[Foxbat]

My own take on the ending was that it was another step - but also the story had gone full circle. The ape at the beginning gains an advantage (and step forward) by using the bone. Ditto the Starchild who gains an advantage (and therefore an evolutionary step forward) with his new powers.

It's many years since I read The Sentinel but, from what I remember, it covers the finding of the Monolith on the Moon. It's around here somewhere........