> The Tasmanians were descended from Australian aborigines, and
> yet their
> technology level went down after they were isolated by rising seas.
> Their stone tools were far more primitive than those of their
> Australian
> ancestors. They ate shellfish, but didn't eat fish (they
> forgot how to
> do it). And yet they weren't brain damaged; they lost the
> knowledge of
> how to make better stone tools, and how to catch fish.
But if someone had turned up and taught them (no magic, just teaching) one
assumes they'd have been able to learn.