[Eggsellence]

How certain can we be that those groups hadn't simply reached the limits of their capacity for expansion?

Aboriginal Australians have one of the lowest average IQs of any ethnic group on earth, they had little to no concept of agriculture or weaponry, and existed in relatively small disjointed tribes rife with infighting and appalling violence in an unforgiving climate.

Were these people capable of organising, planning, equipping, strategising, and executing an assault on their neighbours? Would it have even been worth it - what would they gain? Even if capable, they may have been wisely unwilling.

I think it's incredibly naive to think that a capable tribe of Aboriginal Australians would have left their defenceless neighbours in peace if they stood in the way of valuable resources. Or that this didn't indeed occur countless times in relatively small skirmishes.