Comment by Tosh108

It's interesting that we have such a hard time accepting the emotion of altruism both in humans and animals. The author of the articles states: "could just be revenge". Revenge is in many ways more senseless then altruism for evolutionary purposes (unless you directly attack killer whales that threaten you, but one could argue that that's a form of self-defence), but from our ego perspective it feels more intuitive, at least to the author. There are also comments in this thread that reflect this way of thinking.