[RightWhale]

extreme grizzly hunting is done on the ground with a long bow!...

There is an extreme problem with that. The arrow doesn't kill immediately. Further, a frontal shot is near impossible.

[wardaddy]

It was a joke for Squantos....I think that stuff is an urban (rural legend) however tribal folks have killed large predators with spears historically and not always in a group.

Did not Bill Hickock allegedly kill a grizzly with a knife in his early adulthood?

[Travis McGee]

What's the movie from a few years ago with the two guys surviving in Alaska after a plane crash? Fire-hardened spears against brown bears made a pretty good test. I think long strong spears would be better than bows. It's an interesting question.