The article mentions that human artefacts have been found in the sediment under the solidified lava from the eruption of the said volcanos.

It also appears to claim that Australia seems to be a general exception to the rule that human populations move around - in this case they appears to have stayed put. As a result, it’s a reasonable deduction that there were humans before the said volcanoes, and (less credibly) that they are generally linked to the aforementioned indigenous population. Ultimately I think what’s interesting is the first part, a piece of human culture survived for so long through whatever means.