Being British, I have a naturally mischievous streak and one of the things I occasionally enjoy is gently poking students with the sharpened end of a question to get a reaction. This can easily be done with the aid of a whiteboard and a marker pen. Draw a large circle on the whiteboard and say to the class something like: “This circle represents the entire set of genomes of every living thing on planet Earth. Everything is here, from whales to whelks, ants to antelopes, bacteria to bats, hippopotami to humans.”

Now I ask the class a further question: “Raise your hand if you do not believe in human rights?” Rarely will a hand go up (peer pressure can be a wonderful thing). “Excellent!” say I, taking my pen and drawing a second, much smaller circle, within the bigger circle. “Now what those of you who believe in human rights are saying is that anybody who lives inside your smaller circle, whose genome is ‘human’, enjoys a special set of rights that inhabitants of the bigger circle do not. Agree?”

Again, rarely will anyone protest.

“Wonderful,” I enthuse, rubbing my hands together in anticipation of what is about to follow. “So here’s the problem. Along comes the white supremacist, armed with a marker pen of his own, and he draws a much tinier circle within your small circle and says, ‘No, only those who are white and European enjoy full rights. Any other races do not.’. See the problem? You have drawn a circle, he has drawn a circle, you have both drawn circles. So tell me: why is your circle acceptable (even laudable, as the we give awards to people who defend human rights) but the circle drawn by the racist is not?”

Usually, there is a stunned silence at this point.