There is good evidence of a high Aboriginal population density at contact. Australia has a naturally occurring diversity of plant resources, rather than a few specific staples as in Papua New Guinea. These are easier to exploit if not planted. That is to say, Koori people are Polyculturists. The population may have been increasing at the time of the invasion. Butlin has calculated that the population certainly did not survive on kangaroos alone as a meat source. If 15% were killed to maintain a stable population, that is, a hunter killed more than 1 per year, ‘roos would have been extinct in 10 years. Therefore Kangaroos did not provide enough protein for the relatively high number of Koori people living in the Sydney region at the time of the invasion. Kohen p 81.
‘From what we can glimpse, the closest links and associations between Sydney clans and bands seemed to run north-south along the coast, rather than east-west between the coast and inland mountains. Rivers and creeks, were food was more abundant, were the places of densest occupation, while high places were for ceremonial use. Rivers served as both boundaries and corridors. Karskens, The Colony, p. 42.