“Stress, Portrait of a Killer,” a National Geographic production with Prof. Robert Sapolsky (www.youtube.com/watch? v=eYG0ZuTv5rs ) is very good and has a happy ending. It’s 44.23 minutes in if you’re in a hurry.

Prof. Sapolsky says he studies baboons because, “If you live in a baboon troop in the Serengeti, you only have to work three hours a day for your calories, and predators don’t mess with you much. What that means is you’ve got nine hours of free time every day to devote to generating psychological stress toward other animals in your troop.

“They’re just like us!...