A boundary is a boundary, whether it is a fence, a sign , or a rock stack. The stacks do indeed define the boundary between river systems, each river system seems to have had individual family groups. That assumption is based on the difference in the design of the tools and lizard traps in that particular region. The tools we have found are quite stunning in the workmanship -- try to make one -- and the traps vary in many ways too.
Some have a single rock propping them up, others have two, some three etc.
If the rock stacks truly are man made boundary delineators then the entire legal case of terra nulla is a farce, which means of course, that the settling of land here was illegal .
