That seems basically impossible. Salt is really easy to find many places, its taste is _very_ obvious, and it's insanely useful (preserving food). I'd buy that

That seems basically impossible. Salt is really easy to find many places, its taste is _very_ obvious, and it's insanely useful (preserving food). I'd buy that we don't have great _evidence_ of its harvesting before that, which seems more like what the article says? But that's not really the same thing at all.