Hmmm...IIRC my interpretation of the book was that at the end he was supposed to be the "starchild-messiah" thing who brought the knowledge of aliens to the humans in a way that wouldn;t blow their minds and save their species, preparing them for the stars. and didn't he end the nuclear war that was about to erupt on earth by his presence. SO he was a signal that humans ain't alone, and, I would think that because the humans simply coulnd;t fathom the aliens - too advanced for our minds to handle, etc...? But, really, this is all going from memory. And, I never read the Last book but by then I think the aliens had given up hope on humanity, after they had brought them up from the apes and given them technology, the humans still didn't get it, so they were going to wipe them out, or something like that?