Valid. I will say the article states there were still hierarchical tendencies in the societies and leadership is mentioned in that society.

Other then that, How do we know that whether or not Aboriginals in Australia are the norm? Are they the norm or are they the exception. From my perspective the vast majority of societies have hierarchies and by virtue of being the majority it's strong evidence for hierarchies to be the more natural paradigm. Especially when paired with the biological evidence associated with serotonin and hierarchies.