More intriguingly, an experiment carried out in 2004 by Brian Hare, then at Harvard and now of Duke University in North Carolina, suggested that natural selection in the context of domestication had boosted dogs' intelligence, too, by allowing them to understand human behaviour in a way that their ancestors, wolves, cannot.

ECONOMIST: Wolves are, after all, cleverer than dogs

The ocean is a single, contiguous body of water that is crucial to human life: an unauthorized experiment carried out in one place can have consequences hundreds of kilometres away.

UNESCO: MEDIA SERVICES

In the 1960s, the American government carried out an experiment known as Project Storm Fury.

ECONOMIST: Saturday-night showers