Why are warriors capable of working together, although they like fighting with each other?

Men have a long history of fighting with one another for dominance, but why such duels did not leave tribal unity in tatters and warriors less capable of working together to fend off attacks from predators and hostile clans remains a mystery. One common theory is that men more readily make up after fierce physical conflicts than do women. And an experiment run recently at Harvard University suggests this may be true.

Workers are promised something called a defined-contribution pension which, truth be told, isn’t a pension at all. It is a savings pot to which employers and employees contribute, with some tax advantages. How big that pot will be, and what kind of income it will provide, is unknown.