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.

2017 could be even bumpier. There will be at least three elections in Europe next year: in Germany, France and the Netherlands for sure, and now perhaps in Italy, too. Just about everywhere, political establishments are being blamed for tepid growth, for too few jobs and for favoring global financial markets over the common citizen.