George Langford
Senrac the Lion Man
From the dustjacket:

Here is fascinating history and amazing adventure — the kind that youth is always searching for. You will live with Senrac, the Lion Man in the Stone Age as a member of the primitive village from which this exciting story unfolds.

Senrac, when a baby, was stranded together with a lion cub on a floating island. Strongly attracted to the foundling, his finders adopt him and return to their village with both boy and cub, whose closeness to each other grows as they both grow. Senrac's ingenuity and skills, his new rope traps, his strength in hand-to-hand combat with wild animals and his love and understanding of all living things result in the community's choosing him as their leader.

The mystery of Senrac's real parents and background is dimmed by his popularity, but it is later exposed through the maliciousness of Abra, a jealous leader of mother tribe, who spreads the rumor that Senrac's mother was a lioness, pointing to his lion-like coloring and features and his strong affinity for animals. The unrest and doubt which follow set off a series of exciting events.

Primitive man, too, required friendship, love, affection and cooperation between himself and others in order to survive. SENRAC, THE LION MAN is an authentic, exciting and challenging adventure into the Stone Age that will long be remembered by the many thousands of boys and girls who will love this book.