Economists and biologists used to insist that humans are mainly driven by self-interest, with cooperation just a way of using others to get more for ourselves. That view was undermined by modern experiments showing that most of us also care about fairness and justice for others. Now research is pointing to another, more spiteful side of human nature. We care about fairness, but also about knocking others down, even at a cost to ourselves.
It is clear enough that animals can encourage the perpetuation of their own genes into future generations by helping their close relatives. Altruistic behaviour can…
