Brown bears don't generally like human, as I have found repeatedly when seeing them in the wild. Your fear is ungrounded and irrational. Step one: don't interact with bear. Step two: don't smell like dead animal. Neither of these are hugely difficult and are easy to grasp lessons.
At no point was predation a major problem for humans. Again, nutrition and infection would most likely dominate hunter gatherer mortality.
And yet a few people get killed by brown bears every year in glacier national park through no fault of their own.
Also as a PSA, playing dead works (better) for brown bears since they aren't so interested in dead things, never try that with a black bear who are more like scavengers. If you saw a bear in he states outside of northern Montana or Alaska (or yellow stone), it was just a black bear.
At no point was predation a major problem for humans. Again, nutrition and infection would most likely dominate hunter gatherer mortality.
How many remains have we found of mauled humans?