‘Grazing is not just slightly inefficient; it is stupendously wasteful.’ Photograph: Peter Cade/Getty Images

What will future generations, looking back on our age, see as its monstrosities? We think of slavery, the subjugation of women, judicial torture, the murder of heretics, imperial conquest and genocide, the first world war and the rise of fascism, and ask ourselves how people could have failed to see the horror of what they did. What madness of our times will revolt our descendants?

There are plenty to choose from. But one of them, I believe, will be the mass incarceration of animals, to enable us to eat their flesh or eggs or drink their milk. While we call ourselves animal lovers, and lavish…