Bonnie Pryor
Seth of the Lion People
1988
from the dust jacket:

When Magli, Teller-of-Stories, was leader of the Lion People, he made certain that the cave dwellers never forgot their beginnings or the wisdom that helped them survive. For a time it seemed that Seth, crippled from childhood, would follow in his father's footsteps.

Suddenly Magli is leader no more and Seth faces a barrage of taunts — "old one leg" — led by the new leader's cruel son. Seth fears that even if, as his dying father intends, he should succeed Magli as Teller-of-Stories, he'll have little value in a clan that now measures a man's worth by his hunting and fighting skills. Perhaps he'd fare better beyond the mountains that had always rimmed the Lion People's world...

So Seth sets off, with his best friend, Esu, and the loyal Dog, to see if the most extraordinary story of all is true: that over the mountains are people who tend crops, domesticate animals, and live in warm huts, not caves. Seth of the Lion People is a richly textured novel of a young boy's journey to self-discovery at once a page-turning adventure and an intriguing portrait of our unrecorded past.