What happens in the ending of "By the Waters of Babylon"?

At the end of this story, John brings back all of the things that he learned on his journey.  The ending is all-important, because it reveals what happened to the people who died generations ago, and John, in a vision, is revealed great truths to bring back to his tribe.  He sees the demise of the ancient people, and understands fully why they died.  How will he handle this information?  He goes back to his tribe, and has the desire to tell them everything that he learned, and to reveal it all right then and there.  However, he speaks with his father first.  His father, a wise priest in their tribe, offers the following very sage advice:

"He said, "Truth is a hard deer to hunt. If you eat too much truth at once, you may die of the truth. It was not idly that our fathers forbade the Dead Places."

What his father meant by this was that truth is something that is good, but only in small doses.  Sometimes, we have to gain knowledge, information and truth slowly, so that we can learn to use it wisely, and control the power that it gives us in wise ways.  Think of a child, and how he or she is progressively allowed to do things as they grow up.  If they were allowed to do everything right away, they would cause a lot of damage and harm, because they aren't developmentally ready for it yet.  John agrees with this assessment that his father gives, and concludes that the ancients "ate knowledge too fast."  He decides to reveal things to his tribe slowly, carefully, and wisely, ensuring that the information is appropriate, understandable, and at the right time to be used wisely. I  hope that those thoughts helped; good luck!