The Evolution of the Concrete Weir System

system because if it lasted that long in 40 000 plus years then they must have been when you see them managing it but I guess you mean they're also iterating it. There's evidence of that system evolving and growing over time of expanding and sort of contracting in terms of where the stones were being moved. It's also a system that existed through a period of European colonization of Australia so when Europeans first turned up in that set of river valleys in the 18 teams and 18 20s they saw the weirs and knew that Aboriginal people had fish there.