Up to about 30% by many estimates. But the uncertainty bars are very wide. Would have varied enormously by season and ecotype.
Yes, I have seen patches of wild Nardoo growing here. And that's in AU, with the most miserly edible plant inheritance of any inhabited continent. Middle Eastern wheat and barley had much larger and more palatable seeds even before domestication.
Pre-industrial population densities were very low, and pre-agricultural even more so, didn't need large fields of monoculture.
