People ask me why I'm so obsessed with ruminants. I've given it some thought, and my conclusion is that I'm not obsessed enough. A cow walks onto a wet hillside that grows nothing a human can eat, puts her head down, and comes back with steak, butter, cream and a pair of boots. She does it with a 150 litre fermentation tank she carries inside her, stocked with more bacteria than there have ever been people, which she feeds, waters and keeps at blood heat herself. Grass goes in. The bacteria take apart the one thing no animal can digest, and she lives on what they make. Then she digests the bacteria as well. Nothing is wasted. Even the fat comes out the far side rebuilt into something stable enough to fry in. Fuel: rain and sunlight. Emissions: next year's grass. She repairs herself, builds her own replacement every spring, and improves the ground she is standing on while she works. The finest engineers alive have spent billions trying to copy one chamber of her stomach in a steel shed, and so far they have made a paste. We have leaned on that machine for everything. The word capital comes from cattle, because a herd was the first bank. Domesday Book is written on sheep, and so was every deed in England for 500 years. Ruminants clothed our armies, lit our houses and carried our laws. Civilisation is a thing that happened to people who kept them. And they are such good company about it. A sheep remembers fifty faces for two years, which is forty-six more than I manage. A cow has a best friend, and her heart rate drops when that friend is beside her. A goat that cannot solve a problem will turn and look to you for help, as a dog does, and then ignore your advice. Let a herd out onto spring grass after a winter indoors and half a tonne of animal will skip. They ask for grass, rain, and to be left to get on with it. After ten thousand years of feeding, dressing and housing us, they will still walk over to the gate to see who you are. So no, I will not be calming down.

There is no other material on earth that can do what a fleece does, and it grows on an animal that eats grass. It keeps a sheep alive on a Welsh hill in February, in sleet, with no shelter. It keeps a Bedouin cool in the Sahara in August. It keeps a person warm when it is soaked through, which is why mountaineers wore it to the top of Everest. It will not burn. Put a match to it and it chars and goes out, which is why it lines aircraft seats and theatre curtains. It absorbs a third of its weight in sweat and gives off heat while it does it. It blocks the sun. A wool shirt has the ultraviolet rating of a decent sunscreen. It does not smell. The surface stays too dry for the bacteria that make a shirt stink. It stretches a third of its length and springs back, so a sock holds its shape for years. It stops sound. Recording studios and classrooms line the walls with it. It stops cold in a loft as well as fibreglass does, without the itch. It soaks up oil, which is why the mats laid on spills are made of it. It dyes deeper than anything, which is why a Persian rug is still red after 300 years. It felts into a tent that a Mongolian family lives in through a minus 40 winter. And when it finally wears out, it rots into fertiliser, and the next sheep eats the grass it grew. Every one of those jobs now has a synthetic doing it worse. The sheep had all of them covered before the chemist was born, and it does it again every spring for nothing.