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.
There’s a book called ‘Keo, the cave boy’ by Lois Hamilton Fuller, (1961). Here’s the Kirkus review: Children of the twentieth century will be enlightened not only on the vast differences between their lives and those of prehistoric cave children, but also on the similarities that must have existed from time immemorial. Living with his family, Keo must remain with the women and children though he longs to hunt with the men. His life takes on interest and excitement when he befriends Hago, a boy his own age, and the two exchange skills. Hago, an expert fisherman, is responsible for the admiration Keo receives when he brings home his first excellent haul. While the men of the tribe deal with the thrills and dangers of conquering wild animals, Keo and Hago encounter their own perils, saving each other from drowning in quicksand, spearing fish and birds, keeping watch. They have their knock-down drag-outs as well, but their friendship is too strong to be dissolved over the ownership of a bird. Famine rears its ugly countenance and the cave people journey far across the snow in search of food and new homes. In an untried cave, Keo and Hago protect the women and children from an attacking bear and are finally accepted as full fledged men in an impressive ceremony. The customs depicted have apparently been well researched increasing the value of an intriguing story.
This is it! Thanks!