Keith Wardlow

A boy takes in a stray dog, later finding out that its an ultra-intelligent runaway from a genetic research lab. Unbeknownst to him, the dog is being stalked by another escaped creature thats not quite so friendly.

Natural changes have the clans moving. Iza, medicine woman of the "Clan of the Cave Bear" finds little Ayla from the "others"' clan - tradition would have the clan kill Ayla immediately, but Iza insists on keeping her. When the little one finds a most needed new cave, she's allowed to stay - and thrive.