The foundation for 2001: A Space Odyssey and its numerous sequels is an intelligent, long-lived, race of space-travelers incapable of staying in any solar system for any length of time, but capable of offering help to species they think of as promising. Apparently, as the post title, cribbed both from that work and from 3001: The Final Odyssey, sometimes species that failed to live up to their promise had to be culled: these space-travelers couldn't always count on an unexpected supernova or an asteroid to end the experiment. Book Review No. 20 deals with 3001. I do not wish to publish any spoilers. Let me pose a question, though: would a race that puts an alarm in a place that only a species capable of space travel be pleased or annoyed should that same species figure out that a weeding operation is about to commence?
(Cross-posted to 50 Book Challenge.)