Even after someone figured out where it started – a dairy farm in Ohio – nobody could figure out how it went on, spreading from farm to farm. And nobody understood why, other than the fact they obviously liked the taste, that is.

Evolution bred them to chew and digest grass. They have big, flat teeth, not incisors or canines for ripping, sawing or tearing. They have stomachs nature had designed with ruthless, meandering efficiency to turn plant fiber into meat.

It may seem obvious to say nobody saw it coming. But nobody saw it coming. Their wild ancestors were herbivores and they were domesticated as such. As far as carnivores ought to have been concerned, they were food. We eat them: what part of that didn’t they understand?

The whole thing, I guess, once they got the taste. When the cows turned on us, it was a war for survival our kind hadn’t seen since we learned to poke at things with sharpened sticks. It was bad everywhere, worst of all in India, naturally, which was especially a betrayal.