be different.
The second is the fact that people eat to live, not live to eat. By this I mean that in a day to day sense people would spend that amount of time gathering or hunting food that was required to meet their needs.
Anthropological research in the Northern Territory, I cannot remember the reference at this distance in time, suggested that the people being studied spent a bit over six hours a day collecting food. The rest of the time was available for other things.
I make this point because I have the strong impression that actual population densities in many places were below the theoretical maximums that would have been allowed by available food supply.