If you write about genetics and evolution, one of the commonest questions you are likely to be asked at public events is whether human evolution has stopped. It is a surprisingly hard question to answer.

I'm tempted to give a flippant response, borrowed from the biologist Richard Dawkins: Since any human trait that increases the number of babies is likely to gain ground through natural selection, we can say with some confidence that incompetence in the use of contraceptives...