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.

Air-conditioning doesn’t feel like much of a luxury in parts of India, but the taxman begs to differ. Cooled restaurants are deemed posher. Luckily for sweatprone diners there is a catch: the tax only applies to the service and not the food, so only part of the tab incurs the extra levy. In their wisdom, India’s bureaucrats once decided that 60% of a restaurant’s offering is food, and so air-conditioning triggers a service tax payable on just 40% of the bill.