Charles Willard Diffin
The secret of the sun-god's cave
1942
from the dustjacket:

This is the thrilling story of Rak, a boy who lived in a cave at the edge of the jungle long ago when the world was young.

At Rak's birth, the wise woman of the tribe made a strange prophecy. She said that he would travel to far-off places, even to the end of the world where the Sun-god slept, and that he would be chief of two tribes. But whether he would ever come back to his own caves, she did not tell.

As Rak grew up and learned to hunt with the long spear, he found adventure waiting for him at every turn of the forest trails. Sometimes it was a tree-cat waiting to spring. Once it was a horde of wild ape-like invaders that fell upon the tribe; and once, Mum-boob, the great savage bear.

By the time his journey to the end of the world began, Rak had already rescued his people from destruction. And he found out what no cave dweller knew before — that a raft made of logs could carry a whole tribe down the river to safety.

That was only the beginning of his discoveries. Together with his friend Poto and his dog Ghee, Rak set out on unexplored trails. The prophecy was right. For Rak's way took him to the Sun-god's cave, and he came back to share with his people the wonderful things he found there.

Beautifully written, with characters strongly portrayed, THE SECRET OF THE SUN-GOD'S CAVE makes this far-off period extraordinarily alive to boys and girls of today.