I read this probably in the early 80′ maybe late 70’s. The title may in fact by Keyo but I can not find it anywhere. Keyo is a boy. Probably a Neanderthal. Or an early modern human. In the opening scene he leaves the cave. He hunts some small birds perhaps with a sling. He has a grandfather and sister(s). Later he takes part or witnesses a woolly rhinoceros hunt which I think involves a pit trap.